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Some mop-up work for savepoints (nested transactions). Store a small

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number of active subtransaction XIDs in each backend's PGPROC entry,
and use this to avoid expensive probes into pg_subtrans during
TransactionIdIsInProgress.  Extend EOXactCallback API to allow add-on
modules to get control at subxact start/end.  (This is deliberately
not compatible with the former API, since any uses of that API probably
need manual review anyway.)  Add basic reference documentation for
SAVEPOINT and related commands.  Minor other cleanups to check off some
of the open issues for subtransactions.
Alvaro Herrera and Tom Lane.
This commit is contained in:
Tom Lane
2004-08-01 17:32:22 +00:00
parent 9d9cdf82a4
commit efcaf1e868
23 changed files with 1103 additions and 330 deletions
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41
src/include/access/htup.h
View File

@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/htup.h,v 1.67 2004/07/11 18:01:45 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/htup.h,v 1.68 2004/08/01 17:32:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -68,34 +68,17 @@
* object ID (if HEAP_HASOID is set in t_infomask)
* user data fields
*
* We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac
* in just three physical fields. Xmin is always really stored, but
* Cmin and Xmax share a field, as do Cmax and Xvac. This works because
* we know that there are only a limited number of states that a tuple can
* be in, and that Cmin and Cmax are only interesting for the lifetime of
* the inserting and deleting transactions respectively. We have the
* following possible states of a tuple:
* We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in four
* physical fields. Xmin, Cmin and Xmax are always really stored, but
* Cmax and Xvac share a field. This works because we know that there are
* only a limited number of states that a tuple can be in, and that Cmax
* is only interesting for the lifetime of the deleting transaction.
* This assumes that VACUUM FULL never tries to move a tuple whose Cmax
* is still interesting (ie, delete-in-progress).
*
* XMIN CMIN XMAX CMAX XVAC
*
* NEW (never deleted, not moved by vacuum):
* valid valid invalid invalid invalid
*
* DELETED BY CREATING XACT:
* valid valid = XMIN valid invalid
*
* DELETED BY OTHER XACT:
* valid unneeded valid valid invalid
*
* MOVED BY VACUUM FULL:
* valid unneeded maybe-valid unneeded valid
*
* This assumes that VACUUM FULL never tries to move a tuple whose Cmin or
* Cmax is still interesting (ie, insert-in-progress or delete-in-progress).
*
* This table shows that if we use an infomask bit to handle the case
* XMAX=XMIN specially, we never need to store Cmin and Xmax at the same
* time. Nor do we need to store Cmax and Xvac at the same time.
* Note that in 7.3 and 7.4 a similar idea was applied to Xmax and Cmin.
* However, with the advent of subtransactions, a tuple may need both Xmax
* and Cmin simultaneously, so this is no longer possible.
*
* Following the fixed header fields, the nulls bitmap is stored (beginning
* at t_bits). The bitmap is *not* stored if t_infomask shows that there
@@ -416,7 +399,7 @@ typedef HeapTupleData *HeapTuple;
* WAL record definitions for heapam.c's WAL operations
*
* XLOG allows to store some information in high 4 bits of log
* record xl_info field
* record xl_info field. We use 3 for opcode and one for init bit.
*/
#define XLOG_HEAP_INSERT 0x00
#define XLOG_HEAP_DELETE 0x10

19
src/include/access/xact.h
View File

@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.68 2004/07/31 07:39:19 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.69 2004/08/01 17:32:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -42,9 +42,18 @@ extern bool DefaultXactReadOnly;
extern bool XactReadOnly;
/*
* end-of-transaction cleanup callbacks for dynamically loaded modules
* start- and end-of-transaction callbacks for dynamically loaded modules
*/
typedef void (*EOXactCallback) (bool isCommit, void *arg);
typedef enum
{
XACT_EVENT_ABORT,
XACT_EVENT_COMMIT,
XACT_EVENT_START_SUB,
XACT_EVENT_ABORT_SUB,
XACT_EVENT_COMMIT_SUB
} XactEvent;
typedef void (*XactCallback) (XactEvent event, TransactionId parentXid, void *arg);
/* ----------------
@@ -118,8 +127,8 @@ extern void AbortOutOfAnyTransaction(void);
extern void PreventTransactionChain(void *stmtNode, const char *stmtType);
extern void RequireTransactionChain(void *stmtNode, const char *stmtType);
extern bool IsInTransactionChain(void *stmtNode);
extern void RegisterEOXactCallback(EOXactCallback callback, void *arg);
extern void UnregisterEOXactCallback(EOXactCallback callback, void *arg);
extern void RegisterXactCallback(XactCallback callback, void *arg);
extern void UnregisterXactCallback(XactCallback callback, void *arg);
extern void RecordTransactionCommit(void);