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2014-10-18Allow setting effective_io_concurrency even on unsupported systemsPeter Eisentraut
This matches the behavior of other parameters that are unsupported on some systems (e.g., ssl). Also document the default value.
2014-10-16Support timezone abbreviations that sometimes change.Tom Lane
Up to now, PG has assumed that any given timezone abbreviation (such as "EDT") represents a constant GMT offset in the usage of any particular region; we had a way to configure what that offset was, but not for it to be changeable over time. But, as with most things horological, this view of the world is too simplistic: there are numerous regions that have at one time or another switched to a different GMT offset but kept using the same timezone abbreviation. Almost the entire Russian Federation did that a few years ago, and later this month they're going to do it again. And there are similar examples all over the world. To cope with this, invent the notion of a "dynamic timezone abbreviation", which is one that is referenced to a particular underlying timezone (as defined in the IANA timezone database) and means whatever it currently means in that zone. For zones that use or have used daylight-savings time, the standard and DST abbreviations continue to have the property that you can specify standard or DST time and get that time offset whether or not DST was theoretically in effect at the time. However, the abbreviations mean what they meant at the time in question (or most recently before that time) rather than being absolutely fixed. The standard abbreviation-list files have been changed to use this behavior for abbreviations that have actually varied in meaning since 1970. The old simple-numeric definitions are kept for abbreviations that have not changed, since they are a bit faster to resolve. While this is clearly a new feature, it seems necessary to back-patch it into all active branches, because otherwise use of Russian zone abbreviations is going to become even more problematic than it already was. This change supersedes the changes in commit 513d06ded et al to modify the fixed meanings of the Russian abbreviations; since we've not shipped that yet, this will avoid an undesirably incompatible (not to mention incorrect) change in behavior for timestamps between 2011 and 2014. This patch makes some cosmetic changes in ecpglib to keep its usage of datetime lookup tables as similar as possible to the backend code, but doesn't do anything about the increasingly obsolete set of timezone abbreviation definitions that are hard-wired into ecpglib. Whatever we do about that will likely not be appropriate material for back-patching. Also, a potential free() of a garbage pointer after an out-of-memory failure in ecpglib has been fixed. This patch also fixes pre-existing bugs in DetermineTimeZoneOffset() that caused it to produce unexpected results near a timezone transition, if both the "before" and "after" states are marked as standard time. We'd only ever thought about or tested transitions between standard and DST time, but that's not what's happening when a zone simply redefines their base GMT offset. In passing, update the SGML documentation to refer to the Olson/zoneinfo/ zic timezone database as the "IANA" database, since it's now being maintained under the auspices of IANA.
2014-10-13Consistently use NULL for invalid GUC unit stringsBruce Momjian
Patch by Euler Taveira
2014-10-04Update time zone data files to tzdata release 2014h.Tom Lane
Most zones in the Russian Federation are subtracting one or two hours as of 2014-10-26. Update the meanings of the abbreviations IRKT, KRAT, MAGT, MSK, NOVT, OMST, SAKT, VLAT, YAKT, YEKT to match. The IANA timezone database has adopted abbreviations of the form AxST/AxDT for all Australian time zones, reflecting what they believe to be current majority practice Down Under. These names do not conflict with usage elsewhere (other than ACST for Acre Summer Time, which has been in disuse since 1994). Accordingly, adopt these names into our "Default" timezone abbreviation set. The "Australia" abbreviation set now contains only CST,EAST,EST,SAST,SAT,WST, all of which are thought to be mostly historical usage. Note that SAST has also been changed to be South Africa Standard Time in the "Default" abbreviation set. Add zone abbreviations SRET (Asia/Srednekolymsk) and XJT (Asia/Urumqi), and use WSST/WSDT for western Samoa. Also a DST law change in the Turks & Caicos Islands (America/Grand_Turk), and numerous corrections for historical time zone data.
2014-10-01Remove num_xloginsert_locks GUC, replace with a #defineHeikki Linnakangas
I left the GUC in place for the beta period, so that people could experiment with different values. No-one's come up with any data that a different value would be better under some circumstances, so rather than try to document to users what the GUC, let's just hard-code the current value, 8.
