Attached please find a patch to the input parser that yields better
syntax error reporting on parse errors. For example:

test=# SELECT * FRUM bob;
ERROR:  parser: parse error at or near "frum"

becomes:

test=# SELECT * FRUM bob;
ERROR:  parser: parse error at or near 'frum':
SELECT * FRUM bob;
         ^

I've also modified the regression tests accordingly.

I haven't made the corresponding changes to the ecpg grammar -- I'm not
sure whether changes like this are desirable there. Feedback welcome.

Comments?

Neil

-- 
Neil Padgett
Red Hat Canada Ltd.                       E-Mail:  npadgett@redhat.com
2323 Yonge Street, Suite #300, 
Toronto, ON  M4P 2C9

Index: src/backend/parser/scan.l
===================================================================
RCS file: /home/projects/pgsql/cvsroot/pgsql/src/backend/parser/scan.l,v
retrieving revision 1.88
diff -c -p -r1.88 scan.l
*** src/backend/parser/scan.l	2001/03/22 17:41:47	1.88
--- src/backend/parser/scan.l	2001/08/01 17:43:53
***************
*** 37,42 ****
--- 37,43 ----
  
  extern char *parseString;
  static char *parseCh;
+ static int parseOffset;
  
  /* some versions of lex define this as a macro */
  #if defined(yywrap)
*************** other			.
*** 254,262 ****
   */
  
  %%
! {whitespace}	{ /* ignore */ }
  
! {xcstart}		{
  					xcdepth = 0;
  					BEGIN(xc);
  					/* Put back any characters past slash-star; see above */
--- 255,266 ----
   */
  
  %%
! {whitespace}	{ parseOffset += yyleng;
!                   /* ignore */
!                 }
  
! {xcstart}		{              
!                                         parseOffset += 2;
  					xcdepth = 0;
  					BEGIN(xc);
  					/* Put back any characters past slash-star; see above */
*************** other			.
*** 264,293 ****
  				}
  
  <xc>{xcstart}	{
  					xcdepth++;
  					/* Put back any characters past slash-star; see above */
  					yyless(2);
  				}
  
  <xc>{xcstop}	{
  					if (xcdepth <= 0)
  						BEGIN(INITIAL);
  					else
  						xcdepth--;
  				}
  
! <xc>{xcinside}	{ /* ignore */ }
  
! <xc>{op_chars}	{ /* ignore */ }
  
  <xc><<EOF>>		{ elog(ERROR, "Unterminated /* comment"); }
  
! {xbitstart}		{
  					BEGIN(xbit);
  					startlit();
  					addlit("b", 1);
  				}
  <xbit>{xbitstop}	{
  					BEGIN(INITIAL);
  					if (literalbuf[strspn(literalbuf + 1, "01") + 1] != '\0')
  						elog(ERROR, "invalid bit string input: '%s'",
--- 268,303 ----
  				}
  
  <xc>{xcstart}	{
+                                         parseOffset += 2;
  					xcdepth++;
  					/* Put back any characters past slash-star; see above */
  					yyless(2);
  				}
  
  <xc>{xcstop}	{
+                                         parseOffset += yyleng;
  					if (xcdepth <= 0)
  						BEGIN(INITIAL);
  					else
  						xcdepth--;
  				}
  
! <xc>{xcinside}	{ parseOffset += yyleng;
!                   /* ignore */ }
  
! <xc>{op_chars}	{ parseOffset += yyleng;
!                   /* ignore */ }
  
  <xc><<EOF>>		{ elog(ERROR, "Unterminated /* comment"); }
  
! {xbitstart}		{               
!                                         parseOffset += yyleng;
  					BEGIN(xbit);
  					startlit();
  					addlit("b", 1);
  				}
  <xbit>{xbitstop}	{
+                                         parseOffset += yyleng;
  					BEGIN(INITIAL);
  					if (literalbuf[strspn(literalbuf + 1, "01") + 1] != '\0')
  						elog(ERROR, "invalid bit string input: '%s'",
*************** other			.
*** 297,311 ****
  				}
  <xh>{xhinside}	|
  <xbit>{xbitinside}	{
  					addlit(yytext, yyleng);
  				}
  <xh>{xhcat}		|
! <xbit>{xbitcat}		{
  					/* ignore */
  				}
  <xbit><<EOF>>		{ elog(ERROR, "unterminated bit string literal"); }
  
  {xhstart}		{
  					BEGIN(xh);
  					startlit();
  				}
--- 307,324 ----
  				}
  <xh>{xhinside}	|
  <xbit>{xbitinside}	{
+                                         parseOffset += yyleng;
  					addlit(yytext, yyleng);
  				}
  <xh>{xhcat}		|
! <xbit>{xbitcat}		{  
!                                         parseOffset += yyleng;
  					/* ignore */
  				}
  <xbit><<EOF>>		{ elog(ERROR, "unterminated bit string literal"); }
  
  {xhstart}		{
+                                         parseOffset += yyleng;
  					BEGIN(xh);
  					startlit();
  				}
*************** other			.
*** 313,318 ****
--- 326,332 ----
  					long val;
  					char* endptr;
  
+                                         parseOffset += yyleng;
  					BEGIN(INITIAL);
  					errno = 0;
  					val = strtol(literalbuf, &endptr, 16);
*************** other			.
*** 330,339 ****
--- 344,355 ----
  <xh><<EOF>>		{ elog(ERROR, "Unterminated hexadecimal integer"); }
  
  {xqstart}		{
+                                         parseOffset += yyleng;
  					BEGIN(xq);
  					startlit();
  				}
  <xq>{xqstop}	{
+                                         parseOffset += yyleng;
  					BEGIN(INITIAL);
  					yylval.str = scanstr(literalbuf);
  					return SCONST;
*************** other			.
*** 341,359 ****
--- 357,379 ----
  <xq>{xqdouble}	|
  <xq>{xqinside}	|
  <xq>{xqliteral} {
+                                         parseOffset += yyleng;
  					addlit(yytext, yyleng);
  				}
  <xq>{xqcat}		{
+                                         parseOffset += yyleng;
  					/* ignore */
  				}
  <xq><<EOF>>		{ elog(ERROR, "Unterminated quoted string"); }
  
  
  {xdstart}		{
+                                         parseOffset += yyleng;
  					BEGIN(xd);
  					startlit();
  				}
  <xd>{xdstop}	{
+                                         parseOffset += yyleng;
  					BEGIN(INITIAL);
  					if (strlen(literalbuf) == 0)
  						elog(ERROR, "zero-length delimited identifier");
*************** other			.
*** 375,391 ****
  					return IDENT;
  				}
  <xd>{xddouble} {
  					addlit(yytext, yyleng-1);
  				}
! <xd>{xdinside}	{
  					addlit(yytext, yyleng);
  				}
  <xd><<EOF>>		{ elog(ERROR, "Unterminated quoted identifier"); }
  
! {typecast}		{ return TYPECAST; }
  
- {self}			{ return yytext[0]; }
- 
  {operator}		{
  					/*
  					 * Check for embedded slash-star or dash-dash; those
--- 395,417 ----
  					return IDENT;
  				}
  <xd>{xddouble} {
+                                         parseOffset += yyleng;
  					addlit(yytext, yyleng-1);
  				}
! <xd>{xdinside}	{                  
!                                         parseOffset += yyleng;
  					addlit(yytext, yyleng);
  				}
  <xd><<EOF>>		{ elog(ERROR, "Unterminated quoted identifier"); }
  
! {typecast}		{ 
!                           parseOffset += yyleng;
!                           return TYPECAST; }
! 
! {self}			{                                         
!                           parseOffset += yyleng;
!                           return yytext[0]; }
  
  {operator}		{
  					/*
  					 * Check for embedded slash-star or dash-dash; those
*************** other			.
*** 396,401 ****
--- 422,429 ----
  					int		nchars = yyleng;
  					char   *slashstar = strstr((char*)yytext, "/*");
  					char   *dashdash = strstr((char*)yytext, "--");
+ 					                                        
+                                         parseOffset += yyleng;
  
  					if (slashstar && dashdash)
  					{
*************** other			.
*** 455,461 ****
  					return Op;
  				}
  
! {param}			{
  					yylval.ival = atol((char*)&yytext[1]);
  					return PARAM;
  				}
--- 483,490 ----
  					return Op;
  				}
  
! {param}		
{                                                                                
!                                         parseOffset += yyleng;
  					yylval.ival = atol((char*)&yytext[1]);
  					return PARAM;
  				}
*************** other			.
*** 463,469 ****
  {integer}		{
  					long val;
  					char* endptr;
! 
  					errno = 0;
  					val = strtol((char *)yytext, &endptr, 10);
  					if (*endptr != '\0' || errno == ERANGE
--- 492,499 ----
  {integer}		{
  					long val;
  					char* endptr;
!                                                                                 
!                                         parseOffset += yyleng;
  					errno = 0;
  					val = strtol((char *)yytext, &endptr, 10);
  					if (*endptr != '\0' || errno == ERANGE
*************** other			.
*** 480,490 ****
  					yylval.ival = val;
  					return ICONST;
  				}
! {decimal}		{
  					yylval.str = pstrdup((char*)yytext);
  					return FCONST;
  				}
! {real}			{
  					yylval.str = pstrdup((char*)yytext);
  					return FCONST;
  				}
--- 510,522 ----
  					yylval.ival = val;
  					return ICONST;
  				}
! {decimal}	
{                                                                                
!                                         parseOffset += yyleng;
  					yylval.str = pstrdup((char*)yytext);
  					return FCONST;
  				}
! {real}		
{                                                                                
!                                         parseOffset += yyleng;
  					yylval.str = pstrdup((char*)yytext);
  					return FCONST;
  				}
*************** other			.
*** 493,498 ****
--- 525,532 ----
  {identifier}	{
  					ScanKeyword	   *keyword;
  					int				i;
+ 					                                        
+ 					parseOffset += yyleng;
  
  					/* Is it a keyword? */
  					keyword = ScanKeywordLookup((char*) yytext);
*************** other			.
*** 530,545 ****
  					return IDENT;
  				}
  
! {other}			{ return yytext[0]; }
  
  %%
  
  void
  yyerror(const char *message)
  {
! 	elog(ERROR, "parser: %s at or near \"%s\"", message, yytext);
  }
  
  int
  yywrap(void)
  {
--- 564,634 ----
  					return IDENT;
  				}
  
! {other}			{                                         
!                           parseOffset += yyleng;
!                           return yytext[0]; 
!                         }
  
  %%
  
  void
  yyerror(const char *message)
  {
!   int errorOffset;
!   char *line;
!   char *endOfLine;
!   char *beginningOfLine; 
!   size_t buffSize;
! 
!   /* Calculate the error's offset from the beginning of the input */
! 
!   errorOffset = parseOffset + 1 - yyleng;
! 
!   /* Find the beginning of the input line */
! 
!   for(beginningOfLine = parseString + errorOffset;
!       beginningOfLine > parseString;
!       beginningOfLine--)
!     if(*(beginningOfLine - 1) == '\n' || 
!        *(beginningOfLine - 1) == '\r' ||
!        *(beginningOfLine - 1) == '\f')
!       break;
! 
!   /* Find the end of the input line */
! 
!   for(endOfLine = parseString + errorOffset;
!       *endOfLine != '\0';
!       endOfLine++)
!     if(*endOfLine == '\n' ||
!        *endOfLine == '\r' ||
!        *endOfLine == '\f')
!       break;
! 
!   /* Calculate the offset of the error into the input line */
! 
!   errorOffset = errorOffset - (int)(beginningOfLine - parseString);
! 
!   /* Allocate a buffer for the line */
! 
!   buffSize = (endOfLine - beginningOfLine) + 1;
!   line = palloc(buffSize);
! 
!   /* Copy the line into the buffer */
! 
!   memcpy(line, beginningOfLine, buffSize);
!   *(line + buffSize - 1) = '\0';
! 
!   /* Report the error */
! 
!   elog(ERROR, "parser: %s at or near \"%s\":\n%s\n%*s", 
!        message, 
!        yytext,
!        line, 
!        errorOffset, 
!        "^");
  }
  
+ 
  int
  yywrap(void)
  {
*************** scanner_init(void)
*** 557,562 ****
--- 646,655 ----
  	   because input()/myinput() checks the non-nullness of parseCh
  	   to know when to pass the string to lex/flex */
  	parseCh = NULL;
+ 
+ 	/* Initialize the parse input offset -- used by enhanced syntax error
reporting */
+ 
+ 	parseOffset = 0;
  
  	/* initialize literal buffer to a reasonable but expansible size */
  	literalalloc = 128;
Index: src/test/regress/expected/errors.out
===================================================================
RCS file:
/home/projects/pgsql/cvsroot/pgsql/src/test/regress/expected/errors.out,v
retrieving revision 1.26
diff -c -p -r1.26 errors.out
*** src/test/regress/expected/errors.out	2000/11/08 22:10:03	1.26
--- src/test/regress/expected/errors.out	2001/08/01 17:43:56
*************** select 1
*** 19,25 ****
  select
  -- no such relation 
  select * from nonesuch;
! ERROR:  parser: parse error at or near "select"
  -- bad name in target list
  select nonesuch from pg_database;
  ERROR:  Attribute 'nonesuch' not found
--- 19,27 ----
  select
  -- no such relation 
  select * from nonesuch;
! ERROR:  parser: parse error at or near "select":
! select
! ^
  -- bad name in target list
  select nonesuch from pg_database;
  ERROR:  Attribute 'nonesuch' not found
*************** select * from pg_database where pg_datab
*** 31,37 ****
  ERROR:  Attribute 'nonesuch' not found
  -- bad select distinct on syntax, distinct attribute missing
  select distinct on (foobar) from pg_database;
! ERROR:  parser: parse error at or near "from"
  -- bad select distinct on syntax, distinct attribute not in target
list
  select distinct on (foobar) * from pg_database;
  ERROR:  Attribute 'foobar' not found
--- 33,41 ----
  ERROR:  Attribute 'nonesuch' not found
  -- bad select distinct on syntax, distinct attribute missing
  select distinct on (foobar) from pg_database;
! ERROR:  parser: parse error at or near "from":
! select distinct on (foobar) from pg_database;
!                             ^
  -- bad select distinct on syntax, distinct attribute not in target
list
  select distinct on (foobar) * from pg_database;
  ERROR:  Attribute 'foobar' not found
*************** ERROR:  Attribute 'foobar' not found
*** 39,46 ****
  -- DELETE
   
  -- missing relation name (this had better not wildcard!) 
  delete from;
! ERROR:  parser: parse error at or near ";"
  -- no such relation 
  delete from nonesuch;
  ERROR:  Relation 'nonesuch' does not exist
--- 43,52 ----
  -- DELETE
   
  -- missing relation name (this had better not wildcard!) 
+ delete from;
+ ERROR:  parser: parse error at or near ";":
  delete from;
!            ^
  -- no such relation 
  delete from nonesuch;
  ERROR:  Relation 'nonesuch' does not exist
*************** ERROR:  Relation 'nonesuch' does not exi
*** 49,55 ****
   
  -- missing relation name (this had better not wildcard!) 
  drop table;
! ERROR:  parser: parse error at or near ";"
  -- no such relation 
  drop table nonesuch;
  ERROR:  table "nonesuch" does not exist
--- 55,63 ----
   
  -- missing relation name (this had better not wildcard!) 
  drop table;
! ERROR:  parser: parse error at or near ";":
! drop table;
!           ^
  -- no such relation 
  drop table nonesuch;
  ERROR:  table "nonesuch" does not exist
*************** ERROR:  table "nonesuch" does not exist
*** 58,65 ****
   
