In 9.3, there's no particular limit on the number of bgworkers;
instead, we just count up the number that are actually registered,
and use that to set MaxBackends. However, that approach causes
problems for Hot Standby, which needs both MaxBackends and the
size of the lock table to be the same on the standby as on the
master, yet it may not be desirable to run the same bgworkers in
both places. 9.3 handles that by failing to notice the problem,
which will probably work fine in nearly all cases anyway, but is
not theoretically sound.
A further problem with simply counting the number of registered
workers is that new workers can't be registered without a
postmaster restart. This is inconvenient for administrators,
since bouncing the postmaster causes an interruption of service.
Moreover, there are a number of applications for background
processes where, by necessity, the background process must be
started on the fly (e.g. parallel query). While this patch
doesn't actually make it possible to register new background
workers after startup time, it's a necessary prerequisite.
Patch by me. Review by Michael Paquier.
Make it easier for readers of the FP docs to find out about possibly
truncated values.
Per complaint from Tom Duffey in message
F0E0F874-C86F-48D1-AA2A-0C5365BF5118@trillitech.com
Author: Albe Laurenz
Reviewed by: Abhijit Menon-Sen
Restore 4-byte designation for docs. Fix 9.3 doc query to properly pad
to four digits.
Backpatch to all active branches
Per suggestions from Ian Lawrence Barwick
Doing that results in a broken index entry in PDF output. We had only
a few like that, which is probably why nobody noticed before.
Standardize on putting the <term> first.
Josh Kupershmidt
Commit 13fe298ca0 changed this GUC to be
PGC_SUSET, but neglected to update the documentation to match.
While at it, edit and rearrange the text a little for clarity.
Checksums are set immediately prior to flush out of shared buffers
and checked when pages are read in again. Hint bit setting will
require full page write when block is dirtied, which causes various
infrastructure changes. Extensive comments, docs and README.
WARNING message thrown if checksum fails on non-all zeroes page;
ERROR thrown but can be disabled with ignore_checksum_failure = on.
Feature enabled by an initdb option, since transition from option off
to option on is long and complex and has not yet been implemented.
Default is not to use checksums.
Checksum used is WAL CRC-32 truncated to 16-bits.
Simon Riggs, Jeff Davis, Greg Smith
Wide input and assistance from many community members. Thank you.
This GUC allows limiting the time spent waiting to acquire any one
heavyweight lock.
In support of this, improve the recently-added timeout infrastructure
to permit efficiently enabling or disabling multiple timeouts at once.
That reduces the performance hit from turning on lock_timeout, though
it's still not zero.
Zoltán Böszörményi, reviewed by Tom Lane,
Stephen Frost, and Hari Babu
Clarify the docs explaining what commit_delay does, and add a
recommendation about a useful value for it, namely half of the single-page
fsync time reported by pg_test_fsync. This is informed by testing of
the new-in-9.3 implementation of commit_delay; in prior versions it
was far harder to arrive at a useful setting.
In passing, do some wordsmithing and markup-fixing in the same general
area.
Also, change pg_test_fsync's default time-per-test from 2 seconds to 5.
The old value was about the minimum at which the results could be taken
seriously at all, and so seems a tad optimistic as a default.
Peter Geoghegan, reviewed by Noah Misch; some additional editing by me
storage.
Have pg_upgrade use it, and enable server options fsync=off and
full_page_writes=off.
Document that users turning fsync from off to on should run initdb
--sync-only.
[ Previous commit was incorrectly applied as a git merge. ]
Rename replication_timeout to wal_sender_timeout, and add a new setting
called wal_receiver_timeout that does the same at the walreceiver side.
There was previously no timeout in walreceiver, so if the network went down,
for example, the walreceiver could take a long time to notice that the
connection was lost. Now with the two settings, both sides of a replication
connection will detect a broken connection similarly.
