diff options
Diffstat (limited to 'src/backend/optimizer/util/clauses.c')
| -rw-r--r-- | src/backend/optimizer/util/clauses.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index cf585cccbc8..15418d4e957 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.189 2005/03/27 19:18:02 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.190 2005/03/28 00:58:24 tgl Exp $ * * HISTORY * AUTHOR DATE MAJOR EVENT @@ -1190,6 +1190,9 @@ rowtype_field_matches(Oid rowtypeid, int fieldnum, * * We assume that the tree has already been type-checked and contains * only operators and functions that are reasonable to try to execute. + * + * NOTE: the planner assumes that this will always flatten nested AND and + * OR clauses into N-argument form. See comments in prepqual.c. *-------------------- */ Node * @@ -1871,7 +1874,7 @@ eval_const_expressions_mutator(Node *node, * is TRUE and at least one is NULL. * * This is split out as a subroutine so that we can recurse to fold sub-ORs - * into the upper OR clause, thereby preserving AND/OR flatness. + * into the upper OR clause, thereby ensuring that nested ORs are flattened. * * The output arguments *haveNull and *forceTrue must be initialized FALSE * by the caller. They will be set TRUE if a null constant or true constant, @@ -1931,7 +1934,7 @@ simplify_or_arguments(List *args, bool *haveNull, bool *forceTrue) * is FALSE and at least one is NULL. * * This is split out as a subroutine so that we can recurse to fold sub-ANDs - * into the upper AND clause, thereby preserving AND/OR flatness. + * into the upper AND clause, thereby ensuring that nested ANDs are flattened. * * The output arguments *haveNull and *forceFalse must be initialized FALSE * by the caller. They will be set TRUE if a null constant or false constant, |