Previous commit e5de601267 modified dblink
to ensure client encoding matched the server. However the added
PQsetClientEncoding() call added significant overhead. Restore original
performance in the common case where client encoding already matches
server encoding by doing nothing in that case. Applies to all active
branches.
Issue reported and work sponsored by Zonar Systems.
SnapshotNow scans have the undesirable property that, in the face of
concurrent updates, the scan can fail to see either the old or the new
versions of the row. In many cases, we work around this by requiring
DDL operations to hold AccessExclusiveLock on the object being
modified; in some cases, the existing locking is inadequate and random
failures occur as a result. This commit doesn't change anything
related to locking, but will hopefully pave the way to allowing lock
strength reductions in the future.
The major issue has held us back from making this change in the past
is that taking an MVCC snapshot is significantly more expensive than
using a static special snapshot such as SnapshotNow. However, testing
of various worst-case scenarios reveals that this problem is not
severe except under fairly extreme workloads. To mitigate those
problems, we avoid retaking the MVCC snapshot for each new scan;
instead, we take a new snapshot only when invalidation messages have
been processed. The catcache machinery already requires that
invalidation messages be sent before releasing the related heavyweight
lock; else other backends might rely on locally-cached data rather
than scanning the catalog at all. Thus, making snapshot reuse
dependent on the same guarantees shouldn't break anything that wasn't
already subtly broken.
Patch by me. Review by Michael Paquier and Andres Freund.
If the remote database's settings of these GUCs are different from ours,
ambiguous datetime values may be read incorrectly. To fix, temporarily
adopt the remote server's settings while we ingest a query result.
This is not a complete fix, since it doesn't do anything about ambiguous
values in commands sent to the remote server; but there seems little we
can do about that end of it given dblink's entirely textual API for
transmitted commands.
Back-patch to 9.2. The hazard exists in all versions, but this patch
would need more work to apply before 9.2. Given the lack of field
complaints about this issue, it doesn't seem worth the effort at present.
Daniel Farina and Tom Lane
dblink now has its own validator function dblink_fdw_validator(), which is
better than the core function postgresql_fdw_validator() because it gets
the list of legal options from libpq instead of having a hard-wired list.
Make the dblink extension module provide a standard foreign data wrapper
dblink_fdw that encapsulates use of this validator, and recommend use of
that wrapper instead of making up wrappers on the fly.
Unfortunately, because ad-hoc wrappers *were* recommended practice
previously, it's not clear when we can get rid of postgresql_fdw_validator
without causing upgrade problems. But this is a step in the right
direction.
Shigeru Hanada, reviewed by KaiGai Kohei
This reduces unnecessary exposure of other headers through htup.h, which
is very widely included by many files.
I have chosen to move the function prototypes to the new file as well,
because that means htup.h no longer needs to include tupdesc.h. In
itself this doesn't have much effect in indirect inclusion of tupdesc.h
throughout the tree, because it's also required by execnodes.h; but it's
something to explore in the future, and it seemed best to do the htup.h
change now while I'm busy with it.
After taking awhile to digest the row-processor feature that was added to
libpq in commit 92785dac2e, we've concluded
it is over-complicated and too hard to use. Leave the core infrastructure
changes in place (that is, there's still a row processor function inside
libpq), but remove the exposed API pieces, and instead provide a "single
row" mode switch that causes PQgetResult to return one row at a time in
separate PGresult objects.
This approach incurs more overhead than proper use of a row processor
callback would, since construction of a PGresult per row adds extra cycles.
However, it is far easier to use and harder to break. The single-row mode
still affords applications the primary benefit that the row processor API
was meant to provide, namely not having to accumulate large result sets in
memory before processing them. Preliminary testing suggests that we can
probably buy back most of the extra cycles by micro-optimizing construction
of the extra results, but that task will be left for another day.
Marko Kreen
This patch provides a test case for libpq's row processor API.
contrib/dblink can deal with very large result sets by dumping them into
a tuplestore (which can spill to disk) --- but until now, the intermediate
storage of the query result in a PGresult meant memory bloat for any large
result. Now we use a row processor to convert the data to tuple form and
dump it directly into the tuplestore.
A limitation is that this only works for plain dblink() queries, not
dblink_send_query() followed by dblink_get_result(). In the latter
case we don't know the desired tuple rowtype soon enough. While hack
solutions to that are possible, a different user-level API would
probably be a better answer.
Kyotaro Horiguchi, reviewed by Marko Kreen and Tom Lane
dblink_exec leaked temporary database connections if any error occurred
after connection setup, for example
SELECT dblink_exec('...connect string...', 'select 1/0');
Add a PG_TRY block to ensure PQfinish gets done when it is needed.
