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Update xact.c comments for clarity.

This commit is contained in:
Bruce Momjian 2002-11-13 03:12:05 +00:00
parent 34529aeb64
commit 63e9734542
2 changed files with 102 additions and 114 deletions
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59
src/backend/access/transam/xact.c
View File

@ -8,13 +8,13 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.137 2002/11/11 22:19:20 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.138 2002/11/13 03:12:05 momjian Exp $
*
* NOTES
* Transaction aborts can now occur two ways:
*
* 1) system dies from some internal cause (Assert, etc..)
* 2) user types abort
* 1) system dies from some internal cause (syntax error, etc..)
* 2) user types ABORT
*
* These two cases used to be treated identically, but now
* we need to distinguish them. Why? consider the following
@ -30,8 +30,8 @@
* In case 1, we want to abort the transaction and return to the
* default state. In case 2, there may be more commands coming
* our way which are part of the same transaction block and we have
* to ignore these commands until we see an END transaction.
* (or an ABORT! --djm)
* to ignore these commands until we see a COMMIT transaction or
* ROLLBACK.
*
* Internal aborts are now handled by AbortTransactionBlock(), just as
* they always have been, and user aborts are now handled by
@ -52,14 +52,6 @@
* TransactionCommandContext until this point.
*
* NOTES
* This file is an attempt at a redesign of the upper layer
* of the V1 transaction system which was too poorly thought
* out to describe. This new system hopes to be both simpler
* in design, simpler to extend and needs to contain added
* functionality to solve problems beyond the scope of the V1
* system. (In particuler, communication of transaction
* information between parallel backends has to be supported)
*
* The essential aspects of the transaction system are:
*
* o transaction id generation
@ -69,7 +61,7 @@
* o lock cleanup
*
* Hence, the functional division of the transaction code is
* based on what of the above things need to be done during
* based on which of the above things need to be done during
* a start/commit/abort transaction. For instance, the
* routine AtCommit_Memory() takes care of all the memory
* cleanup stuff done at commit time.
@ -99,17 +91,17 @@
* CommitTransactionBlock
* AbortTransactionBlock
*
* These are invoked only in responce to a user "BEGIN", "END",
* or "ABORT" command. The tricky part about these functions
* These are invoked only in responce to a user "BEGIN WORK", "COMMIT",
* or "ROLLBACK" command. The tricky part about these functions
* is that they are called within the postgres main loop, in between
* the StartTransactionCommand() and CommitTransactionCommand().
*
* For example, consider the following sequence of user commands:
*
* 1) begin
* 2) retrieve (foo.all)
* 3) append foo (bar = baz)
* 4) end
* 2) select * from foo
* 3) insert into foo (bar = baz)
* 4) commit
*
* in the main processing loop, this results in the following
* transaction sequence:
@ -120,15 +112,15 @@
* \ CommitTransactionCommand();
*
* / StartTransactionCommand();
* 2) < ProcessQuery(); << retrieve (foo.all)
* 2) < ProcessQuery(); << select * from foo
* \ CommitTransactionCommand();
*
* / StartTransactionCommand();
* 3) < ProcessQuery(); << append foo (bar = baz)
* 3) < ProcessQuery(); << insert into foo (bar = baz)
* \ CommitTransactionCommand();
*
* / StartTransactionCommand();
* 4) / ProcessUtility(); << end
* 4) / ProcessUtility(); << commit
* \ CommitTransactionBlock();
* \ CommitTransactionCommand();
*
@ -139,19 +131,14 @@
* outside these calls they need to do normal start/commit
* processing.
*
* Furthermore, suppose the "retrieve (foo.all)" caused an abort
* Furthermore, suppose the "select * from foo" caused an abort
* condition. We would then want to abort the transaction and
* ignore all subsequent commands up to the "end".
* ignore all subsequent commands up to the "commit".
* -cim 3/23/90
*
*-------------------------------------------------------------------------
*/
/*
* Large object clean up added in CommitTransaction() to prevent buffer leaks.
* [PA, 7/17/98]
* [PA] is Pascal André <andre@via.ecp.fr>
*/
#include "postgres.h"
#include <unistd.h>
@ -201,9 +188,8 @@ static void CommitTransaction(void);
static void RecordTransactionAbort(void);
static void StartTransaction(void);
/* ----------------
/*
* global variables holding the current transaction state.
* ----------------
*/
static TransactionStateData CurrentTransactionStateData = {
0, /* transaction id */
@ -211,7 +197,7 @@ static TransactionStateData CurrentTransactionStateData = {
0, /* scan command id */
0x0, /* start time */
TRANS_DEFAULT, /* transaction state */
TBLOCK_DEFAULT /* transaction block state */
TBLOCK_DEFAULT /* transaction block state of client queries */
};
TransactionState CurrentTransactionState = &CurrentTransactionStateData;
@ -853,7 +839,6 @@ AtCleanup_Memory(void)
/* --------------------------------
* StartTransaction
*
* --------------------------------
*/
static void
@ -930,7 +915,6 @@ CurrentXactInProgress(void)
/* --------------------------------
* CommitTransaction
*
* --------------------------------
*/
static void
@ -1051,7 +1035,6 @@ CommitTransaction(void)
/* --------------------------------
* AbortTransaction
*
* --------------------------------
*/
static void
@ -1158,7 +1141,6 @@ AbortTransaction(void)
/* --------------------------------
* CleanupTransaction
*
* --------------------------------
*/
static void
@ -1730,6 +1712,11 @@ IsTransactionBlock(void)
return false;
}
/*
* XLOG support routines
*/
void
xact_redo(XLogRecPtr lsn, XLogRecord *record)
{

15
src/include/access/xact.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: xact.h,v 1.46 2002/10/21 22:06:20 tgl Exp $
* $Id: xact.h,v 1.47 2002/11/13 03:12:05 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@ -46,9 +46,11 @@ typedef struct TransactionStateData
typedef TransactionStateData *TransactionState;
/* ----------------
* transaction states
* ----------------
/*
* transaction states - transaction state from server perspective
*
* Syntax error could cause transaction to abort, but client code thinks
* it is still in a transaction, so we have to wait for COMMIT/ROLLBACK.
*/
#define TRANS_DEFAULT 0
#define TRANS_START 1
@ -56,9 +58,8 @@ typedef TransactionStateData *TransactionState;
#define TRANS_COMMIT 3
#define TRANS_ABORT 4
/* ----------------
* transaction block states
* ----------------
/*
* transaction block states - transaction state of client queries
*/
#define TBLOCK_DEFAULT 0
#define TBLOCK_BEGIN 1