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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
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@ -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),