2014-09-19Row-Level Security Policies (RLS)Stephen Frost
Building on the updatable security-barrier views work, add the ability to define policies on tables to limit the set of rows which are returned from a query and which are allowed to be added to a table. Expressions defined by the policy for filtering are added to the security barrier quals of the query, while expressions defined to check records being added to a table are added to the with-check options of the query. New top-level commands are CREATE/ALTER/DROP POLICY and are controlled by the table owner. Row Security is able to be enabled and disabled by the owner on a per-table basis using ALTER TABLE .. ENABLE/DISABLE ROW SECURITY. Per discussion, ROW SECURITY is disabled on tables by default and must be enabled for policies on the table to be used. If no policies exist on a table with ROW SECURITY enabled, a default-deny policy is used and no records will be visible. By default, row security is applied at all times except for the table owner and the superuser. A new GUC, row_security, is added which can be set to ON, OFF, or FORCE. When set to FORCE, row security will be applied even for the table owner and superusers. When set to OFF, row security will be disabled when allowed and an error will be thrown if the user does not have rights to bypass row security. Per discussion, pg_dump sets row_security = OFF by default to ensure that exports and backups will have all data in the table or will error if there are insufficient privileges to bypass row security. A new option has been added to pg_dump, --enable-row-security, to ask pg_dump to export with row security enabled. A new role capability, BYPASSRLS, which can only be set by the superuser, is added to allow other users to be able to bypass row security using row_security = OFF. Many thanks to the various individuals who have helped with the design, particularly Robert Haas for his feedback. Authors include Craig Ringer, KaiGai Kohei, Adam Brightwell, Dean Rasheed, with additional changes and rework by me. Reviewers have included all of the above, Greg Smith, Jeff McCormick, and Robert Haas.
2014-09-13Invent PGC_SU_BACKEND and mark log_connections/log_disconnections that way.Tom Lane
This new GUC context option allows GUC parameters to have the combined properties of PGC_BACKEND and PGC_SUSET, ie, they don't change after session start and non-superusers can't change them. This is a more appropriate choice for log_connections and log_disconnections than their previous context of PGC_BACKEND, because we don't want non-superusers to be able to affect whether their sessions get logged. Note: the behavior for log_connections is still a bit odd, in that when a superuser attempts to set it from PGOPTIONS, the setting takes effect but it's too late to enable or suppress connection startup logging. It's debatable whether that's worth fixing, and in any case there is a reasonable argument for PGC_SU_BACKEND to exist. In passing, re-pgindent the files touched by this commit. Fujii Masao, reviewed by Joe Conway and Amit Kapila
2014-09-13Add GUC to enable logging of replication commands.Fujii Masao
Previously replication commands like IDENTIFY_COMMAND were not logged even when log_statements is set to all. Some users who want to audit all types of statements were not satisfied with this situation. To address the problem, this commit adds new GUC log_replication_commands. If it's enabled, all replication commands are logged in the server log. There are many ways to allow us to enable that logging. For example, we can extend log_statement so that replication commands are logged when it's set to all. But per discussion in the community, we reached the consensus to add separate GUC for that. Reviewed by Ian Barwick, Robert Haas and Heikki Linnakangas.
2014-09-02Support ALTER SYSTEM RESET command.Fujii Masao
This patch allows us to execute ALTER SYSTEM RESET command to remove the configuration entry from postgresql.auto.conf. Vik Fearing, reviewed by Amit Kapila and me.
