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Revert "Handle better implicit transaction state of pipeline mode"

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This reverts commit d77f91214fb7 on all stable branches, due to concerns
regarding the compatility side effects this could create in a minor
release.  The change still exists on HEAD.

Discussion: https://postgr.es/m/CA+TgmoZqRgeFTg4+Yf_CMRRXiHuNz1u6ZC4FvVk+rxw0RmOPnw@mail.gmail.com
Backpatch-through: 13
This commit is contained in:
Michael Paquier 2024-11-28 09:43:21 +09:00
parent c93dffd89b
commit 7668e85a40
4 changed files with 23 additions and 203 deletions
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21
doc/src/sgml/protocol.sgml
View File

@ -1070,17 +1070,16 @@ SELCT 1/0;<!-- this typo is intentional -->
<para>
If the client has not issued an explicit <command>BEGIN</command>,
then an implicit transaction block is started and each Sync ordinarily
causes an implicit <command>COMMIT</command> if the preceding step(s)
succeeded, or an implicit <command>ROLLBACK</command> if they failed.
This implicit transaction block will only be detected by the server
when the first command ends without a sync. There are a few DDL
commands (such as <command>CREATE DATABASE</command>) that cannot be
executed inside a transaction block. If one of these is executed in a
pipeline, it will fail unless it is the first command after a Sync.
Furthermore, upon success it will force an immediate commit to preserve
database consistency. Thus a Sync immediately following one of these
commands has no effect except to respond with ReadyForQuery.
then each Sync ordinarily causes an implicit <command>COMMIT</command>
if the preceding step(s) succeeded, or an
implicit <command>ROLLBACK</command> if they failed. However, there
are a few DDL commands (such as <command>CREATE DATABASE</command>)
that cannot be executed inside a transaction block. If one of
these is executed in a pipeline, it will fail unless it is the first
command in the pipeline. Furthermore, upon success it will force an
immediate commit to preserve database consistency. Thus a Sync
immediately following one of these commands has no effect except to
respond with ReadyForQuery.
</para>
<para>

13
src/backend/access/transam/xact.c
View File

@ -3603,6 +3603,16 @@ PreventInTransactionBlock(bool isTopLevel, const char *stmtType)
errmsg("%s cannot run inside a subtransaction",
stmtType)));
/*
* inside a pipeline that has started an implicit transaction?
*/
if (MyXactFlags & XACT_FLAGS_PIPELINING)
ereport(ERROR,
(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
/* translator: %s represents an SQL statement name */
errmsg("%s cannot be executed within a pipeline",
stmtType)));
/*
* inside a function call?
*/
@ -3714,6 +3724,9 @@ IsInTransactionBlock(bool isTopLevel)
if (IsSubTransaction())
return true;
if (MyXactFlags & XACT_FLAGS_PIPELINING)
return true;
if (!isTopLevel)
return true;

18
src/backend/tcop/postgres.c
View File

@ -2775,17 +2775,6 @@ start_xact_command(void)
xact_started = true;
}
else if (MyXactFlags & XACT_FLAGS_PIPELINING)
{
/*
* When the first Execute message is completed, following commands
* will be done in an implicit transaction block created via
* pipelining. The transaction state needs to be updated to an
* implicit block if we're not already in a transaction block (like
* one started by an explicit BEGIN).
*/
BeginImplicitTransactionBlock();
}
/*
* Start statement timeout if necessary. Note that this'll intentionally
@ -4971,13 +4960,6 @@ PostgresMain(const char *dbname, const char *username)
case PqMsg_Sync:
pq_getmsgend(&input_message);
/*
* If pipelining was used, we may be in an implicit
* transaction block. Close it before calling
* finish_xact_command.
*/
EndImplicitTransactionBlock();
finish_xact_command();
valgrind_report_error_query("SYNC message");
send_ready_for_query = true;

