postgres.git / summary / log / commit / refs

commit    570e2fcc041a55ba8991a640cc3f3f0e122feac3
Author:   Robert Haas <rhaas@postgresql.org>
Date:     Tue Mar 24 10:11:15 2026 +0000

    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
    Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
    Discussion: http://postgr.es/m/CA+TgmoacixUZVvi00hOjk_d9B4iYKswWP1gNqQ8Vfray-AcOCA@mail.gmail.com


 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 ?


[parent: d2a1aa77c255]