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commit    e3a27fd06d06726546bccf22ac986c67f0e84dd5
Author:   Michael Paquier <michael@paquier.xyz>
Date:     Mon Dec 30 04:33:59 2024 +0000
First released in: 18.0, 15.11, 16.7, 17.3

    Fix memory leak in pgoutput with relation attribute map
    
    pgoutput caches the attribute map of a relation, that is free()'d only
    when validating a RelationSyncEntry.  However, this code path is not
    taken when calling any of the SQL functions able to do some logical
    decoding, like pg_logical_slot_{get,peek}_changes(), leaking some memory
    into CacheMemoryContext on repeated calls.
    
    To address this, a relation's attribute map is allocated in
    PGOutputData's cachectx, free()'d at the end of the execution of these
    SQL functions when logical decoding ends.  This is available down to 15.
    v13 and v14 have a similar leak, which will be dealt with later.
    
    Reported-by: Masahiko Sawada
    Author: Vignesh C
    Reviewed-by: Hou Zhijie
    Discussion: https://postgr.es/m/CAD21AoDkAhQVSukOfH3_reuF-j4EU0-HxMqU3dU+bSTxsqT14Q@mail.gmail.com
    Discussion: https://postgr.es/m/CALDaNm1hewNAsZ_e6FF52a=9drmkRJxtEPrzCB6-9mkJyeBBqA@mail.gmail.com
    Backpatch-through: 15


 src/backend/replication/pgoutput/pgoutput.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index c9ae239aa4e..32b74bb4752 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -1179,8 +1179,8 @@ init_tuple_slot(PGOutputData *data, Relation relation,
 		TupleDesc	indesc = RelationGetDescr(relation);
 		TupleDesc	outdesc = RelationGetDescr(ancestor);
 
-		/* Map must live as long as the session does. */
-		oldctx = MemoryContextSwitchTo(CacheMemoryContext);
+		/* Map must live as long as the logical decoding context. */
+		oldctx = MemoryContextSwitchTo(data->cachectx);
 
 		entry->attrmap = build_attrmap_by_name_if_req(indesc, outdesc, false);
 


[parent: 359f31c638eb]