  -- relation renaming 
  -- missing relation name 
  alter table rename;
! ERROR:  parser: parse error at or near ";"
  -- no such relation 
  alter table nonesuch rename to newnonesuch;
  ERROR:  Relation "nonesuch" does not exist
--- 66,75 ----
   
  -- relation renaming 
  -- missing relation name 
+ alter table rename;
+ ERROR:  parser: parse error at or near ";":
  alter table rename;
!                   ^
  -- no such relation 
  alter table nonesuch rename to newnonesuch;
  ERROR:  Relation "nonesuch" does not exist
*************** ERROR:  Define: "basetype" unspecified
*** 116,125 ****
   
  -- missing index name 
  drop index;
! ERROR:  parser: parse error at or near ";"
  -- bad index name 
  drop index 314159;
! ERROR:  parser: parse error at or near "314159"
  -- no such index 
  drop index nonesuch;
  ERROR:  index "nonesuch" does not exist
--- 126,139 ----
   
  -- missing index name 
  drop index;
! ERROR:  parser: parse error at or near ";":
! drop index;
!           ^
  -- bad index name 
+ drop index 314159;
+ ERROR:  parser: parse error at or near "314159":
  drop index 314159;
!            ^
  -- no such index 
  drop index nonesuch;
  ERROR:  index "nonesuch" does not exist
*************** ERROR:  index "nonesuch" does not exist
*** 127,143 ****
  -- REMOVE AGGREGATE
   
  -- missing aggregate name 
  drop aggregate;
! ERROR:  parser: parse error at or near ";"
  -- bad aggregate name 
  drop aggregate 314159;
! ERROR:  parser: parse error at or near "314159"
  -- no such aggregate 
  drop aggregate nonesuch;
! ERROR:  parser: parse error at or near ";"
  -- missing aggregate type
  drop aggregate newcnt1;
! ERROR:  parser: parse error at or near ";"
  -- bad aggregate type
  drop aggregate newcnt nonesuch;
  ERROR:  RemoveAggregate: type 'nonesuch' does not exist
--- 141,165 ----
  -- REMOVE AGGREGATE
   
  -- missing aggregate name 
+ drop aggregate;
+ ERROR:  parser: parse error at or near ";":
  drop aggregate;
!               ^
  -- bad aggregate name 
  drop aggregate 314159;
! ERROR:  parser: parse error at or near "314159":
! drop aggregate 314159;
!                      ^
  -- no such aggregate 
+ drop aggregate nonesuch;
+ ERROR:  parser: parse error at or near ";":
  drop aggregate nonesuch;
!                        ^
  -- missing aggregate type
  drop aggregate newcnt1;
! ERROR:  parser: parse error at or near ";":
! drop aggregate newcnt1;
!                       ^
  -- bad aggregate type
  drop aggregate newcnt nonesuch;
  ERROR:  RemoveAggregate: type 'nonesuch' does not exist
*************** ERROR:  RemoveAggregate: aggregate 'newc
*** 148,158 ****
  -- REMOVE FUNCTION
   
  -- missing function name 
  drop function ();
! ERROR:  parser: parse error at or near "("
  -- bad function name 
  drop function 314159();
! ERROR:  parser: parse error at or near "314159"
  -- no such function 
  drop function nonesuch();
  ERROR:  RemoveFunction: function 'nonesuch()' does not exist
--- 170,184 ----
  -- REMOVE FUNCTION
   
  -- missing function name 
+ drop function ();
+ ERROR:  parser: parse error at or near "(":
  drop function ();
!                 ^
  -- bad function name 
  drop function 314159();
! ERROR:  parser: parse error at or near "314159":
! drop function 314159();
!                       ^
  -- no such function 
  drop function nonesuch();
  ERROR:  RemoveFunction: function 'nonesuch()' does not exist
*************** ERROR:  RemoveFunction: function 'nonesu
*** 160,170 ****
  -- REMOVE TYPE
   
  -- missing type name 
  drop type;
! ERROR:  parser: parse error at or near ";"
  -- bad type name 
  drop type 314159;
! ERROR:  parser: parse error at or near "314159"
  -- no such type 
  drop type nonesuch;
  ERROR:  RemoveType: type 'nonesuch' does not exist
--- 186,200 ----
  -- REMOVE TYPE
   
  -- missing type name 
+ drop type;
+ ERROR:  parser: parse error at or near ";":
  drop type;
!          ^
  -- bad type name 
+ drop type 314159;
+ ERROR:  parser: parse error at or near "314159":
  drop type 314159;
!           ^
  -- no such type 
  drop type nonesuch;
  ERROR:  RemoveType: type 'nonesuch' does not exist
*************** ERROR:  RemoveType: type 'nonesuch' does
*** 173,194 ****
   
  -- missing everything 
  drop operator;
! ERROR:  parser: parse error at or near ";"
  -- bad operator name 
  drop operator equals;
! ERROR:  parser: parse error at or near "equals"
  -- missing type list 
  drop operator ===;
! ERROR:  parser: parse error at or near ";"
  -- missing parentheses 
  drop operator int4, int4;
! ERROR:  parser: parse error at or near "int4"
  -- missing operator name 
  drop operator (int4, int4);
! ERROR:  parser: parse error at or near "("
  -- missing type list contents 
  drop operator === ();
! ERROR:  parser: parse error at or near ")"
  -- no such operator 
  drop operator === (int4);
  ERROR:  parser: argument type missing (use NONE for unary operators)
--- 203,236 ----
   
  -- missing everything 
  drop operator;
! ERROR:  parser: parse error at or near ";":
! drop operator;
!              ^
  -- bad operator name 
+ drop operator equals;
+ ERROR:  parser: parse error at or near "equals":
  drop operator equals;
!               ^
  -- missing type list 
  drop operator ===;
! ERROR:  parser: parse error at or near ";":
! drop operator ===;
!                  ^
  -- missing parentheses 
+ drop operator int4, int4;
+ ERROR:  parser: parse error at or near "int4":
  drop operator int4, int4;
!                     ^
  -- missing operator name 
  drop operator (int4, int4);
! ERROR:  parser: parse error at or near "(":
! drop operator (int4, int4);
!               ^
  -- missing type list contents 
+ drop operator === ();
+ ERROR:  parser: parse error at or near ")":
  drop operator === ();
!                    ^
  -- no such operator 
  drop operator === (int4);
  ERROR:  parser: argument type missing (use NONE for unary operators)
*************** ERROR:  RemoveOperator: binary operator 
*** 199,206 ****
  drop operator = (nonesuch);
  ERROR:  parser: argument type missing (use NONE for unary operators)
  -- no such type1 
  drop operator = ( , int4);
! ERROR:  parser: parse error at or near ","
  -- no such type1 
  drop operator = (nonesuch, int4);
  ERROR:  RemoveOperator: type 'nonesuch' does not exist
--- 241,250 ----
  drop operator = (nonesuch);
  ERROR:  parser: argument type missing (use NONE for unary operators)
  -- no such type1 
+ drop operator = ( , int4);
+ ERROR:  parser: parse error at or near ",":
  drop operator = ( , int4);
!                   ^
  -- no such type1 
  drop operator = (nonesuch, int4);
  ERROR:  RemoveOperator: type 'nonesuch' does not exist
*************** drop operator = (int4, nonesuch);
*** 209,233 ****
  ERROR:  RemoveOperator: type 'nonesuch' does not exist
  -- no such type2 
  drop operator = (int4, );
! ERROR:  parser: parse error at or near ")"
  --
  -- DROP RULE
   
