postgres.git / summary / log / commit / refs

commit    ae89129aa3555c263b8c3ccc4c0f1ef7e46201aa
Author:   David Rowley <drowley@postgresql.org>
Date:     Mon Aug 07 10:14:54 2023 +0000
First released in: 17.0, 14.9, 15.4, 16.0

    Don't Memoize lateral joins with volatile join conditions
    
    The use of Memoize was already disabled in normal joins when the join
    conditions had volatile functions per the code in
    match_opclause_to_indexcol().  Ordinarily, the parameterization for the
    inner side of a nested loop will be an Index Scan or at least eventually
    lead to an index scan (perhaps nested several joins deep). However, for
    lateral joins, that's not the case and seq scans can be parameterized
    too, so we can't rely on match_opclause_to_indexcol().
    
    Here we explicitly check the parameterization for volatile functions and
    don't consider the generation of a Memoize path when such functions
    are present.
    
    Author: Richard Guo
    Discussion: https://postgr.es/m/CAMbWs49nHFnHbpepLsv_yF3qkpCS4BdB-v8HoJVv8_=Oat0u_w@mail.gmail.com
    Backpatch-through: 14, where Memoize was introduced


 src/backend/optimizer/path/joinpath.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 4b58936fa4c..03b31859847 100644
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -667,6 +667,23 @@ get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
 			return NULL;
 	}
 
+	/*
+	 * Also check the parameterized path restrictinfos for volatile functions.
+	 * Indexed functions must be immutable so shouldn't have any volatile
+	 * functions, however, with a lateral join the inner scan may not be an
+	 * index scan.
+	 */
+	if (inner_path->param_info != NULL)
+	{
+		foreach(lc, inner_path->param_info->ppi_clauses)
+		{
+			RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
+
+			if (contain_volatile_functions((Node *) rinfo))
+				return NULL;
+		}
+	}
+
 	/* Check if we have hash ops for each parameter to the path */
 	if (paraminfo_get_equal_hashops(root,
 									inner_path->param_info,


[parent: 67a007dc0cdb]