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Combine cmin and cmax fields of HeapTupleHeaders into a single field, by

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keeping private state in each backend that has inserted and deleted the same
tuple during its current top-level transaction.  This is sufficient since
there is no need to be able to determine the cmin/cmax from any other
transaction.  This gets us back down to 23-byte headers, removing a penalty
paid in 8.0 to support subtransactions.  Patch by Heikki Linnakangas, with
minor revisions by moi, following a design hashed out awhile back on the
pghackers list.
This commit is contained in:
Tom Lane
2007-02-09 03:35:35 +00:00
parent acb3416686
commit c398300330
21 changed files with 799 additions and 127 deletions
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8
src/backend/utils/fmgr/fmgr.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.103 2007/01/05 22:19:43 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.104 2007/02/09 03:35:34 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -64,7 +64,7 @@ typedef struct
/* fn_oid is the hash key and so must be first! */
Oid fn_oid; /* OID of an external C function */
TransactionId fn_xmin; /* for checking up-to-dateness */
CommandId fn_cmin;
ItemPointerData fn_tid;
PGFunction user_fn; /* the function's address */
const Pg_finfo_record *inforec; /* address of its info record */
} CFuncHashTabEntry;
@@ -483,7 +483,7 @@ lookup_C_func(HeapTuple procedureTuple)
if (entry == NULL)
return NULL; /* no such entry */
if (entry->fn_xmin == HeapTupleHeaderGetXmin(procedureTuple->t_data) &&
entry->fn_cmin == HeapTupleHeaderGetCmin(procedureTuple->t_data))
ItemPointerEquals(&entry->fn_tid, &procedureTuple->t_self))
return entry; /* OK */
return NULL; /* entry is out of date */
}
@@ -521,7 +521,7 @@ record_C_func(HeapTuple procedureTuple,
&found);
/* OID is already filled in */
entry->fn_xmin = HeapTupleHeaderGetXmin(procedureTuple->t_data);
entry->fn_cmin = HeapTupleHeaderGetCmin(procedureTuple->t_data);
entry->fn_tid = procedureTuple->t_self;
entry->user_fn = user_fn;
entry->inforec = inforec;
}