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Replace BackendIds with 0-based ProcNumbers

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Now that BackendId was just another index into the proc array, it was
redundant with the 0-based proc numbers used in other places. Replace
all usage of backend IDs with proc numbers.

The only place where the term "backend id" remains is in a few pgstat
functions that expose backend IDs at the SQL level. Those IDs are now
in fact 0-based ProcNumbers too, but the documentation still calls
them "backend ids". That term still seems appropriate to describe what
the numbers are, so I let it be.

One user-visible effect is that pg_temp_0 is now a valid temp schema
name, for backend with ProcNumber 0.

Reviewed-by: Andres Freund
Discussion: https://www.postgresql.org/message-id/8171f1aa-496f-46a6-afc3-c46fe7a9b407@iki.fi
This commit is contained in:
Heikki Linnakangas
2024-03-03 19:38:22 +02:00
parent ab355e3a88
commit 024c521117
71 changed files with 571 additions and 579 deletions
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4
src/backend/utils/cache/inval.c vendored
View File

@@ -1453,8 +1453,8 @@ CacheInvalidateRelcacheByRelid(Oid relid)
* replaying WAL as well as when creating it.
*
* Note: In order to avoid bloating SharedInvalidationMessage, we store only
* three bytes of the backend ID using what would otherwise be padding space.
* Thus, the maximum possible backend ID is 2^23-1.
* three bytes of the ProcNumber using what would otherwise be padding space.
* Thus, the maximum possible ProcNumber is 2^23-1.
*/
void
CacheInvalidateSmgr(RelFileLocatorBackend rlocator)

30
src/backend/utils/cache/relcache.c vendored
View File

@@ -1144,13 +1144,13 @@ retry:
{
case RELPERSISTENCE_UNLOGGED:
case RELPERSISTENCE_PERMANENT:
relation->rd_backend = InvalidBackendId;
relation->rd_backend = INVALID_PROC_NUMBER;
relation->rd_islocaltemp = false;
break;
case RELPERSISTENCE_TEMP:
if (isTempOrTempToastNamespace(relation->rd_rel->relnamespace))
{
relation->rd_backend = BackendIdForTempRelations();
relation->rd_backend = ProcNumberForTempRelations();
relation->rd_islocaltemp = true;
}
else
@@ -1159,18 +1159,18 @@ retry:
* If it's a temp table, but not one of ours, we have to use
* the slow, grotty method to figure out the owning backend.
*
* Note: it's possible that rd_backend gets set to MyBackendId
* here, in case we are looking at a pg_class entry left over
* from a crashed backend that coincidentally had the same
* BackendId we're using. We should *not* consider such a
* table to be "ours"; this is why we need the separate
* rd_islocaltemp flag. The pg_class entry will get flushed
* if/when we clean out the corresponding temp table namespace
* in preparation for using it.
* Note: it's possible that rd_backend gets set to
* MyProcNumber here, in case we are looking at a pg_class
* entry left over from a crashed backend that coincidentally
* had the same ProcNumber we're using. We should *not*
* consider such a table to be "ours"; this is why we need the
* separate rd_islocaltemp flag. The pg_class entry will get
* flushed if/when we clean out the corresponding temp table
* namespace in preparation for using it.
*/
relation->rd_backend =
GetTempNamespaceBackendId(relation->rd_rel->relnamespace);
Assert(relation->rd_backend != InvalidBackendId);
GetTempNamespaceProcNumber(relation->rd_rel->relnamespace);
Assert(relation->rd_backend != INVALID_PROC_NUMBER);
relation->rd_islocaltemp = false;
}
break;
@@ -1896,7 +1896,7 @@ formrdesc(const char *relationName, Oid relationReltype,
relation->rd_newRelfilelocatorSubid = InvalidSubTransactionId;
relation->rd_firstRelfilelocatorSubid = InvalidSubTransactionId;
relation->rd_droppedSubid = InvalidSubTransactionId;
relation->rd_backend = InvalidBackendId;
relation->rd_backend = INVALID_PROC_NUMBER;
relation->rd_islocaltemp = false;
/*
@@ -3611,12 +3611,12 @@ RelationBuildLocalRelation(const char *relname,
{
case RELPERSISTENCE_UNLOGGED:
case RELPERSISTENCE_PERMANENT:
rel->rd_backend = InvalidBackendId;
rel->rd_backend = INVALID_PROC_NUMBER;
rel->rd_islocaltemp = false;
break;
case RELPERSISTENCE_TEMP:
Assert(isTempOrTempToastNamespace(relnamespace));
rel->rd_backend = BackendIdForTempRelations();
rel->rd_backend = ProcNumberForTempRelations();
rel->rd_islocaltemp = true;
break;
default: