Hi everyone,
In the `clause_selectivity_ext()` function, there’s a comment regarding
a NULL clause check that asks, "can this still happen?". I decided to
investigate whether this scenario is still valid.
Here’s what I found after reviewing the relevant cases:
- approx_tuple_count(): The function iterates over a loop of other clauses.
- get_foreign_key_join_selectivity(): The function is invoked within an
`if (clause)` condition.
- consider_new_or_clause(): The clause is generated by
`make_restrictinfo()`, which never returns NULL.
- clauselist_selectivity_ext(): This function either checks
`list_length(clauses) == 1` before being called, or it is called within
a loop of clauses.
In other cases, the function is called recursively from
`clause_selectivity_ext()`.
If you are aware of any situations where a NULL clause could be passed
or if I’ve missed anything, please let me know. I’m also open to any
other suggestions.
--
Regards,
Ilia Evdokimov,
Tantor Labs LCC.
From fab0575ef1350cb700b6fc079230397ecb5ca19d Mon Sep 17 00:00:00 2001
From: Ilia Evdokimov <ilya.evdoki...@tantorlabs.ru>
Date: Mon, 19 Aug 2024 12:08:53 +0300
Subject: [PATCH] Remove redundant NULL check for clause during selectivity
calculation
The function clause_selectivity_ext() takes a Node *clause parameter,
which is either iterated over in a loop with other clauses or passed
as a RestrictInfo from other functions.
Since these functions guarantee that clause cannot be NULL,
the NULL check is unnecessary and has been removed.
---
src/backend/optimizer/path/clausesel.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
index 0ab021c1e8..5992f96ed2 100644
--- a/src/backend/optimizer/path/clausesel.c
+++ b/src/backend/optimizer/path/clausesel.c
@@ -692,9 +692,6 @@ clause_selectivity_ext(PlannerInfo *root,
RestrictInfo *rinfo = NULL;
bool cacheable = false;
- if (clause == NULL) /* can this still happen? */
- return s1;
-
if (IsA(clause, RestrictInfo))
{
rinfo = (RestrictInfo *) clause;
--
2.34.1
