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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2010-11-12 15:14:51 -0500 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2010-11-12 15:18:54 -0500 |
| commit | c26bc6919efedd0d1e8d9550a05c111dac0830fe (patch) | |
| tree | 40068cc4be067ddca8339509ed8878d159860c6e /src | |
| parent | 3ef6ea3dcefebb515207d1009d81ce1d80cb1b29 (diff) | |
| download | postgresql-c26bc6919efedd0d1e8d9550a05c111dac0830fe.tar.gz postgresql-c26bc6919efedd0d1e8d9550a05c111dac0830fe.zip | |
Fix old oversight in const-simplification of COALESCE() expressions.
Once we have found a non-null constant argument, there is no need to
examine additional arguments of the COALESCE. The previous coding got it
right only if the constant was in the first argument position; otherwise
it tried to simplify following arguments too, leading to unexpected
behavior like this:
regression=# select coalesce(f1, 42, 1/0) from int4_tbl;
ERROR: division by zero
It's a minor corner case, but a bug is a bug, so back-patch all the way.
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/util/clauses.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index 1a06839e734..3268ec89799 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -2022,7 +2022,9 @@ eval_const_expressions_mutator(Node *node, /* * We can remove null constants from the list. For a non-null * constant, if it has not been preceded by any other - * non-null-constant expressions then that is the result. + * non-null-constant expressions then it is the result. Otherwise, + * it's the next argument, but we can drop following arguments + * since they will never be reached. */ if (IsA(e, Const)) { @@ -2030,6 +2032,8 @@ eval_const_expressions_mutator(Node *node, continue; /* drop null constant */ if (newargs == NIL) return e; /* first expr */ + newargs = lappend(newargs, e); + break; } newargs = lappend(newargs, e); } |