database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-07 00:36:50 +03:00
Code Activity

Rethink the order of expression preprocessing: eval_const_expressions

Browse Source 
really ought to run before canonicalize_qual, because it can now produce
forms that canonicalize_qual knows how to improve (eg, NOT clauses).
Also, because eval_const_expressions already knows about flattening
nested ANDs and ORs into N-argument form, the initial flatten_andors
pass in canonicalize_qual is now completely redundant and can be
removed.  This doesn't save a whole lot of code, but the time and
palloc traffic eliminated is a useful gain on large expression trees.
This commit is contained in:
Tom Lane
2005-03-28 00:58:26 +00:00
parent bf3dbb5881
commit 5db2e83852
7 changed files with 61 additions and 140 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
src/backend/optimizer/plan/planner.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.180 2005/03/17 23:44:26 neilc Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.181 2005/03/28 00:58:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -422,13 +422,17 @@ preprocess_expression(Query *parse, Node *expr, int kind)
expr = flatten_join_alias_vars(parse, expr);
/*
* If it's a qual or havingQual, canonicalize it. It seems most
* useful to do this before applying eval_const_expressions, since the
* latter can optimize flattened AND/ORs better than unflattened ones.
* Simplify constant expressions.
*
* Note: all processing of a qual expression after this point must be
* careful to maintain AND/OR flatness --- that is, do not generate a
* tree with AND directly under AND, nor OR directly under OR.
* Note: this also flattens nested AND and OR expressions into N-argument
* form. All processing of a qual expression after this point must be
* careful to maintain AND/OR flatness --- that is, do not generate a tree
* with AND directly under AND, nor OR directly under OR.
*/
expr = eval_const_expressions(expr);
/*
* If it's a qual or havingQual, canonicalize it.
*/
if (kind == EXPRKIND_QUAL)
{
@ -440,11 +444,6 @@ preprocess_expression(Query *parse, Node *expr, int kind)
#endif
}
/*
* Simplify constant expressions.
*/
expr = eval_const_expressions(expr);
/* Expand SubLinks to SubPlans */
if (parse->hasSubLinks)
expr = SS_process_sublinks(expr, (kind == EXPRKIND_QUAL));