  -- missing rule name 
  drop rule;
! ERROR:  parser: parse error at or near ";"
  -- bad rule name 
  drop rule 314159;
! ERROR:  parser: parse error at or near "314159"
  -- no such rule 
  drop rule nonesuch;
  ERROR:  Rule or view "nonesuch" not found
  -- bad keyword 
  drop tuple rule nonesuch;
! ERROR:  parser: parse error at or near "tuple"
  -- no such rule 
  drop instance rule nonesuch;
! ERROR:  parser: parse error at or near "instance"
  -- no such rule 
  drop rewrite rule nonesuch;
! ERROR:  parser: parse error at or near "rewrite"
--- 253,289 ----
  ERROR:  RemoveOperator: type 'nonesuch' does not exist
  -- no such type2 
  drop operator = (int4, );
! ERROR:  parser: parse error at or near ")":
! drop operator = (int4, );
!                        ^
  --
  -- DROP RULE
   
  -- missing rule name 
+ drop rule;
+ ERROR:  parser: parse error at or near ";":
  drop rule;
!          ^
  -- bad rule name 
+ drop rule 314159;
+ ERROR:  parser: parse error at or near "314159":
  drop rule 314159;
!           ^
  -- no such rule 
  drop rule nonesuch;
  ERROR:  Rule or view "nonesuch" not found
  -- bad keyword 
  drop tuple rule nonesuch;
! ERROR:  parser: parse error at or near "tuple":
! drop tuple rule nonesuch;
!      ^
  -- no such rule 
+ drop instance rule nonesuch;
+ ERROR:  parser: parse error at or near "instance":
  drop instance rule nonesuch;
!      ^
  -- no such rule 
+ drop rewrite rule nonesuch;
+ ERROR:  parser: parse error at or near "rewrite":
  drop rewrite rule nonesuch;
!      ^
\ No newline at end of file
Index: src/test/regress/expected/strings.out
===================================================================
RCS file:
/home/projects/pgsql/cvsroot/pgsql/src/test/regress/expected/strings.out,v
retrieving revision 1.10
diff -c -p -r1.10 strings.out
*** src/test/regress/expected/strings.out	2001/06/01 17:49:17	1.10
--- src/test/regress/expected/strings.out	2001/08/01 17:43:56
*************** SELECT 'first line'
*** 17,23 ****
  ' - next line' /* this comment is not allowed here */
  ' - third line'
  	AS "Illegal comment within continuation";
! ERROR:  parser: parse error at or near "'"
  --
  -- test conversions between various string types
  --
--- 17,25 ----
  ' - next line' /* this comment is not allowed here */
  ' - third line'
  	AS "Illegal comment within continuation";
! ERROR:  parser: parse error at or near "'":
! ' - third line'
!               ^
  --
  -- test conversions between various string types
  --
Index: src/test/regress/output/constraints.source
===================================================================
RCS file:
/home/projects/pgsql/cvsroot/pgsql/src/test/regress/output/constraints.source,v
retrieving revision 1.18
diff -c -p -r1.18 constraints.source
*** src/test/regress/output/constraints.source	2001/02/22 05:32:56	1.18
--- src/test/regress/output/constraints.source	2001/08/01 17:43:56
*************** SELECT '' AS four, * FROM DEFAULTEXPR_TB
*** 45,56 ****
  -- syntax errors
  --  test for extraneous comma
  CREATE TABLE error_tbl (i int DEFAULT (100, ));
! ERROR:  parser: parse error at or near ","
  --  this will fail because gram.y uses b_expr not a_expr for defaults,
  --  to avoid a shift/reduce conflict that arises from NOT NULL being
  --  part of the column definition syntax:
  CREATE TABLE error_tbl (b1 bool DEFAULT 1 IN (1, 2));
! ERROR:  parser: parse error at or near "IN"
  --  this should work, however:
  CREATE TABLE error_tbl (b1 bool DEFAULT (1 IN (1, 2)));
  DROP TABLE error_tbl;
--- 45,60 ----
  -- syntax errors
  --  test for extraneous comma
  CREATE TABLE error_tbl (i int DEFAULT (100, ));
! ERROR:  parser: parse error at or near ",":
! CREATE TABLE error_tbl (i int DEFAULT (100, ));
!                                           ^
  --  this will fail because gram.y uses b_expr not a_expr for defaults,
  --  to avoid a shift/reduce conflict that arises from NOT NULL being
  --  part of the column definition syntax:
  CREATE TABLE error_tbl (b1 bool DEFAULT 1 IN (1, 2));
! ERROR:  parser: parse error at or near "IN":
! CREATE TABLE error_tbl (b1 bool DEFAULT 1 IN (1, 2));
!                                           ^
  --  this should work, however:
  CREATE TABLE error_tbl (b1 bool DEFAULT (1 IN (1, 2)));
  DROP TABLE error_tbl;

Wed, 01 Aug 2001 13:58:45 -0400
Neil Padgett <npadgett@redhat.com>
Patch for Improved Syntax Error Reporting
Neil Padgett <npadgett@redhat.com> writes:
> Attached please find a patch to the input parser that yields better
> syntax error reporting on parse errors.

This has been discussed before (you guys really should spend more time
reading the mail list archives) and in fact you are not the first to
submit essentially this patch.  The major objections to reporting syntax
problems this way, IIRC, are that (a) it makes unsupportable assumptions
about what the user interface looks like, for example the assumption
that the error message will be displayed in a fixed-width font; and
(b) it becomes essentially useless when the input query exceeds a few
lines in size.

The conclusion we had come to in previous discussion is that the error
offset ought to be delivered to the client application as a separate
component of the error report, and the client ought to be responsible
for doing something appropriate with it --- which might, for example,
include highlighting the offending word(s) if it's a GUI application
that has the input query in a window.  psql couldn't do that, but might
choose to redisplay a few dozen characters around the position of the
error.

In any case, the limiting factor is not the parser change, which is
trivial, but our ability/willingness to change the on-the-wire protocol
to allow error reports to contain multiple components.  There are some
other useful things that could be done once we did that.  Again, I'd
recommend trawling the archives for a bit.

			regards, tom lane

Wed, 01 Aug 2001 14:33:13 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: Patch for Improved Syntax Error Reporting 
Tom Lane wrote:
> 
> Neil Padgett <npadgett@redhat.com> writes:
> > Attached please find a patch to the input parser that yields better
> > syntax error reporting on parse errors.
> 
> This has been discussed before (you guys really should spend more time
> reading the mail list archives) and in fact you are not the first to

I've just read the relevant messages. Though, I do find the list
archives a bit slow for any useful browsing -- can I grab a copy of them
from somewhere? Setting up a mirror might be an idea. . .

> submit essentially this patch.  The major objections to reporting syntax
> problems this way, IIRC, are that (a) it makes unsupportable assumptions
> about what the user interface looks like, for example the assumption
> that the error message will be displayed in a fixed-width font; and

Can you cite a client which does not use a fixed-width font at this
time? I think most I've worked with use one for SQL interaction -- it is
pretty much "the way things are done." I suppose, however, there could
be some clients which display error messages in a dialog box or
something similar, so I do agree that this is something that does need
to be handled, and which the patch doesn't address. See below for a
suggestion for this.

> (b) it becomes essentially useless when the input query exceeds a few
> lines in size.

How so? I grab out the line of interest when reporting the error.

> 
> The conclusion we had come to in previous discussion is that the error
> offset ought to be delivered to the client application as a separate
> component of the error report, and the client ought to be responsible
> for doing something appropriate with it --- which might, for example,
> include highlighting the offending word(s) if it's a GUI application
> that has the input query in a window.  psql couldn't do that, but might
> choose to redisplay a few dozen characters around the position of the
> error.

Well, perhaps the error message could be changed to something like this,
with a special string marking the parse error position?

test=# SELECT * FRUM bob;
ERROR:  parser: parse error at or near 'frum':
SELECT * ***FRUM bob;

Or, perhaps better than a magic string:

test=# SELECT * FRUM bob;
ERROR:  parser: parse error at or near 'frum' (index 10)
         
The latter is probably more useful, though it does place a burden on the
client to format and display an error message. But, the client program
can mark out the error in any way it sees fit. In fact, it could even
leave the raw message in place and still the user will get something
more useful than the current output. No protocol change is required, but
very useful functionality is added.

