diff options
Diffstat (limited to 'src/backend/optimizer/prep/prepjointree.c')
| -rw-r--r-- | src/backend/optimizer/prep/prepjointree.c | 24 |
1 files changed, 15 insertions, 9 deletions
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c index 90485171d97..033aaba494e 100644 --- a/src/backend/optimizer/prep/prepjointree.c +++ b/src/backend/optimizer/prep/prepjointree.c @@ -16,7 +16,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.15 2004/01/10 00:30:21 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepjointree.c,v 1.16 2004/01/10 18:13:53 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -439,11 +439,13 @@ is_simple_subquery(Query *subquery) /* * has_nullable_targetlist * Check a subquery in the range table to see if all the non-junk - * targetlist items are simple variables (and, hence, will correctly - * go to NULL when examined above the point of an outer join). + * targetlist items are simple variables or strict functions of simple + * variables (and, hence, will correctly go to NULL when examined above + * the point of an outer join). * - * A possible future extension is to accept strict functions of simple - * variables, eg, "x + 1". + * NOTE: it would be correct (and useful) to ignore output columns that aren't + * actually referenced by the enclosing query ... but we do not have that + * information available at this point. */ static bool has_nullable_targetlist(Query *subquery) @@ -458,11 +460,15 @@ has_nullable_targetlist(Query *subquery) if (tle->resdom->resjunk) continue; - /* Okay if tlist item is a simple Var */ - if (tle->expr && IsA(tle->expr, Var)) - continue; + /* Must contain a Var of current level */ + if (!contain_vars_of_level((Node *) tle->expr, 0)) + return false; - return false; + /* Must not contain any non-strict constructs */ + if (contain_nonstrict_functions((Node *) tle->expr)) + return false; + + /* This one's OK, keep scanning */ } return true; } |