title: Pandas column indexing for searching?
body: <p>In relational database, we can create index on columns to speed up querying and joining on those columns. I want to do them same thing on pandas dataframe. The row index seems not what relational database offers.</p>
  
  <p>The question is: Are columns in pandas indexed for searching by default? </p>
  
  <p>If not, is it possible to index columns manually and how to do it?</p>
  
  <p>Edit: I have read pandas docs and searched everywhere, but no one mentions indexing and searching/merging performance on pandas. Seem no one care about this issue, although it is critical in relational database. Can any one make a statement about indexing and performance on pandas?</p>
  
  <p>Thanks.</p>