Neil

-- 
Neil Padgett
Red Hat Canada Ltd.                       E-Mail:  npadgett@redhat.com
2323 Yonge Street, Suite #300, 
Toronto, ON  M4P 2C9

Wed, 01 Aug 2001 14:56:37 -0400
Neil Padgett <npadgett@redhat.com>
Re: Patch for Improved Syntax Error Reporting
> Tom Lane wrote:
> > 
> > Neil Padgett <npadgett@redhat.com> writes:
> > > Attached please find a patch to the input parser that yields better
> > > syntax error reporting on parse errors.
> > 
> > This has been discussed before (you guys really should spend more time
> > reading the mail list archives) and in fact you are not the first to

Tom, it is hard to imagine how they would even find relevant stuff on
this issue.  The TODO.detail item is very vague.  Would they start
searching for keywords in the mailing list search engine?  Not sure what
keywords they would even use.

In fact, their solution is an improvement over what is in
TODO.detail/yacc now.

> I've just read the relevant messages. Though, I do find the list
> archives a bit slow for any useful browsing -- can I grab a copy of them
> from somewhere? Setting up a mirror might be an idea. . .

The whole internet seems slow today.  I think it is that Code Red worm.

> > submit essentially this patch.  The major objections to reporting syntax
> > problems this way, IIRC, are that (a) it makes unsupportable assumptions
> > about what the user interface looks like, for example the assumption
> > that the error message will be displayed in a fixed-width font; and
> 
> Can you cite a client which does not use a fixed-width font at this
> time? I think most I've worked with use one for SQL interaction -- it is
> pretty much "the way things are done." I suppose, however, there could
> be some clients which display error messages in a dialog box or
> something similar, so I do agree that this is something that does need
> to be handled, and which the patch doesn't address. See below for a
> suggestion for this.

I know some people like a client-independent way of displaying errors,
but I like the direct approach of this patch, returning a string with
the error line highlighted and the location marked.  I don't want to
push added complexity into the client, especially when we don't even
have a client who has this need yet.

IMHO, I am starting to see a lot of over-engineering demands made of
these patches.  I think it is wasting time and is of little value to
average PostgreSQL users.  Of course, others may disagree, but that is
my opinion.

So, my vote is to accept the patch as-is.  When we have need for more
complex reporting, we can add it.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Wed, 1 Aug 2001 15:24:15 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Patch for Improved Syntax Error Reporting
Neil Padgett <npadgett@redhat.com> writes:
> I've just read the relevant messages. Though, I do find the list
> archives a bit slow for any useful browsing -- can I grab a copy of them
> from somewhere? Setting up a mirror might be an idea. . .

The raw archives are under http://www.ca.postgresql.org/mhonarc/
in monthly files, for example
http://www.ca.postgresql.org/mhonarc/pgsql-patches/archive/pgsql-patches.200108

I am not sure whether our mirror sites mirror them or not.  In any case,
you should talk to Marc if you want to coordinate some sort of long-term
mirroring arrangement.

> Can you cite a client which does not use a fixed-width font at this
> time? I think most I've worked with use one for SQL interaction -- it is
> pretty much "the way things are done."

I'd believe that data is entered/displayed in fixed-width text; I'm less
ready to assume that for error messages, however.

>> (b) it becomes essentially useless when the input query exceeds a few
>> lines in size.

> How so? I grab out the line of interest when reporting the error.

My apologies, I missed that aspect of your patch.  An interesting
solution.  However, it doesn't handle embedded tabs, and there is still
the objection that a client app might want to present the location info
in a completely different fashion anyway.

>> The conclusion we had come to in previous discussion is that the error
>> offset ought to be delivered to the client application as a separate
>> component of the error report,

> Well, perhaps the error message could be changed to something like this,
> with a special string marking the parse error position?

> test=# SELECT * FRUM bob;
> ERROR:  parser: parse error at or near 'frum':
> SELECT * ***FRUM bob;

I was thinking something along the lines of

	ERROR: message string just like now
	POSITION: 42
	OTHERSTUFF: yadda yadda

ie, the error message string is now interpreted as keyworded lines,
somewhat like (say) mail headers.  This would be workable for new
clients, wouldn't break anything at the wire-protocol level, and would
not be totally useless if presented "raw" to a user by an old client.
See the archives for more info --- I think the last discussion was three
or four months back when Peter E. started to make noises about fixing
elog for internationalization.

			regards, tom lane

Wed, 01 Aug 2001 15:37:32 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: Patch for Improved Syntax Error Reporting 
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Tom, it is hard to imagine how they would even find relevant stuff on
> this issue.  The TODO.detail item is very vague.

I dunno that it's vague --- a quick look indicates that TODO.detail/elog
has most of the recent messages on the subject.  (Neil, the "recent
discussion" that I referred to seems to be in there, or most of it
anyway, if you didn't see it in the archives yet.)

> In fact, their solution is an improvement over what is in
> TODO.detail/yacc now.

Agreed, the idea of pulling out just the one line is an improvement over
the last patch.  It's still going down the wrong path though.  We should
be empowering client apps to highlight syntax errors properly, not
presenting edited info in a way that might be useful to humans but will
be unintelligible to programs.  If we go that route, it will be harder
to do the right thing later.

> I know some people like a client-independent way of displaying errors,
> but I like the direct approach of this patch, returning a string with
> the error line highlighted and the location marked.  I don't want to
> push added complexity into the client, especially when we don't even
> have a client who has this need yet.

pgAdmin, phpAdmin, pgaccess, and friends don't count?  We have GUI front
ends *today*, you know.

			regards, tom lane

Wed, 01 Aug 2001 15:50:23 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: Patch for Improved Syntax Error Reporting 
> > In fact, their solution is an improvement over what is in
> > TODO.detail/yacc now.
> 
> Agreed, the idea of pulling out just the one line is an improvement over
> the last patch.  It's still going down the wrong path though.  We should
> be empowering client apps to highlight syntax errors properly, not
> presenting edited info in a way that might be useful to humans but will
> be unintelligible to programs.  If we go that route, it will be harder
> to do the right thing later.
> 
> > I know some people like a client-independent way of displaying errors,
> > but I like the direct approach of this patch, returning a string with
> > the error line highlighted and the location marked.  I don't want to
> > push added complexity into the client, especially when we don't even
> > have a client who has this need yet.
> 
> pgAdmin, phpAdmin, pgaccess, and friends don't count?  We have GUI front
> ends *today*, you know.

But how do they display error messages now?  Can't they just continue
doing that with this new code?  Do we want to make them code their own
error handling, and for what little benefit?  Let them figure out how to
display the error in fixed-width font and be done with it.  I am sure
they have bigger things to do than colorize error locations.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Wed, 1 Aug 2001 16:10:05 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Patch for Improved Syntax Error Reporting
> > > In fact, their solution is an improvement over what is in
> > > TODO.detail/yacc now.
> > 
> > Agreed, the idea of pulling out just the one line is an improvement over
> > the last patch.  It's still going down the wrong path though.  We should
> > be empowering client apps to highlight syntax errors properly, not
> > presenting edited info in a way that might be useful to humans but will
> > be unintelligible to programs.  If we go that route, it will be harder
> > to do the right thing later.
> > 
> > > I know some people like a client-independent way of displaying errors,
> > > but I like the direct approach of this patch, returning a string with
> > > the error line highlighted and the location marked.  I don't want to
> > > push added complexity into the client, especially when we don't even
> > > have a client who has this need yet.
> > 
> > pgAdmin, phpAdmin, pgaccess, and friends don't count?  We have GUI front
> > ends *today*, you know.
> 
> But how do they display error messages now?  Can't they just continue
> doing that with this new code?  Do we want to make them code their own
> error handling, and for what little benefit?  Let them figure out how to
> display the error in fixed-width font and be done with it.  I am sure
> they have bigger things to do than colorize error locations.

