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Code cleanup for assign_transaction_read_only.

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As in commit fb4c5d2798 on 2011-01-21,
this avoids spurious debug messages and allows idempotent changes at
any time.  Along the way, make assign_XactIsoLevel allow idempotent
changes even when not within a subtransaction, to be consistent with
the new coding of assign_transaction_read_only and because there's
no compelling reason to do otherwise.

Kevin Grittner, with some adjustments.
This commit is contained in:
Robert Haas 2011-01-22 20:51:32 -05:00
parent cc73c16050
commit 6f59777c65
5 changed files with 170 additions and 31 deletions
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53
src/backend/commands/variable.c
View File

@ -543,14 +543,63 @@ show_log_timezone(void)
}
/*
* SET TRANSACTION READ ONLY and SET TRANSACTION READ WRITE
*
* We allow idempotent changes (r/w -> r/w and r/o -> r/o) at any time, and
* we also always allow changes from read-write to read-only. However,
* read-only to read-write may be changed only when source == PGC_S_OVERRIDE
* (i.e. we're aborting a read only transaction and restoring the previous
* setting) or in a top-level transaction that has not yet taken an initial
* snapshot.
*/
bool
assign_transaction_read_only(bool newval, bool doit, GucSource source)
{
if (source != PGC_S_OVERRIDE && newval == false && XactReadOnly)
{
/* Can't go to r/w mode inside a r/o transaction */
if (IsSubTransaction())
{
ereport(GUC_complaint_elevel(source),
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("cannot set transaction read-write mode inside a read-only transaction")));
return false;
}
/* Top level transaction can't change to r/w after first snapshot. */
if (FirstSnapshotSet)
{
ereport(GUC_complaint_elevel(source),
(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),
errmsg("transaction read-write mode must be set before any query")));
return false;
}
/* Can't go to r/w mode while recovery is still active */
if (RecoveryInProgress())
{
ereport(GUC_complaint_elevel(source),
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("cannot set transaction read-write mode during recovery")));
return false;
}
}
return true;
}
/*
* SET TRANSACTION ISOLATION LEVEL
*
* We allow idempotent changes at any time, but otherwise this can only be
* changed from a toplevel transaction that has not yet taken a snapshot, or
* when source == PGC_S_OVERRIDE (i.e. we're aborting a transaction and
* restoring the previously set value).
*/
const char *
assign_XactIsoLevel(const char *value, bool doit, GucSource source)
{
/* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
if (source != PGC_S_OVERRIDE)
if (source != PGC_S_OVERRIDE && strcmp(value, XactIsoLevel_string) != 0)
{
if (FirstSnapshotSet)
{
@ -560,7 +609,7 @@ assign_XactIsoLevel(const char *value, bool doit, GucSource source)
return NULL;
}
/* We ignore a subtransaction setting it to the existing value. */
if (IsSubTransaction() && strcmp(value, XactIsoLevel_string) != 0)
if (IsSubTransaction())
{
ereport(GUC_complaint_elevel(source),
(errcode(ERRCODE_ACTIVE_SQL_TRANSACTION),

29
src/backend/utils/misc/guc.c
View File

@ -168,7 +168,6 @@ static bool assign_bonjour(bool newval, bool doit, GucSource source);
static bool assign_ssl(bool newval, bool doit, GucSource source);
static bool assign_stage_log_stats(bool newval, bool doit, GucSource source);
static bool assign_log_stats(bool newval, bool doit, GucSource source);
static bool assign_transaction_read_only(bool newval, bool doit, GucSource source);
static const char *assign_canonical_path(const char *newval, bool doit, GucSource source);
static const char *assign_timezone_abbreviations(const char *newval, bool doit, GucSource source);
static const char *show_archive_command(void);
@ -7843,34 +7842,6 @@ assign_log_stats(bool newval, bool doit, GucSource source)
return true;
}
static bool
assign_transaction_read_only(bool newval, bool doit, GucSource source)
{
/* Can't go to r/w mode inside a r/o transaction */
if (newval == false && XactReadOnly && IsSubTransaction())
{
ereport(GUC_complaint_elevel(source),
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("cannot set transaction read-write mode inside a read-only transaction")));
/* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
if (source != PGC_S_OVERRIDE)
return false;
}
/* Can't go to r/w mode while recovery is still active */
if (newval == false && XactReadOnly && RecoveryInProgress())
{
ereport(GUC_complaint_elevel(source),
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("cannot set transaction read-write mode during recovery")));
/* source == PGC_S_OVERRIDE means do it anyway, eg at xact abort */
if (source != PGC_S_OVERRIDE)
return false;
}
return true;
}
static const char *
assign_canonical_path(const char *newval, bool doit, GucSource source)
{