2014-08-29Assorted message improvementsPeter Eisentraut
2014-08-20Use comma+space as the separator in the default search_path.Heikki Linnakangas
While the space is optional, it seems nicer to be consistent with what you get if you do "SET search_path=...". SET always normalizes the separator to be comma+space. Christoph Martin
2014-08-12Change first call of ProcessConfigFile so as to process only data_directory.Fujii Masao
When both postgresql.conf and postgresql.auto.conf have their own entry of the same parameter, PostgreSQL uses the entry in postgresql.auto.conf because it appears last in the configuration scan. IOW, the other entries which appear earlier are ignored. But, previously, ProcessConfigFile() detected the invalid settings of even those unused entries and emitted the error messages complaining about them, at postmaster startup. Complaining about the entries to ignore is basically useless. This problem happened because ProcessConfigFile() was called twice at postmaster startup and the first call read only postgresql.conf. That is, the first call could check the entry which might be ignored eventually by the second call which read both postgresql.conf and postgresql.auto.conf. To work around the problem, this commit changes ProcessConfigFile so that its first call processes only data_directory and the second one does all the entries. It's OK to process data_directory in the first call because it's ensured that data_directory doesn't exist in postgresql.auto.conf. Back-patch to 9.4 where postgresql.auto.conf was added. Patch by me. Review by Amit Kapila
2014-08-11Break out OpenSSL-specific code to separate files.Heikki Linnakangas
This refactoring is in preparation for adding support for other SSL implementations, with no user-visible effects. There are now two #defines, USE_OPENSSL which is defined when building with OpenSSL, and USE_SSL which is defined when building with any SSL implementation. Currently, OpenSSL is the only implementation so the two #defines go together, but USE_SSL is supposed to be used for implementation-independent code. The libpq SSL code is changed to use a custom BIO, which does all the raw I/O, like we've been doing in the backend for a long time. That makes it possible to use MSG_NOSIGNAL to block SIGPIPE when using SSL, which avoids a couple of syscall for each send(). Probably doesn't make much performance difference in practice - the SSL encryption is expensive enough to mask the effect - but it was a natural result of this refactoring. Based on a patch by Martijn van Oosterhout from 2006. Briefly reviewed by Alvaro Herrera, Andreas Karlsson, Jeff Janes.
2014-08-06Change ParseConfigFp() so that it doesn't process unused entry of each ↵Fujii Masao
parameter. When more than one setting entries of same parameter exist in the configuration file, PostgreSQL uses only entry appearing last in configuration file scan. Since the other entries are not used, ParseConfigFp() doesn't need to process them, but previously it did that. This problematic behavior caused the configuration file scan to detect invalid settings of unused entries (e.g., existence of multiple entries of PGC_POSTMASTER parameter) and log the messages complaining about them. This commit changes the configuration file scan so that it processes only last entry of each parameter. Note that when multiple entries of same parameter exist both in postgresql.conf and postgresql.auto.conf, unused entries in postgresql.conf are still processed only at postmaster startup. The problem has existed since old version, but a user is more likely to encounter it since 9.4 where ALTER SYSTEM command was introduced. So back-patch to 9.4. Amit Kapila, slightly modified by me. Per report from Christoph Berg.
2014-07-17Add option to pg_ctl to choose event source for loggingMagnus Hagander
pg_ctl will log to the Windows event log when it is running as a service, which is the primary way of running PostgreSQL on Windows. This option makes it possible to specify which event source to use for this, in order to separate different instances. The server logging itself is still controlled by the regular logging parameters, including a separate setting for the event source. The parameter to pg_ctl only controlls the logging from pg_ctl itself. MauMau, review in many iterations by Amit Kapila and me.
2014-06-29Add cluster_name GUC which is included in process titles if set.Andres Freund
When running several postgres clusters on one OS instance it's often inconveniently hard to identify which "postgres" process belongs to which postgres instance. Add the cluster_name GUC, whose value will be included as part of the process titles if set. With that processes can more easily identified using tools like 'ps'. To avoid problems with encoding mismatches between postgresql.conf, consoles, and individual databases replace non-ASCII chars in the name with question marks. The length is limited to NAMEDATALEN to make it less likely to truncate important information at the end of the status. Thomas Munro, with some adjustments by me and review by a host of people.
2014-06-28Remove Alpha and Tru64 support.Andres Freund
Support for running postgres on Alpha hasn't been tested for a long while. Due to Alpha's uniquely lax cache coherency model it's a hard to develop for platform (especially blindly!) and thought to be unlikely to currently work correctly. As Alpha is the only supported architecture for Tru64 drop support for it as well. Tru64's support has ended 2012 and it has been in maintenance-only mode for much longer. Also remove stray references to __ksr__ and ultrix defines.
2014-06-20Don't allow to disable backend assertions via the debug_assertions GUC.Andres Freund
The existance of the assert_enabled variable (backing the debug_assertions GUC) reduced the amount of knowledge some static code checkers (like coverity and various compilers) could infer from the existance of the assertion. That could have been solved by optionally removing the assertion_enabled variable from the Assert() et al macros at compile time when some special macro is defined, but the resulting complication doesn't seem to be worth the gain from having debug_assertions. Recompiling is fast enough. The debug_assertions GUC is still available, but readonly, as it's useful when diagnosing problems. The commandline/client startup option -A, which previously also allowed to enable/disable assertions, has been removed as it doesn't serve a purpose anymore. While at it, reduce code duplication in bufmgr.c and localbuf.c assertions checking for spurious buffer pins. That code had to be reindented anyway to cope with the assert_enabled removal.