A bigger question is that if we decide to output just offset information
in the message, we have to be sure _all_ the clients can interpret it or
the syntax information is confusing.  Are we prepared to get all the
clients update at the same time we add the feature?  Seems we should go
with a simple solution now and add later.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Wed, 1 Aug 2001 17:23:11 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Patch for Improved Syntax Error Reporting
Bruce Momjian wrote:
> 
> > > > In fact, their solution is an improvement over what is in
> > > > TODO.detail/yacc now.
> > >
> > > Agreed, the idea of pulling out just the one line is an improvement over
> > > the last patch.  It's still going down the wrong path though.  We should
> > > be empowering client apps to highlight syntax errors properly, not
> > > presenting edited info in a way that might be useful to humans but will
> > > be unintelligible to programs.  If we go that route, it will be harder
> > > to do the right thing later.
> > >
> > > > I know some people like a client-independent way of displaying errors,
> > > > but I like the direct approach of this patch, returning a string with
> > > > the error line highlighted and the location marked.  I don't want to
> > > > push added complexity into the client, especially when we don't even
> > > > have a client who has this need yet.
> > >
> > > pgAdmin, phpAdmin, pgaccess, and friends don't count?  We have GUI front
> > > ends *today*, you know.
> >
> > But how do they display error messages now?  Can't they just continue
> > doing that with this new code?  Do we want to make them code their own
> > error handling, and for what little benefit?  Let them figure out how to
> > display the error in fixed-width font and be done with it.  I am sure
> > they have bigger things to do than colorize error locations.
> 
> A bigger question is that if we decide to output just offset information
> in the message, we have to be sure _all_ the clients can interpret it or
> the syntax information is confusing.  Are we prepared to get all the
> clients update at the same time we add the feature?  Seems we should go
> with a simple solution now and add later.
> 

If instead of printing:

ERROR: A parse error near "foo"

we print

ERROR: A parse error near "foo" (index=10)

it should not affect any of the existing clients.
For the clients, this will be just text as before and they will print it as
received.  If some client wants, it may look for the index information and do
whatever is convenient for that interface (as an enhancement).

So I think this option is backward compatible.

-- 
Fernando Nasser
Red Hat - Toronto                       E-Mail:  fnasser@redhat.com
2323 Yonge Street, Suite #300
Toronto, Ontario   M4P 2C9

Wed, 01 Aug 2001 17:34:22 -0400
Fernando Nasser <fnasser@cygnus.com>
Re: Patch for Improved Syntax Error Reporting
Fernando Nasser <fnasser@cygnus.com> writes:
> If instead of printing:
> ERROR: A parse error near "foo"
> we print
> ERROR: A parse error near "foo" (index=10)
> it should not affect any of the existing clients.

One objection to this idea is that it doesn't play nicely with
localization of error message texts.  I'd sooner do

	ERROR: A parse error near "foo"
	ERRORLOCATION: 10

which doesn't create any problems with localization (there's no
particular need to translate the keywords, since a client probably
wouldn't show them to the user anyway).  It's just as backward
compatible, and not that much uglier for an old client.

			regards, tom lane

Wed, 01 Aug 2001 18:22:00 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: Patch for Improved Syntax Error Reporting 
Tom Lane wrote:
> 
> Fernando Nasser <fnasser@cygnus.com> writes:
> > If instead of printing:
> > ERROR: A parse error near "foo"
> > we print
> > ERROR: A parse error near "foo" (index=10)
> > it should not affect any of the existing clients.
> 
> One objection to this idea is that it doesn't play nicely with
> localization of error message texts.  I'd sooner do
> 
>         ERROR: A parse error near "foo"
>         ERRORLOCATION: 10
> 
> which doesn't create any problems with localization (there's no
> particular need to translate the keywords, since a client probably
> wouldn't show them to the user anyway).  It's just as backward
> compatible, and not that much uglier for an old client.

I'm not sure how this format causes a problem with localization. The
trailing bracketed text isn't part of the message text -- it's just a
set of fields and values. So, since the keywords aren't really intended
for raw display, they don't require translation. Parsing the format is
no harder, and the raw output isn't as ugly as is a multi-line list of
fields and values, IMHO. (I really dislike unnecessarily having gobs of
output lines in the message.)

Neil

-- 
Neil Padgett
Red Hat Canada Ltd.                       E-Mail:  npadgett@redhat.com
2323 Yonge Street, Suite #300, 
Toronto, ON  M4P 2C9

Wed, 01 Aug 2001 18:38:29 -0400
Neil Padgett <npadgett@redhat.com>
Re: Patch for Improved Syntax Error Reporting
Neil Padgett <npadgett@redhat.com> writes:
> I'm not sure how this format causes a problem with localization. The
> trailing bracketed text isn't part of the message text -- it's just a
> set of fields and values.

It *looks* like it is part of the message text --- to users, and to
programs that aren't specifically aware that it isn't.  A user-friendly
client would need to take extra steps to strip out the (index=N) part
to avoid complaints from users that their error messages aren't getting
fully translated.

> So, since the keywords aren't really intended
> for raw display, they don't require translation. Parsing the format is
> no harder, and the raw output isn't as ugly as is a multi-line list of
> fields and values, IMHO. (I really dislike unnecessarily having gobs of
> output lines in the message.)

I don't much care for it either, and wouldn't propose it if this were
the sole application.  However, we have other applications, as noted in
the previous discussion:

--- distinguishing the actual error message from tips/hints about what
    to do about it.  There are a fair number of these already, and right
    now there's just a very weak formatting convention that hints
    appear on a separate line.

--- distinguishing a translatable (primary) error message from a
    maintainer error message that need not be translated.  We have lots
    and lots of errors in the backend that could all fit under a single
    primary error code of "Internal error, please report this to
    pgsql-bugs", thus vastly reducing the burden on message translators.
    The maintainer error message (eg, "foobar: unexpected node type 124")
    still needs to appear, but it could be a secondary field.

--- including backend file name and line number of the elog call, for
    easier debugging and unambiguous identification of an error source.

--- severity level

--- doubtless other ideas will occur to us once we have the capability.

Given all these potential benefits, I'm willing to endure the downside
of slightly ugly-looking error reports in old clients.  They'll still
*work*, mind you, and indeed emit info that users might like to have.
To the extent that it's clutter, people will be motivated to update
their clients.  Doesn't seem like much of a downside.

			regards, tom lane

Wed, 01 Aug 2001 18:51:35 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: Patch for Improved Syntax Error Reporting 
Tom Lane wrote:
> 
> Neil Padgett <npadgett@redhat.com> writes:
> > I'm not sure how this format causes a problem with localization. The
> > trailing bracketed text isn't part of the message text -- it's just a
> > set of fields and values.
> 
> It *looks* like it is part of the message text --- to users, and to
> programs that aren't specifically aware that it isn't.  A user-friendly
> client would need to take extra steps to strip out the (index=N) part
> to avoid complaints from users that their error messages aren't getting
> fully translated.
> 

This is exactly what I want. If you don't have a new client, it looks
like a message with some funk on the end. If you have a new, friendly
client, it will strip out the field/value list at the end. Exactly the
same as the multi-line list, really. And the translation complaint is
equally applicable to either format.

> > So, since the keywords aren't really intended
> > for raw display, they don't require translation. Parsing the format is
> > no harder, and the raw output isn't as ugly as is a multi-line list of
> > fields and values, IMHO. (I really dislike unnecessarily having gobs of
> > output lines in the message.)
> 
> I don't much care for it either, and wouldn't propose it if this were
> the sole application.  However, we have other applications, as noted in
> the previous discussion:
> 
> --- distinguishing the actual error message from tips/hints about what
>     to do about it.  There are a fair number of these already, and right
>     now there's just a very weak formatting convention that hints
>     appear on a separate line.

I didn't know that such a convention exists already -- how would these
hints look under your proposed new format?

