From 3e2e0d5ad7fcb89d18a71cbfc885ef184e1b6f2e Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Fri, 22 Dec 2023 21:44:55 +0100 Subject: [PATCH] Set all variable-length fields of pg_attribute to null on column drop When a column is dropped, the fields attacl, attoptions, and attfdwoptions were kept unchanged. This is probably harmless, but it seems wasteful, and leaves potentially dangling data lying around (for example, attacl could contain references to users that are later also dropped). Change this to set those fields to null when a column is marked as dropped. Reviewed-by: Alvaro Herrera Discussion: https://www.postgresql.org/message-id/flat/249d819d-1763-4580-8110-0bf91a0f08b7@eisentraut.org --- src/backend/catalog/heap.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c index 7224d966950..b93894889d6 100644 --- a/src/backend/catalog/heap.c +++ b/src/backend/catalog/heap.c @@ -1647,6 +1647,9 @@ RemoveAttributeById(Oid relid, AttrNumber attnum) HeapTuple tuple; Form_pg_attribute attStruct; char newattname[NAMEDATALEN]; + Datum valuesAtt[Natts_pg_attribute] = {0}; + bool nullsAtt[Natts_pg_attribute] = {0}; + bool replacesAtt[Natts_pg_attribute] = {0}; /* * Grab an exclusive lock on the target table, which we will NOT release @@ -1695,24 +1698,24 @@ RemoveAttributeById(Oid relid, AttrNumber attnum) "........pg.dropped.%d........", attnum); namestrcpy(&(attStruct->attname), newattname); - /* clear the missing value if any */ - if (attStruct->atthasmissing) - { - Datum valuesAtt[Natts_pg_attribute] = {0}; - bool nullsAtt[Natts_pg_attribute] = {0}; - bool replacesAtt[Natts_pg_attribute] = {0}; + /* Clear the missing value */ + attStruct->atthasmissing = false; + nullsAtt[Anum_pg_attribute_attmissingval - 1] = true; + replacesAtt[Anum_pg_attribute_attmissingval - 1] = true; - /* update the tuple - set atthasmissing and attmissingval */ - valuesAtt[Anum_pg_attribute_atthasmissing - 1] = - BoolGetDatum(false); - replacesAtt[Anum_pg_attribute_atthasmissing - 1] = true; - valuesAtt[Anum_pg_attribute_attmissingval - 1] = (Datum) 0; - nullsAtt[Anum_pg_attribute_attmissingval - 1] = true; - replacesAtt[Anum_pg_attribute_attmissingval - 1] = true; + /* + * Clear the other variable-length fields. This saves some space in + * pg_attribute and removes no longer useful information. + */ + nullsAtt[Anum_pg_attribute_attacl - 1] = true; + replacesAtt[Anum_pg_attribute_attacl - 1] = true; + nullsAtt[Anum_pg_attribute_attoptions - 1] = true; + replacesAtt[Anum_pg_attribute_attoptions - 1] = true; + nullsAtt[Anum_pg_attribute_attfdwoptions - 1] = true; + replacesAtt[Anum_pg_attribute_attfdwoptions - 1] = true; - tuple = heap_modify_tuple(tuple, RelationGetDescr(attr_rel), - valuesAtt, nullsAtt, replacesAtt); - } + tuple = heap_modify_tuple(tuple, RelationGetDescr(attr_rel), + valuesAtt, nullsAtt, replacesAtt); CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);