(dblink_record_internal is on the hairy edge of needing similar treatment,
but seems not to be actively broken at the moment.)
Also, in 9.0 and up, only one of the three functions using tuplestore
return mode was properly checking that the query context would allow
a tuplestore result.
Noted while reviewing dblink patch. Back-patch to all supported branches.
The DBLINK_GET_CONN and DBLINK_GET_NAMED_CONN macros did not set the
surrounding function's conname variable, causing errors to be incorrectly
reported as having occurred on the "unnamed" connection in some cases.
This bug was actually visible in two cases in the regression tests,
but apparently whoever added those cases wasn't paying attention.
Noted by Kyotaro Horiguchi, though this is different from his proposed
patch.
Back-patch to 8.4; 8.3 does not have the same type of error reporting
so the patch is not relevant.
There may be some other places where we should use errdetail_internal,
but they'll have to be evaluated case-by-case. This commit just hits
a bunch of places where invoking gettext is obviously a waste of cycles.
This eliminates the need for inefficient implementions of this
functionality in both contrib/dblink and contrib/tablefunc, so remove
them. The upcoming patch implementing an in-core format() function
will also require this functionality.
In passing, add some regression tests.
dblink_build_sql_insert() and related functions. Now the column numbers
are treated as logical not physical column numbers. This will provide saner
behavior in the presence of dropped columns; furthermore, if we ever get
around to allowing rearrangement of logical column ordering, the original
definition would become nearly untenable from a usability standpoint.
Per recent discussion of dblink's handling of dropped columns.
Not back-patched for fear of breaking existing applications.
columns correctly. In passing, get rid of some dead logic in the
underlying get_sql_insert() etc functions --- there is no caller that
will pass null value-arrays to them.
Per bug report from Robert Voinea.
dblink_build_sql_insert() and related functions. In particular, be sure to
reject references to dropped and out-of-range column numbers. The numbers
are still interpreted as physical column numbers, though, for backward
compatibility.
This patch replaces Joe's patch of 2010-02-03, which handled only some aspects
of the problem.
lock the target relation just once per SQL function call. The original coding
obtained and released lock several times per call. Aside from saving a
not-insignificant number of cycles, this eliminates possible race conditions
if someone tries to modify the relation's schema concurrently. Also
centralize locking and permission-checking logic.
Problem noted while investigating a trouble report from Robert Voinea --- his
problem is still to be fixed, though.
The purpose of this change is to eliminate the need for every caller
of SearchSysCache, SearchSysCacheCopy, SearchSysCacheExists,
GetSysCacheOid, and SearchSysCacheList to know the maximum number
of allowable keys for a syscache entry (currently 4). This will
make it far easier to increase the maximum number of keys in a
future release should we choose to do so, and it makes the code
shorter, too.
Design and review by Tom Lane.
exceed the total number of non-dropped source table fields for
dblink_build_sql_*(). Addresses bug report from Rushabh Lathia.
Backpatch all the way to the 7.3 branch.
(SFRM_Materialize mode) to return tuples. Since we don't return from the
dblink function in tuplestore mode, release the PGresult with a PG_CATCH
block on error. Also rearrange to share the same code to materialize the
tuplestore. Patch by Takahiro Itagaki.
PL/pgSQL function within an exception handler. Make sure we use the right
resource owner when we create the tuplestore to hold returned tuples.
Simplify tuplestore API so that the caller doesn't need to be in the right
memory context when calling tuplestore_put* functions. tuplestore.c
automatically switches to the memory context used when the tuplestore was
created. Tuplesort was already modified like this earlier. This patch also
removes the now useless MemoryContextSwitch calls from callers.
Report by Aleksei on pgsql-bugs on Dec 22 2009. Backpatch to 8.1, like
the previous patch that broke this.
dblink generates orphaned connections when called with a connection string,
fail_on_error = true, and an ERROR occurs. Discovery and patch by
Tatsuhito Kasahara. Introduced in 8.4.
Adds the ability to retrieve async notifications using dblink,
via the addition of the function dblink_get_notify(). Original patch
by Marcus Kempe, suggestions by Tom Lane and Alvaro Herrera, patch
review and adjustments by Joe Conway.
create an ABI break between 8.3 and 8.4. It is still just a wrapper around
the built-in current_query() function, but at a different implementation
level. Per my proposal.
Note: this change doesn't break 8.4beta installations, since their
SQL-language definition of the function still works fine.
while we're at it per request by Tom Lane. Specifically, don't try to
perform dblink_send_query() via dblink_record_internal() -- it was
inappropriate and ugly.
Bruce Momjian