174
src/bin/pgbench/t/001_pgbench_with_server.pl
View File

@ -968,180 +968,6 @@ $node->pgbench(
}
});
# Try SET LOCAL as first pipeline command. This succeeds and the first
# command is not executed inside an implicit transaction block, causing
# a WARNING.
$node->pgbench(
'-t 1 -n -M extended',
0,
[],
[qr{WARNING: SET LOCAL can only be used in transaction blocks}],
'SET LOCAL outside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_set_local_1' => q{
\startpipeline
SET LOCAL statement_timeout='1h';
\endpipeline
}
});
# Try SET LOCAL as second pipeline command. This succeeds and the second
# command does not cause a WARNING to be generated.
$node->pgbench(
'-t 1 -n -M extended',
0,
[],
[qr{^$}],
'SET LOCAL inside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_set_local_2' => q{
\startpipeline
SELECT 1;
SET LOCAL statement_timeout='1h';
\endpipeline
}
});
# Try SET LOCAL with \syncpipeline. This succeeds and the command
# launched after the sync is outside the implicit transaction block
# of the pipeline, causing a WARNING.
$node->pgbench(
'-t 1 -n -M extended',
0,
[],
[qr{WARNING: SET LOCAL can only be used in transaction blocks}],
'SET LOCAL and \syncpipeline',
{
'001_pgbench_pipeline_set_local_3' => q{
\startpipeline
SELECT 1;
\syncpipeline
SET LOCAL statement_timeout='1h';
\endpipeline
}
});
# Try REINDEX CONCURRENTLY as first pipeline command. This succeeds
# as the first command is outside the implicit transaction block of
# a pipeline.
$node->pgbench(
'-t 1 -n -M extended',
0,
[],
[],
'REINDEX CONCURRENTLY outside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_reindex_1' => q{
\startpipeline
REINDEX TABLE CONCURRENTLY pgbench_accounts;
SELECT 1;
\endpipeline
}
});
# Try REINDEX CONCURRENTLY as second pipeline command. This fails
# as the second command is inside an implicit transaction block.
$node->pgbench(
'-t 1 -n -M extended',
2,
[],
[],
'error: REINDEX CONCURRENTLY inside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_reindex_2' => q{
\startpipeline
SELECT 1;
REINDEX TABLE CONCURRENTLY pgbench_accounts;
\endpipeline
}
});
# Try VACUUM as first pipeline command. Like REINDEX CONCURRENTLY, this
# succeeds as this is outside the implicit transaction block of a pipeline.
$node->pgbench(
'-t 1 -n -M extended',
0,
[],
[],
'VACUUM outside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_vacuum_1' => q{
\startpipeline
VACUUM pgbench_accounts;
\endpipeline
}
});
# Try VACUUM as second pipeline command. This fails, as the second command
# of a pipeline is inside an implicit transaction block.
$node->pgbench(
'-t 1 -n -M extended',
2,
[],
[],
'error: VACUUM inside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_vacuum_2' => q{
\startpipeline
SELECT 1;
VACUUM pgbench_accounts;
\endpipeline
}
});
# Try subtransactions in a pipeline. These are forbidden in implicit
# transaction blocks.
$node->pgbench(
'-t 1 -n -M extended',
2,
[],
[],
'error: subtransactions not allowed in pipeline',
{
'001_pgbench_pipeline_subtrans' => q{
\startpipeline
SAVEPOINT a;
SELECT 1;
ROLLBACK TO SAVEPOINT a;
SELECT 2;
\endpipeline
}
});
# Try LOCK TABLE as first pipeline command. This fails as LOCK is outside
# an implicit transaction block.
$node->pgbench(
'-t 1 -n -M extended',
2,
[],
[],
'error: LOCK TABLE outside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_lock_1' => q{
\startpipeline
LOCK pgbench_accounts;
SELECT 1;
\endpipeline
}
});
# Try LOCK TABLE as second pipeline command. This succeeds as LOCK is inside
# an implicit transaction block.
$node->pgbench(
'-t 1 -n -M extended',
0,
[],
[],
'LOCK TABLE inside implicit transaction block of pipeline',
{
'001_pgbench_pipeline_lock_2' => q{
\startpipeline
SELECT 1;
LOCK pgbench_accounts;
\endpipeline
}
});
# Working \startpipeline in prepared query mode with serializable
$node->pgbench(
'-c4 -t 10 -n -M prepared',