2014-06-19Don't allow data_directory to be set in postgresql.auto.conf by ALTER SYSTEM.Fujii Masao
data_directory could be set both in postgresql.conf and postgresql.auto.conf so far. This could cause some problematic situations like circular definition. To avoid such situations, this commit forbids a user to set data_directory in postgresql.auto.conf. Backpatch this to 9.4 where ALTER SYSTEM command was introduced. Amit Kapila, reviewed by Abhijit Menon-Sen, with minor adjustments by me.
2014-05-25Small typo and formatting fixes in postgresql.conf.samplePeter Eisentraut
2014-05-17Fix a bunch of functions that were declared static then defined not-static.Tom Lane
Per testing with a compiler that whines about this.
2014-05-11Find postgresql.auto.conf in PGDATA even when postgresql.conf is elsewhere.Tom Lane
The original coding for ALTER SYSTEM made a fundamentally bogus assumption that postgresql.auto.conf could be sought relative to the main config file if we hadn't yet determined the value of data_directory. This fails for common arrangements with the config file elsewhere, as reported by Christoph Berg. The simplest fix is to not try to read postgresql.auto.conf until after SelectConfigFiles has chosen (and locked down) the data_directory setting. Because of the logic in ProcessConfigFile for handling resetting of GUCs that've been removed from the config file, we cannot easily read the main and auto config files separately; so this patch adopts a brute force approach of reading the main config file twice during postmaster startup. That's a tad ugly, but the actual time cost is likely to be negligible, and there's no time for a more invasive redesign before beta. With this patch, any attempt to set data_directory via ALTER SYSTEM will be silently ignored. It would probably be better to throw an error, but that can be dealt with later. This bug, however, would prevent any testing of ALTER SYSTEM by a significant fraction of the userbase, so it seems important to get it fixed before beta.
2014-05-08Increase the default value of effective_cache_size to 4GB.Tom Lane
Per discussion, the old value of 128MB is ridiculously small on modern machines; in fact, it's not even any larger than the default value of shared_buffers, which it certainly should be. Increase to 4GB, which is unlikely to be any worse than the old default for anyone, and should be noticeably better for most. Eventually we might have an autotuning scheme for this setting, but the recent attempt crashed and burned, so for now just do this.
2014-05-08Revert "Auto-tune effective_cache size to be 4x shared buffers"Tom Lane
This reverts commit ee1e5662d8d8330726eaef7d3110cb7add24d058, as well as a remarkably large number of followup commits, which were mostly concerned with the fact that the implementation didn't work terribly well. It still doesn't: we probably need some rather basic work in the GUC infrastructure if we want to fully support GUCs whose default varies depending on the value of another GUC. Meanwhile, it also emerged that there wasn't really consensus in favor of the definition the patch tried to implement (ie, effective_cache_size should default to 4 times shared_buffers). So whack it all back to where it was. In a followup commit, I'll do what was recently agreed to, which is to simply change the default to a higher value.
2014-05-06pgindent run for 9.4Bruce Momjian
This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
2014-04-10C comment: track_activity_query_size doesn't support memory unitsBruce Momjian
And explain why. Per report from Pavel Stehule
2014-04-05Fix processing of PGC_BACKEND GUC parameters on Windows.Tom Lane
EXEC_BACKEND builds (i.e., Windows) failed to absorb values of PGC_BACKEND parameters if they'd been changed post-startup via the config file. This for example prevented log_connections from working if it were turned on post-startup. The mechanism for handling this case has always been a bit of a kluge, and it wasn't revisited when we implemented EXEC_BACKEND. While in a normal forking environment new backends will inherit the postmaster's value of such settings, EXEC_BACKEND backends have to read the settings from the CONFIG_EXEC_PARAMS file, and they were mistakenly rejecting them. So this case has always been broken in the Windows port; so back-patch to all supported branches. Amit Kapila
2014-03-21Replace the XLogInsert slots with regular LWLocks.Heikki Linnakangas
The special feature the XLogInsert slots had over regular LWLocks is the insertingAt value that was updated atomically with releasing backends waiting on it. Add new functions to the LWLock API to do that, and replace the slots with LWLocks. This reduces the amount of duplicated code. (There's still some duplication, but at least it's all in lwlock.c now.) Reviewed by Andres Freund.
