diff options
| author | Peter Eisentraut <peter@eisentraut.org> | 2024-08-08 08:27:26 +0200 |
|---|---|---|
| committer | Peter Eisentraut <peter@eisentraut.org> | 2024-09-12 10:48:39 +0200 |
| commit | 811af9786b919d7acb22ea00ecb63f47de7942cd (patch) | |
| tree | 1b075e1c0e8c49cf901a09cc02ff667dff0ef86f /src/backend/utils/cache/relfilenumbermap.c | |
| parent | 00c76cf21c42c17e60e73a87dea0d1b4e234d9da (diff) | |
Don't overwrite scan key in systable_beginscan()
When systable_beginscan() and systable_beginscan_ordered() choose an
index scan, they remap the attribute numbers in the passed-in scan
keys to the attribute numbers of the index, and then write those
remapped attribute numbers back into the scan key passed by the
caller. This second part is surprising and gratuitous. It means that
a scan key cannot safely be used more than once (but it might
sometimes work, depending on circumstances). Also, there is no value
in providing these remapped attribute numbers back to the caller,
since they can't do anything with that.
Fix that by making a copy of the scan keys passed by the caller and
make the modifications there.
Also, some code that had to work around the previous situation is
simplified.
Discussion: https://www.postgresql.org/message-id/flat/f8c739d9-f48d-4187-b214-df3391ba41ab@eisentraut.org
Diffstat (limited to 'src/backend/utils/cache/relfilenumbermap.c')
| -rw-r--r-- | src/backend/utils/cache/relfilenumbermap.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/src/backend/utils/cache/relfilenumbermap.c b/src/backend/utils/cache/relfilenumbermap.c index 9e76f745297..8dbccdb551e 100644 --- a/src/backend/utils/cache/relfilenumbermap.c +++ b/src/backend/utils/cache/relfilenumbermap.c @@ -141,7 +141,6 @@ RelidByRelfilenumber(Oid reltablespace, RelFileNumber relfilenumber) SysScanDesc scandesc; Relation relation; HeapTuple ntp; - ScanKeyData skey[2]; Oid relid; if (RelfilenumberMapHash == NULL) @@ -181,6 +180,8 @@ RelidByRelfilenumber(Oid reltablespace, RelFileNumber relfilenumber) } else { + ScanKeyData skey[2]; + /* * Not a shared table, could either be a plain relation or a * non-shared, nailed one, like e.g. pg_class. @@ -189,10 +190,8 @@ RelidByRelfilenumber(Oid reltablespace, RelFileNumber relfilenumber) /* check for plain relations by looking in pg_class */ relation = table_open(RelationRelationId, AccessShareLock); - /* copy scankey to local copy, it will be modified during the scan */ + /* copy scankey to local copy and set scan arguments */ memcpy(skey, relfilenumber_skey, sizeof(skey)); - - /* set scan arguments */ skey[0].sk_argument = ObjectIdGetDatum(reltablespace); skey[1].sk_argument = ObjectIdGetDatum(relfilenumber); |