> 
> --- distinguishing a translatable (primary) error message from a
>     maintainer error message that need not be translated.  We have lots
>     and lots of errors in the backend that could all fit under a single
>     primary error code of "Internal error, please report this to
>     pgsql-bugs", thus vastly reducing the burden on message translators.
>     The maintainer error message (eg, "foobar: unexpected node type 124")
>     still needs to appear, but it could be a secondary field.
> 

Why aren't we using numerics to do this? I recall reading something (in
the archives?) about them before, but I don't recall the outcome. Is
anything like numerics being added to help with the localization
efforts? It would seem this is the best way to handle primary errors,
versus maintainer errors.

> --- including backend file name and line number of the elog call, for
>     easier debugging and unambiguous identification of an error source.
> 
> --- severity level
> 
> --- doubtless other ideas will occur to us once we have the capability.

Hmm... You could do any of these with either format, but I'm starting to
that with this many fields, any message in my suggested format is
probably going to wrap. So I'm pretty much sold on a multi-line format.
(It might even be less ugly for messages with lots of fields!) 

> 
> Given all these potential benefits, I'm willing to endure the downside
> of slightly ugly-looking error reports in old clients.  They'll still
> *work*, mind you, and indeed emit info that users might like to have.
> To the extent that it's clutter, people will be motivated to update
> their clients.  Doesn't seem like much of a downside.
>

No, I don't think so either. It seems that this new format makes sense.
Would the elog call be changed to support passing in a list of
arguments? Or are you proposing we just hard code the field name / value
lists into the messages? (a bad idea, IMHO) We should probably introduce
a new call, say, eelog (for enhanced error log) that takes such a list,
and then we could define elog as a macro which calls eelog with suitable
defaults for use with "legacy" messages. Then, we wouldn't need to go
after every error message right away. (And in fact, probably, in the
case of soem rare messages. need not ever.)

The question this brings up is whether a logging change can / should be
tackled in this release. Specifically, with the current state of
internationalization work, is it best to do it now, or later? Or, for
now, should we just decide on an output format, and then hardcode the
field output for just the syntax error reporting, leaving everything
else to be tackled later?

Neil

-- 
Neil Padgett
Red Hat Canada Ltd.                       E-Mail:  npadgett@redhat.com
2323 Yonge Street, Suite #300, 
Toronto, ON  M4P 2C9

Wed, 01 Aug 2001 19:35:15 -0400
Neil Padgett <npadgett@redhat.com>
Re: Patch for Improved Syntax Error Reporting
Neil Padgett <npadgett@redhat.com> writes:
> This is exactly what I want. If you don't have a new client, it looks
> like a message with some funk on the end. If you have a new, friendly
> client, it will strip out the field/value list at the end. Exactly the
> same as the multi-line list, really. And the translation complaint is
> equally applicable to either format.

Agreed --- as long as the *only* thing you want to add is a syntax error
location, that way would be better.  But it doesn't scale...

>> --- distinguishing the actual error message from tips/hints about what
>> to do about it.  There are a fair number of these already, and right
>> now there's just a very weak formatting convention that hints
>> appear on a separate line.

> I didn't know that such a convention exists already -- how would these
> hints look under your proposed new format?

Well, it's a pretty weak convention, but here are a couple of examples
of what I'm talking about:

    elog(ERROR, "_bt_getstackbuf: my bits moved right off the end of the world!"
                 "\n\tRecreate index %s.", RelationGetRelationName(rel));

    elog(ERROR, "Left hand side of operator '%s' has an unknown type"
         "\n\tProbably a bad attribute name", op);

    elog(ERROR, "Unable to identify a %s operator '%s' for type '%s'"
         "\n\tYou may need to add parentheses or an explicit cast",
         (is_left_op ? "left" : "right"),
         op, typeidTypeName(arg));

In all these cases, I'd call the added-on lines hints --- they're not
part of the basic error message, and the hint may not be applicable
to your particular situation.  Without wanting to start an argument
as to the validity of these particular hints, I do think that it'd
be a good idea to distinguish them from the primary error message.
In the first example, where I'd like to see us end up is something
like:

ERROR: Internal error, please report to pgsql-bugs
DETAIL: my bits moved right off the end of the world!
HINT: Recreate index foo
CODELOCATION: _bt_getstackbuf: src/backend/access/nbtree/nbtinsert.c, line 551

I'm not wedded to these particular keywords, but hopefully this will
serve as an illustration that we're cramming a lot of stuff into an
error message already.  Breaking it out into fields could render it
more intelligible, not less so --- and with an updated client, a user
could choose not to look at the info he doesn't want.  Right now he
has no real prospect of suppressing unwanted info.  An example is the
source routine name that we cram into many messages, as a poor man's
substitute for accurate error location info.  That's pretty much useless
to non-hackers, and ought to be moved out to a secondary field.

> Why aren't we using numerics to do this?

Why, thanks for reminding me.  Adding a standardized error code (not
message) that client programs could interpret is another thing that
is on the TODO list.  Seems like another application for a separable
field of an error report.  I think we should keep such codes separate
from the (localizable) message text, however.  Peter E. made some cogent
arguments that trying to drive localization off error numbers would be
a losing proposition, as opposed to using gettext().

> Would the elog call be changed to support passing in a list of
> arguments?

That hadn't really been decided, but clearly some change of the elog
API will be needed.  I think there is more about this in the archives
than you will find in TODO.detail/elog.

> We should probably introduce
> a new call, say, eelog (for enhanced error log) that takes such a list,
> and then we could define elog as a macro which calls eelog with suitable
> defaults for use with "legacy" messages. Then, we wouldn't need to go
> after every error message right away.

Yeah, the $64 question is how to avoid needing a "big bang" changeover
of all the elog calls.  Even if we wanted to try that, it'd be a
continuing headache for user-added datatypes and such.  I'd like to be
able to leave the existing elog() API in place for a few releases, if
possible.

> The question this brings up is whether a logging change can / should be
> tackled in this release. Specifically, with the current state of
> internationalization work, is it best to do it now, or later?

I'm still pointing towards 7.2 beta near the end of the month, which
would be a mighty tight schedule for anything ambitious in elog rework.
On the other hand, there's no harm in working out a design now with
the intention of starting to implement it in the 7.3 cycle.

			regards, tom lane

Wed, 01 Aug 2001 20:38:49 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: Patch for Improved Syntax Error Reporting 
> But how do they display error messages now?  Can't they just continue
> doing that with this new code?  Do we want to make them code their own
> error handling, and for what little benefit?  Let them figure out how to
> display the error in fixed-width font and be done with it.  I am sure
> they have bigger things to do than colorize error locations.

My 2c:

Why not do tom's suggestion for the POSITION: n thing, and modify psql to
strip out that header, and output the relevant part of the sql with a caret
highlighting the error position.

This will make it so that writers of the guis and format errors how they
like, and users of the most popular text interface (psql) get human-readable
results...

ie. best of both worlds...

Chris


Thu, 2 Aug 2001 10:27:22 +0800
"Christopher Kings-Lynne" <chriskl@familyhealth.com.au>
RE: Patch for Improved Syntax Error Reporting
> > But how do they display error messages now?  Can't they just continue
> > doing that with this new code?  Do we want to make them code their own
> > error handling, and for what little benefit?  Let them figure out how to
> > display the error in fixed-width font and be done with it.  I am sure
> > they have bigger things to do than colorize error locations.
> 
> My 2c:
> 
> Why not do tom's suggestion for the POSITION: n thing, and modify psql to
> strip out that header, and output the relevant part of the sql with a caret
> highlighting the error position.
> 
> This will make it so that writers of the guis and format errors how they
> like, and users of the most popular text interface (psql) get human-readable
> results...
> 
> ie. best of both worlds...

OK, I withdraw my objection.