2014-03-20Again fix initialization of auto-tuned effective_cache_size.Tom Lane
The previous method was overly complex and underly correct; in particular, by assigning the default value with PGC_S_OVERRIDE, it prevented later attempts to change the setting in postgresql.conf, as noted by Jeff Janes. We should just assign the default value with source PGC_S_DYNAMIC_DEFAULT, which will have the desired priority relative to the boot_val as well as user-set values. There is still a gap in this method: if there's an explicit assignment of effective_cache_size = -1 in the postgresql.conf file, and that assignment appears before shared_buffers is assigned, the code will substitute 4 times the bootstrap default for shared_buffers, and that value will then persist (since it will have source PGC_S_FILE). I don't see any very nice way to avoid that though, and it's not a case to be expected in practice. The existing comments in guc-file.l look forward to a redesign of the DYNAMIC_DEFAULT mechanism; if that ever happens, we should consider this case as one of the things we'd like to improve.
2014-03-16Make punctuation consistentPeter Eisentraut
2014-03-16Cleanups from the remove-native-krb5 patchMagnus Hagander
krb_srvname is actually not available anymore as a parameter server-side, since with gssapi we accept all principals in our keytab. It's still used in libpq for client side specification. In passing remove declaration of krb_server_hostname, where all the functionality was already removed. Noted by Stephen Frost, though a different solution than his suggestion
2014-03-03Rename huge_tlb_pages to huge_pages, and improve docs.Heikki Linnakangas
Christian Kruse
2014-02-24Update and clarify ssl_ciphers defaultPeter Eisentraut
- Write HIGH:MEDIUM instead of DEFAULT:!LOW:!EXP for clarity. - Order 3DES last to work around inappropriate OpenSSL default. - Remove !MD5 and @STRENGTH, because they are irrelevant. - Add clarifying documentation. Effectively, the new default is almost the same as the old one, but it is arguably easier to understand and modify. Author: Marko Kreen <markokr@gmail.com>
2014-02-24Increase work_mem and maintenance_work_mem defaults by 4xBruce Momjian
New defaults are 4MB and 64MB.
2014-02-13Separate multixact freezing parameters from xid'sAlvaro Herrera
Previously we were piggybacking on transaction ID parameters to freeze multixacts; but since there isn't necessarily any relationship between rates of Xid and multixact consumption, this turns out not to be a good idea. Therefore, we now have multixact-specific freezing parameters: vacuum_multixact_freeze_min_age: when to remove multis as we come across them in vacuum (default to 5 million, i.e. early in comparison to Xid's default of 50 million) vacuum_multixact_freeze_table_age: when to force whole-table scans instead of scanning only the pages marked as not all visible in visibility map (default to 150 million, same as for Xids). Whichever of both which reaches the 150 million mark earlier will cause a whole-table scan. autovacuum_multixact_freeze_max_age: when for cause emergency, uninterruptible whole-table scans (default to 400 million, double as that for Xids). This means there shouldn't be more frequent emergency vacuuming than previously, unless multixacts are being used very rapidly. Backpatch to 9.3 where multixacts were made to persist enough to require freezing. To avoid an ABI break in 9.3, VacuumStmt has a couple of fields in an unnatural place, and StdRdOptions is split in two so that the newly added fields can go at the end. Patch by me, reviewed by Robert Haas, with additional input from Andres Freund and Tom Lane.
2014-02-03Make pg_basebackup skip temporary statistics files.Fujii Masao
The temporary statistics files don't need to be included in the backup because they are always reset at the beginning of the archive recovery. This patch changes pg_basebackup so that it skips all files located in $PGDATA/pg_stat_tmp or the directory specified by stats_temp_directory parameter.
