1 Commits (b1bfb28b586a319052d96dd4dfd40a05505ea6ed)

Author	SHA1	Message	Date
Alvaro Herrera	0ac5ad5134	Improve concurrency of foreign key locking ... This patch introduces two additional lock modes for tuples: "SELECT FOR KEY SHARE" and "SELECT FOR NO KEY UPDATE". These don't block each other, in contrast with already existing "SELECT FOR SHARE" and "SELECT FOR UPDATE". UPDATE commands that do not modify the values stored in the columns that are part of the key of the tuple now grab a SELECT FOR NO KEY UPDATE lock on the tuple, allowing them to proceed concurrently with tuple locks of the FOR KEY SHARE variety. Foreign key triggers now use FOR KEY SHARE instead of FOR SHARE; this means the concurrency improvement applies to them, which is the whole point of this patch. The added tuple lock semantics require some rejiggering of the multixact module, so that the locking level that each transaction is holding can be stored alongside its Xid. Also, multixacts now need to persist across server restarts and crashes, because they can now represent not only tuple locks, but also tuple updates. This means we need more careful tracking of lifetime of pg_multixact SLRU files; since they now persist longer, we require more infrastructure to figure out when they can be removed. pg_upgrade also needs to be careful to copy pg_multixact files over from the old server to the new, or at least part of multixact.c state, depending on the versions of the old and new servers. Tuple time qualification rules (HeapTupleSatisfies routines) need to be careful not to consider tuples with the "is multi" infomask bit set as being only locked; they might need to look up MultiXact values (i.e. possibly do pg_multixact I/O) to find out the Xid that updated a tuple, whereas they previously were assured to only use information readily available from the tuple header. This is considered acceptable, because the extra I/O would involve cases that would previously cause some commands to block waiting for concurrent transactions to finish. Another important change is the fact that locking tuples that have previously been updated causes the future versions to be marked as locked, too; this is essential for correctness of foreign key checks. This causes additional WAL-logging, also (there was previously a single WAL record for a locked tuple; now there are as many as updated copies of the tuple there exist.) With all this in place, contention related to tuples being checked by foreign key rules should be much reduced. As a bonus, the old behavior that a subtransaction grabbing a stronger tuple lock than the parent (sub)transaction held on a given tuple and later aborting caused the weaker lock to be lost, has been fixed. Many new spec files were added for isolation tester framework, to ensure overall behavior is sane. There's probably room for several more tests. There were several reviewers of this patch; in particular, Noah Misch and Andres Freund spent considerable time in it. Original idea for the patch came from Simon Riggs, after a problem report by Joel Jacobson. Most code is from me, with contributions from Marti Raudsepp, Alexander Shulgin, Noah Misch and Andres Freund. This patch was discussed in several pgsql-hackers threads; the most important start at the following message-ids: AANLkTimo9XVcEzfiBR-ut3KVNDkjm2Vxh+t8kAmWjPuv@mail.gmail.com 1290721684-sup-3951@alvh.no-ip.org 1294953201-sup-2099@alvh.no-ip.org 1320343602-sup-2290@alvh.no-ip.org 1339690386-sup-8927@alvh.no-ip.org 4FE5FF020200002500048A3D@gw.wicourts.gov 4FEAB90A0200002500048B7D@gw.wicourts.gov	13 years ago
Tom Lane	458857cc9d	Throw a useful error message if an extension script file is fed to psql. ... We have seen one too many reports of people trying to use 9.1 extension files in the old-fashioned way of sourcing them in psql. Not only does that usually not work (due to failure to substitute for MODULE_PATHNAME and/or @extschema@), but if it did work they'd get a collection of loose objects not an extension. To prevent this, insert an \echo ... \quit line that prints a suitable error message into each extension script file, and teach commands/extension.c to ignore lines starting with \echo. That should not only prevent any adverse consequences of loading a script file the wrong way, but make it crystal clear to users that they need to do it differently now. Tom Lane, following an idea of Andrew Dunstan's. Back-patch into 9.1 ... there is not going to be much value in this if we wait till 9.2.	14 years ago
Tom Lane	029fac2264	Avoid use of CREATE OR REPLACE FUNCTION in extension installation files. ... It was never terribly consistent to use OR REPLACE (because of the lack of comparable functionality for data types, operators, etc), and experimentation shows that it's now positively pernicious in the extension world. We really want a failure to occur if there are any conflicts, else it's unclear what the extension-ownership state of the conflicted object ought to be. Most of the time, CREATE EXTENSION will fail anyway because of conflicts on other object types, but an extension defining only functions can succeed, with bad results.	15 years ago
Tom Lane	629b3af27d	Convert contrib modules to use the extension facility. ... This isn't fully tested as yet, in particular I'm not sure that the "foo--unpackaged--1.0.sql" scripts are OK. But it's time to get some buildfarm cycles on it. sepgsql is not converted to an extension, mainly because it seems to require a very nonstandard installation process. Dimitri Fontaine and Tom Lane	15 years ago
Magnus Hagander	9f2e211386	Remove cvs keywords from all files.	15 years ago
Bruce Momjian	33e2e02493	Add CVS version labels to all install/uninstall scripts.	18 years ago
Tom Lane	56f3fb3ba1	Restrict pgrowlocks function to superusers. (This might be too strict, ... but no permissions check at all is certainly no good.) Clean up usage of some deprecated APIs.	19 years ago
Tatsuo Ishii	66126f9687	Add new contrib function pgrowlocks. See README.pgrowlocks for more details.	20 years ago