Also, I like the idea of adding Hints and Function/line numbers to the
output too.  The offset of the error would work into that system.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Wed, 1 Aug 2001 22:39:49 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Patch for Improved Syntax Error Reporting
> > My 2c:
> > 
> > Why not do tom's suggestion for the POSITION: n thing, and modify psql to
> > strip out that header, and output the relevant part of the sql with a caret
> > highlighting the error position.
> > 
> > This will make it so that writers of the guis and format errors how they
> > like, and users of the most popular text interface (psql) get human-readable
> > results...
> > 
> > ie. best of both worlds...
> 
> OK, I withdraw my objection.
> 
> Also, I like the idea of adding Hints and Function/line numbers to the
> output too.  The offset of the error would work into that system.

I guess the thing that bothered me is that 90% of our interfaces are
just going to throw the carret under the error line and this patch
requires us to modify all the client interfaces to do that, just to
allow 10% to customize their display.

Now, I know we are going to allow elog() to generate filename, line
number, and function name as optional output information.  We could have
a SET paramter like:

	SET SYSOUTPUT TO "message, function, offset"

and this displays:

	ERROR: lkjasdf
	FUNCTION: lkjasdf
	OFFSET: 2343

and we could have an option for HIGHLIGHT:

	HIGHLIGHT: FROM tab1, tab2
	HIGHLIGHT:      ^^^^

We could control this via GUC or via the client startup code, and
clients could grab whatever they want to know about an error.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

Thu, 2 Aug 2001 12:29:34 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Patch for Improved Syntax Error Reporting
Bruce Momjian wrote:
> 
> > > My 2c:
> > >
> > > Why not do tom's suggestion for the POSITION: n thing, and modify psql to
> > > strip out that header, and output the relevant part of the sql with a caret
> > > highlighting the error position.
> > >
> > > This will make it so that writers of the guis and format errors how they
> > > like, and users of the most popular text interface (psql) get human-readable
> > > results...
> > >
> > > ie. best of both worlds...
> >
> > OK, I withdraw my objection.
> >
> > Also, I like the idea of adding Hints and Function/line numbers to the
> > output too.  The offset of the error would work into that system.
> 
> I guess the thing that bothered me is that 90% of our interfaces are
> just going to throw the carret under the error line and this patch
> requires us to modify all the client interfaces to do that, just to
> allow 10% to customize their display.
> 
> Now, I know we are going to allow elog() to generate filename, line
> number, and function name as optional output information.  We could have
> a SET paramter like:
> 
>         SET SYSOUTPUT TO "message, function, offset"
> 
> and this displays:
> 
>         ERROR: lkjasdf
>         FUNCTION: lkjasdf
>         OFFSET: 2343
> 
> and we could have an option for HIGHLIGHT:
> 
>         HIGHLIGHT: FROM tab1, tab2
>         HIGHLIGHT:      ^^^^
> 
> We could control this via GUC or via the client startup code, and
> clients could grab whatever they want to know about an error.

I think it seems that we all have a general idea of where we want to go
with this. How about the following as a plan to get this ready for 7.2:

1. Leave elog() alone.
2. For syntax error reporting, and syntax error reporting alone, output
the error message in the new, multi-line format from the backend.
3. Add functionality to psql for parsing the multi-line format error
messages. (Probably this will form a reusable function library that
other utilities can use.)
4. Modify psql to use this new functionality, but only for processing
parse errors -- all other messages will be handled as is.

Thoughts?

Neil

-- 
Neil Padgett
Red Hat Canada Ltd.                       E-Mail:  npadgett@redhat.com
2323 Yonge Street, Suite #300, 
Toronto, ON  M4P 2C9

Thu, 02 Aug 2001 13:07:10 -0400
Neil Padgett <npadgett@redhat.com>
Re: Patch for Improved Syntax Error Reporting
Neil Padgett <npadgett@redhat.com> writes:
> I think it seems that we all have a general idea of where we want to go
> with this. How about the following as a plan to get this ready for 7.2:

> 1. Leave elog() alone.
> 2. For syntax error reporting, and syntax error reporting alone, output
> the error message in the new, multi-line format from the backend.
> 3. Add functionality to psql for parsing the multi-line format error
> messages. (Probably this will form a reusable function library that
> other utilities can use.)
> 4. Modify psql to use this new functionality, but only for processing
> parse errors -- all other messages will be handled as is.

That seems like a good plan --- forward progress, and doable within the
7.2 time frame.

I think the thing we need to nail down next is the changes in the wire
protocol --- specifically, how the "multi line format" of error messages
will be defined.  We don't necessarily need to define all the field
keywords yet, but we do need to have a clear idea of the format rules
and the parsing algorithm that clients will use.  This might be trickier
than it seems at first glance, because we need both backwards and
forwards compatibility if we are to avoid a protocol version bump: not
only must old clients accept the new syntax (which is a no-op), but
new clients should behave reasonably well when fed messages from an old
backend (which might not adhere perfectly to the new syntax definition).

I'd suggest drawing up a straw-man definition and posting it on
pghackers and/or pginterfaces for comment.

Another thing to think about (orthogonally to the wire protocol) is
where on the client side to do the parsing.  IMHO it'd be a good idea to
put as much of it as we can into libpq, where it'll be available
automatically to non-psql applications.  Again, though, compatibility
is an issue.

			regards, tom lane

Thu, 02 Aug 2001 16:28:03 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Re: Patch for Improved Syntax Error Reporting 
> That seems like a good plan --- forward progress, and doable within the
> 7.2 time frame.

Just a quick question - when does stuff need to be in for 7.2?  I've been
sitting on this ADD UNIQUE patch for a while.  There's just a few little
things in its behaviour that need to be changed.  Like, letting ppl add
unique(a,b) and unique (b,a) plus warn if there's an existing non-unique
index...

I'm just finding it really hard to find time to fiddle with it - how long do
I have before 7.2alpha?

Chris


Fri, 3 Aug 2001 09:30:57 +0800
"Christopher Kings-Lynne" <chriskl@familyhealth.com.au>
RE: Patch for Improved Syntax Error Reporting 
"Christopher Kings-Lynne" <chriskl@familyhealth.com.au> writes:
> Just a quick question - when does stuff need to be in for 7.2?

There's not an agreed schedule yet.  Personally I'd like to see us
release a beta before I go off to LinuxWorld (8/28) ... it'd be nice
to be able to say "7.2 is in beta" at the show.  But that's just my
two cents.  There's been no core discussion yet beyond agreeing a
couple months ago that "end of the summer feels about right".

But anyway, if that seems like a reasonable goal then it'd be nice
to have all new-feature patches in by mid-month or so, so that we
could buckle down to alpha-testing and bug fixes.  How's that fit
with your schedule?

			regards, tom lane

Thu, 02 Aug 2001 22:55:50 -0400
Tom Lane <tgl@sss.pgh.pa.us>
Schedule (was Re: [PATCHES] Patch for Improved Syntax Error
 Reporting)
Neil Padgett writes:

> 1. Leave elog() alone.
> 2. For syntax error reporting, and syntax error reporting alone, output
> the error message in the new, multi-line format from the backend.
> 3. Add functionality to psql for parsing the multi-line format error
> messages. (Probably this will form a reusable function library that
> other utilities can use.)
> 4. Modify psql to use this new functionality, but only for processing
> parse errors -- all other messages will be handled as is.

We've had a discussion a month or two ago about rearranging error and
notice packets into key/value pairs, which would contain error codes,
command string positions, and what not.  I opined that this would require
a wire protocol change.  I do not like the alternative suggestion of
separating these pairs by newlines or some such.  That puts a rather
peculiar (and possibly not automatically enforcable) restriction on the
allowable contents of the message texts.  Note that message texts can
contain parse or plan trees, which can contain all kinds of funny line
noise.  A protocol change isn't the end of the world, so please consider
it.

Btw., there's something in the SQL standard about all of this.  I can tell
you more once I'm done reading back emails.

-- 
Peter Eisentraut   peter_e@gmx.net   http://funkturm.homeip.net/~peter


Sun, 5 Aug 2001 22:37:18 +0200 (CEST)
Peter Eisentraut <peter_e@gmx.net>
Re: Patch for Improved Syntax Error Reporting