/// Create a new instance of Join
///
/// `left` and `right` are the left and right parents respectively. `on` is a tuple specifying
/// the join columns: (left_parent_column, right_parent_column) and `emit` dictates for each
/// output colunm, which source and column should be used (true means left parent, and false
/// means right parent).
Create a new instance of Join
`left` and `right` are the left and right parents respectively. `on` is a tuple specifying
the join columns: (left_parent_column, right_parent_column) and `emit` dictates for each
output colunm, which source and column should be used (true means left parent, and false
means right parent).
Create a new instance of Join ` left ` and ` right ` are the left and right parents respectively . ` on ` is a tuple specifying the join columns : ( left_parent_column right_parent_column ) and ` emit ` dictates for each output colunm which source and column should be used ( true means left parent and false means right parent ) .
pub fn new(left: NodeIndex, right: NodeIndex, kind: JoinType, emit: Vec<JoinSource>) -> Self {
        let mut join_columns = Vec::new();
        let emit: Vec<_> = emit
            .into_iter()
            .map(|join_source| match join_source {
                JoinSource::L(c) => (true, c),
                JoinSource::R(c) => (false, c),
                JoinSource::B(lc, rc) => {
                    join_columns.push((lc, rc));
                    (true, lc)
                }
            })
            .collect();
        assert_eq!(join_columns.len(), 1, "only supports single column joins");
        let on = *join_columns.iter().next().unwrap();
        let (in_place_left_emit, in_place_right_emit) = {
            let compute_in_place_emit = |left| {
                let num_columns = emit
                    .iter()
                    .filter(|&&(from_left, _)| from_left == left)
                    .map(|&(_, c)| c + 1)
                    .max()
                    .unwrap_or(0);
                // Tracks how columns have moved. At any point during the iteration, column i in
                // the original row will be located at position remap[i].
                let mut remap: Vec<_> = (0..num_columns).collect();
                emit.iter()
                    .enumerate()
                    .map(|(i, &(from_left, c))| {
                        if from_left == left {
                            let remapped = remap[c];
                            let other = remap.iter().position(|&c| c == i);
                            // Columns can't appear multiple times in join output!
                            assert!((remapped >= i) || (emit[remapped].0 != left));
                            remap[c] = i;
                            if let Some(other) = other {
                                remap[other] = remapped;
                            }
                            (from_left, remapped)
                        } else {
                            (from_left, c)
                        }
                    })
                    .collect::<Vec<_>>()
            };
            (compute_in_place_emit(true), compute_in_place_emit(false))
        };
        Self {
            left: left.into(),
            right: right.into(),
            on,
            emit,
            in_place_left_emit,
            in_place_right_emit,
            kind,
        }
    }
pub fn new ( left : NodeIndex , right : NodeIndex , kind : JoinType , emit : Vec < JoinSource > ) -> Self { let mut join_columns = Vec :: new ( ) ; let emit : Vec < _ > = emit . into_iter ( ) . map ( | join_source | match join_source { JoinSource :: L ( c ) => ( true , c ) , JoinSource :: R ( c ) => ( false , c ) , JoinSource :: B ( lc , rc ) => { join_columns . push ( ( lc , rc ) ) ; ( true , lc ) } } ) . collect ( ) ; assert_eq ! ( join_columns len ( ) 1 " " ) ; let on = * join_columns . iter ( ) . next ( ) . unwrap ( ) ; let ( in_place_left_emit , in_place_right_emit ) = { let compute_in_place_emit = | left | { let num_columns = emit . iter ( ) . filter ( | & & ( from_left , _ ) | from_left == left ) . map ( | & ( _ , c ) | c + 1 ) . max ( ) . unwrap_or ( 0 ) ; // Tracks how columns have moved. At any point during the iteration, column i in // the original row will be located at position remap[i]. let mut remap : Vec < _ > = ( 0 .. num_columns ) . collect ( ) ; emit . iter ( ) . enumerate ( ) . map ( | ( i , & ( from_left , c ) ) | { if from_left == left { let remapped = remap [ c ] ; let other = remap . iter ( ) . position ( | & c | c == i ) ; // Columns can't appear multiple times in join output! assert ! ( ( remapped i ) ( emit [ remapped ] 0 left ) ) ; remap [ c ] = i ; if let Some ( other ) = other { remap [ other ] = remapped ; } ( from_left , remapped ) } else { ( from_left , c ) } } ) . collect :: < Vec < _ > > ( ) } ; ( compute_in_place_emit ( true ) , compute_in_place_emit ( false ) ) } ; Self { left : left . into ( ) , right : right . into ( ) , on , emit , in_place_left_emit , in_place_right_emit , kind , } }
Create a new instance of Join
`left` and `right` are the left and right parents respectively.
Create a new instance of Join ` left ` and ` right ` are the left and right parents respectively .
left
NodeIndex
right
NodeIndex
kind
JoinType
emit
Vec<JoinSource>