2014-01-31Introduce replication slots.Robert Haas
Replication slots are a crash-safe data structure which can be created on either a master or a standby to prevent premature removal of write-ahead log segments needed by a standby, as well as (with hot_standby_feedback=on) pruning of tuples whose removal would cause replication conflicts. Slots have some advantages over existing techniques, as explained in the documentation. In a few places, we refer to the type of replication slots introduced by this patch as "physical" slots, because forthcoming patches for logical decoding will also have slots, but with somewhat different properties. Andres Freund and Robert Haas
2014-01-29Allow using huge TLB pages on Linux (MAP_HUGETLB)Heikki Linnakangas
This patch adds an option, huge_tlb_pages, which allows requesting the shared memory segment to be allocated using huge pages, by using the MAP_HUGETLB flag in mmap(). This can improve performance. The default is 'try', which means that we will attempt using huge pages, and fall back to non-huge pages if it doesn't work. Currently, only Linux has MAP_HUGETLB. On other platforms, the default 'try' behaves the same as 'off'. In the passing, don't try to round the mmap() size to a multiple of pagesize. mmap() doesn't require that, and there's no particular reason for PostgreSQL to do that either. When using MAP_HUGETLB, however, round the request size up to nearest 2MB boundary. This is to work around a bug in some Linux kernel versions, but also to avoid wasting memory, because the kernel will round the size up anyway. Many people were involved in writing this patch, including Christian Kruse, Richard Poole, Abhijit Menon-Sen, reviewed by Peter Geoghegan, Andres Freund and me.
2014-01-27Code review for auto-tuned effective_cache_size.Tom Lane
Fix integer overflow issue noted by Magnus Hagander, as well as a bunch of other infelicities in commit ee1e5662d8d8330726eaef7d3110cb7add24d058 and its unreasonably large number of followups.
2014-01-27Change the suffix of auto conf temporary file from "temp" to "tmp".Fujii Masao
Michael Paquier
2014-01-27Fix typos in comments for ALTER SYSTEM.Fujii Masao
Michael Paquier
2014-01-21Fix inadvertent semantics change in last patch to plug memory leaks.Robert Haas
Commit a5bca4ef034f71175d46462963af2329d22068c2 accidentally changed the semantics when the "skipping missing configuration file" is emitted, because it forced OK to true instead of leaving the value untouched. Spotted by Tom Lane.
2014-01-21Plug more memory leaks when reloading config file.Robert Haas
Commit 138184adc5f7c60c184972e4d23f8cdb32aed77d plugged some but not all of the leaks from commit 2a0c81a12c7e6c5ac1557b0f1f4a581f23fd4ca7. This tightens things up some more. Amit Kapila, per an observation by Tom Lane
2014-01-13Code improvements for ALTER SYSTEM .. SET.Robert Haas
Move FreeConfigVariables() later to make sure ErrorConfFile is valid when we use it, and get rid of an unnecessary string copy operation. Amit Kapila, kibitzed by me.
2014-01-07Update copyright for 2014Bruce Momjian
Update all files in head, and files COPYRIGHT and legal.sgml in all back branches.
2014-01-01Rename walLogHints to wal_log_hints for easier grepping.Robert Haas
Michael Paquier
2013-12-21Rename wal_log_hintbits to wal_log_hints, per discussion on pgsql-hackers.Fujii Masao
Sawada Masahiko
2013-12-18Add ALTER SYSTEM command to edit the server configuration file.Tatsuo Ishii
Patch contributed by Amit Kapila. Reviewed by Hari Babu, Masao Fujii, Boszormenyi Zoltan, Andres Freund, Greg Smith and others.
2013-12-13Don't let timeout interrupts happen unless ImmediateInterruptOK is set.Tom Lane
Serious oversight in commit 16e1b7a1b7f7ffd8a18713e83c8cd72c9ce48e07: we should not allow an interrupt to take control away from mainline code except when ImmediateInterruptOK is set. Just to be safe, let's adopt the same save-clear-restore dance that's been used for many years in HandleCatchupInterrupt and HandleNotifyInterrupt, so that nothing bad happens if a timeout handler invokes code that tests or even manipulates ImmediateInterruptOK. Per report of "stuck spinlock" failures from Christophe Pettus, though many other symptoms are possible. Diagnosis by Andres Freund.
2013-12-13Add GUC to enable WAL-logging of hint bits, even with checksums disabled.Heikki Linnakangas
WAL records of hint bit updates is useful to tools that want to examine which pages have been modified. In particular, this is required to make the pg_rewind tool safe (without checksums). This can also be used to test how much extra WAL-logging would occur if you enabled checksums, without actually enabling them (which you can't currently do without re-initdb'ing). Sawada Masahiko, docs by Samrat Revagade. Reviewed by Dilip Kumar, with further changes by me.