2
src/include/commands/variable.h
View File

@ -21,6 +21,8 @@ extern const char *show_timezone(void);
extern const char *assign_log_timezone(const char *value,
bool doit, GucSource source);
extern const char *show_log_timezone(void);
extern bool assign_transaction_read_only(bool value,
bool doit, GucSource source);
extern const char *assign_XactIsoLevel(const char *value,
bool doit, GucSource source);
extern const char *show_XactIsoLevel(void);

75
src/test/regress/expected/transactions.out
View File

@ -43,6 +43,81 @@ SELECT * FROM aggtest;
-- Read-only tests
CREATE TABLE writetest (a int);
CREATE TEMPORARY TABLE temptest (a int);
BEGIN;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
a
---
(0 rows)
SET TRANSACTION READ WRITE; --fail
ERROR: transaction read-write mode must be set before any query
COMMIT;
BEGIN;
SET TRANSACTION READ ONLY; -- ok
SET TRANSACTION READ WRITE; -- ok
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
a
---
(0 rows)
SAVEPOINT x;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
a
---
(0 rows)
SET TRANSACTION READ ONLY; -- ok
SET TRANSACTION READ WRITE; --fail
ERROR: cannot set transaction read-write mode inside a read-only transaction
COMMIT;
BEGIN;
SET TRANSACTION READ WRITE; -- ok
SAVEPOINT x;
SET TRANSACTION READ WRITE; -- ok
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
a
---
(0 rows)
SET TRANSACTION READ ONLY; -- ok
SET TRANSACTION READ WRITE; --fail
ERROR: cannot set transaction read-write mode inside a read-only transaction
COMMIT;
BEGIN;
SET TRANSACTION READ WRITE; -- ok
SAVEPOINT x;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
a
---
(0 rows)
ROLLBACK TO SAVEPOINT x;
SHOW transaction_read_only; -- off
transaction_read_only
-----------------------
off
(1 row)
SAVEPOINT y;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
a
---
(0 rows)
RELEASE SAVEPOINT y;
SHOW transaction_read_only; -- off
transaction_read_only
-----------------------
off
(1 row)
COMMIT;
SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY;
DROP TABLE writetest; -- fail
ERROR: cannot execute DROP TABLE in a read-only transaction

42
src/test/regress/sql/transactions.sql
View File

@ -39,6 +39,48 @@ SELECT * FROM aggtest;
CREATE TABLE writetest (a int);
CREATE TEMPORARY TABLE temptest (a int);
BEGIN;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
SET TRANSACTION READ WRITE; --fail
COMMIT;
BEGIN;
SET TRANSACTION READ ONLY; -- ok
SET TRANSACTION READ WRITE; -- ok
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
SAVEPOINT x;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
SET TRANSACTION READ ONLY; -- ok
SET TRANSACTION READ WRITE; --fail
COMMIT;
BEGIN;
SET TRANSACTION READ WRITE; -- ok
SAVEPOINT x;
SET TRANSACTION READ WRITE; -- ok
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
SET TRANSACTION READ ONLY; -- ok
SET TRANSACTION READ WRITE; --fail
COMMIT;
BEGIN;
SET TRANSACTION READ WRITE; -- ok
SAVEPOINT x;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
ROLLBACK TO SAVEPOINT x;
SHOW transaction_read_only; -- off
SAVEPOINT y;
SET TRANSACTION READ ONLY; -- ok
SELECT * FROM writetest; -- ok
RELEASE SAVEPOINT y;
SHOW transaction_read_only; -- off
COMMIT;
SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY;
DROP TABLE writetest; -- fail