From 36829f53acbbadb0e24254952a6d6ec036f41639 Mon Sep 17 00:00:00 2001 From: Robert Haas Date: Fri, 20 Mar 2026 11:09:44 -0400 Subject: [PATCH v1 1/3] Prevent spurious "indexes on virtual generated columns are not supported". Both of the checks in DefineIndex() that can produce this error message have a guard against negative attribute numbers, but lack a guard to ensure that attno is non-zero. As a result, we can index off the beginning of the TupleDesc and read a garbage byte for attgenerated. If that byte happens to be 'v', we'll incorrectly produce the error mentioned above. The first call site is easy to hit: any attempt to create an expression index does so. The second one is not currently hit in the regression tests, but can be hit by something like CREATE INDEX ON some_table ((some_function(some_table))). Found by study of a test_plan_advice failure on buildfarm member skink, though this issue has nothing to do with test_plan_advice and seems to have only been revealed by happenstance. Backpatch-through: 18 --- src/backend/commands/indexcmds.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c index b89c6855364..dd593ccbc1c 100644 --- a/src/backend/commands/indexcmds.c +++ b/src/backend/commands/indexcmds.c @@ -1123,7 +1123,8 @@ DefineIndex(ParseState *pstate, errmsg("index creation on system columns is not supported"))); - if (TupleDescAttr(RelationGetDescr(rel), attno - 1)->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL) + if (attno > 0 && + TupleDescAttr(RelationGetDescr(rel), attno - 1)->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL) ereport(ERROR, errcode(ERRCODE_FEATURE_NOT_SUPPORTED), stmt->primary ? @@ -1164,7 +1165,8 @@ DefineIndex(ParseState *pstate, { AttrNumber attno = j + FirstLowInvalidHeapAttributeNumber; - if (TupleDescAttr(RelationGetDescr(rel), attno - 1)->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL) + if (attno > 0 && + TupleDescAttr(RelationGetDescr(rel), attno - 1)->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), stmt->isconstraint ? -- 2.51.0