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Issue ERROR if FREEZE mode can't be honored by COPY

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Previously non-honored FREEZE mode was ignored.  This also issues an
appropriate error message based on the cause of the failure, per
suggestion from Tom.  Additional regression test case added.
This commit is contained in:
Bruce Momjian 2013-01-26 13:33:24 -05:00
parent 7e2322dff3
commit 4deb57de7d
4 changed files with 40 additions and 31 deletions
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12
doc/src/sgml/ref/copy.sgml
View File

@ -190,18 +190,14 @@ COPY { <replaceable class="parameter">table_name</replaceable> [ ( <replaceable
would be after running the <command>VACUUM FREEZE</> command.
This is intended as a performance option for initial data loading.
Rows will be frozen only if the table being loaded has been created
in the current subtransaction, there are no cursors open and there
are no older snapshots held by this transaction. If those conditions
are not met the command will continue without error though will not
freeze rows. It is also possible in rare cases that the request
cannot be honoured for internal reasons, hence <literal>FREEZE</literal>
is more of a guideline than a hard rule.
or truncated in the current subtransaction, there are no cursors
open and there are no older snapshots held by this transaction.
</para>
<para>
Note that all other sessions will immediately be able to see the data
once it has been successfully loaded. This violates the normal rules
of MVCC visibility and by specifying this option the user acknowledges
explicitly that this is understood.
of MVCC visibility and users specifying should be aware of the
potential problems this might cause.
</para>
</listitem>
</varlistentry>

32
src/backend/commands/copy.c
View File

@ -1978,8 +1978,6 @@ CopyFrom(CopyState cstate)
* ROLLBACK TO save;
* COPY ...
*
* However this is OK since at worst we will fail to make the optimization.
*
* Also, if the target file is new-in-transaction, we assume that checking
* FSM for free space is a waste of time, even if we must use WAL because
* of archiving. This could possibly be wrong, but it's unlikely.
@ -1991,6 +1989,7 @@ CopyFrom(CopyState cstate)
* no additional work to enforce that.
*----------
*/
/* createSubid is creation check, newRelfilenodeSubid is truncation check */
if (cstate->rel->rd_createSubid != InvalidSubTransactionId ||
cstate->rel->rd_newRelfilenodeSubid != InvalidSubTransactionId)
{
@ -2006,18 +2005,27 @@ CopyFrom(CopyState cstate)
* after xact cleanup. Note that the stronger test of exactly
* which subtransaction created it is crucial for correctness
* of this optimisation.
*
* As noted above rd_newRelfilenodeSubid is not set in all cases
* where we can apply the optimization, so in those rare cases
* where we cannot honour the request we do so silently.
*/
if (cstate->freeze &&
ThereAreNoPriorRegisteredSnapshots() &&
ThereAreNoReadyPortals() &&
(cstate->rel->rd_newRelfilenodeSubid == GetCurrentSubTransactionId() ||
cstate->rel->rd_createSubid == GetCurrentSubTransactionId()))
hi_options |= HEAP_INSERT_FROZEN;
if (cstate->freeze)
{
if (!ThereAreNoPriorRegisteredSnapshots() || !ThereAreNoReadyPortals())
ereport(ERROR,
(ERRCODE_INVALID_TRANSACTION_STATE,
errmsg("cannot perform FREEZE because of prior transaction activity")));
if (cstate->rel->rd_createSubid == GetCurrentSubTransactionId() ||
cstate->rel->rd_newRelfilenodeSubid == GetCurrentSubTransactionId())
hi_options |= HEAP_INSERT_FROZEN;
else
ereport(ERROR,
(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE,
errmsg("cannot perform FREEZE because of transaction activity after table creation or truncation")));
}
}
else if (cstate->freeze)
ereport(ERROR,
(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE,
errmsg("cannot perform FREEZE because the table was not created or truncated in the current transaction")));
/*
* We need a ResultRelInfo so we can use the regular executor's

18
src/test/regress/expected/copy2.out
View File

@ -334,22 +334,20 @@ SELECT * FROM vistest;
COMMIT;
TRUNCATE vistest;
COPY vistest FROM stdin CSV FREEZE;
ERROR: cannot perform FREEZE because the table was not created or truncated in the current transaction
BEGIN;
TRUNCATE vistest;
SAVEPOINT s1;
COPY vistest FROM stdin CSV FREEZE;
ERROR: cannot perform FREEZE because of transaction activity after table creation or truncation
COMMIT;
BEGIN;
INSERT INTO vistest VALUES ('z');
SAVEPOINT s1;
TRUNCATE vistest;
ROLLBACK TO SAVEPOINT s1;
COPY vistest FROM stdin CSV FREEZE;
SELECT * FROM vistest;
a
----
p
g
z
d3
e
(5 rows)
ERROR: cannot perform FREEZE because the table was not created or truncated in the current transaction
COMMIT;
CREATE FUNCTION truncate_in_subxact() RETURNS VOID AS
$$

9
src/test/regress/sql/copy2.sql
View File

@ -234,6 +234,14 @@ p
g
\.
BEGIN;
TRUNCATE vistest;
SAVEPOINT s1;
COPY vistest FROM stdin CSV FREEZE;
m
k
\.
COMMIT;
BEGIN;
INSERT INTO vistest VALUES ('z');
SAVEPOINT s1;
TRUNCATE vistest;
@ -242,7 +250,6 @@ COPY vistest FROM stdin CSV FREEZE;
d3
e
\.
SELECT * FROM vistest;
COMMIT;
CREATE FUNCTION truncate_in_subxact() RETURNS VOID AS
$$