It is no longer necessary to manually set wal_receiver_status_interval to
a value smaller than the timeout. Both wal sender and receiver now
automatically send a "ping" message if more than 1/2 of the configured
timeout has elapsed, and it hasn't received any messages from the other end.
Amit Kapila, heavily edited by me.
Copy-editing for previous patch, plus fixing some longstanding markup
issues and oversights (like not mentioning that failures will set the
PQerrorMessage string).
This allows easily splitting configuration into many files, deployed in a
directory.
Magnus Hagander, Greg Smith, Selena Deckelmann, reviewed by Noah Misch.
Somewhere along the line, somebody decided to remove all trace of this
notation from the documentation text. It was still in the command syntax
synopses, or at least some of them, but with no indication what it meant.
This will not do, as evidenced by the confusion apparent in bug #7543;
even if the notation is now unnecessary, people will find it in legacy
SQL code and need to know what it does.
The docs claimed that this mode only waits for the standby to receive WAL
data, but actually it waits for the data to be written out to the standby's
OS; which is a pretty significant difference because it removes the risk of
crash of the walreceiver process.
Replace unix_socket_directory with unix_socket_directories, which is a list
of socket directories, and adjust postmaster's code to allow zero or more
Unix-domain sockets to be created.
This is mostly a straightforward change, but since the Unix sockets ought
to be created after the TCP/IP sockets for safety reasons (better chance
of detecting a port number conflict), AddToDataDirLockFile needs to be
fixed to support out-of-order updates of data directory lockfile lines.
That's a change that had been foreseen to be necessary someday anyway.
Honza Horak, reviewed and revised by Tom Lane
Should be limited to the maximum number of connections excluding
autovacuum workers, not including.
Add similar check for max_wal_senders, which should never be higher than
max_connections.
Instead of letting every backend participating in a group commit wait
independently, have the first one that becomes ready to flush WAL wait
for the configured delay, and let all the others wait just long enough
for that first process to complete its flush. This greatly increases
the chances of being able to configure a commit_delay setting that
actually improves performance.
As a side consequence of this change, commit_delay now affects all WAL
flushes, rather than just commits. There was some discussion on
pgsql-hackers about whether to rename the GUC to, say, wal_flush_delay,
but in the absence of consensus I am leaving it alone for now.
Peter Geoghegan, with some changes, mostly to the documentation, by me.
Rewrite description of "include_if_exists" for clarity. Add subsection
headings to make the structure of the page a little clearer. A couple
other minor improvements too.
Josh Kupershmidt and Tom Lane
Previously we attempted to throw an error or at least warning for missing
schemas, but this was done inconsistently because of implementation
restrictions (in many cases, GUC settings are applied outside transactions
so that we can't do system catalog lookups). Furthermore, there were
exceptions to the rule even in the beginning, and we'd been poking more
and more holes in it as time went on, because it turns out that there are
lots of use-cases for having some irrelevant items in a common search_path
value. It seems better to just adopt a philosophy similar to what's always
been done with Unix PATH settings, wherein nonexistent or unreadable
directories are silently ignored.
This commit also fixes the documentation to point out that schemas for
which the user lacks USAGE privilege are silently ignored. That's always
been true but was previously not documented.
This is mostly in response to Robert Haas' complaint that 9.1 started to
throw errors or warnings for missing schemas in cases where prior releases
had not. We won't adopt such a significant behavioral change in a back
branch, so something different will be needed in 9.1.
It's still non-deterministic in some sense ... but given fixed settings
and identical planning problems, it will now always choose the same plan,
so we probably shouldn't tar it with that brush. Per bug #6565 from
Guillaume Cottenceau. Back-patch to 9.0 where the behavior was fixed.
Ants Aasma's original patch to add timing information for buffer I/O
requests exposed this data at the relation level, which was judged too
costly. I've here exposed it at the database level instead.
Robert Haas
Alvaro Herrera
Fujii Masao
Peter Eisentraut
Bruce Momjian
Simon Riggs
Kevin Grittner
Tom Lane
Heikki Linnakangas
Magnus Hagander