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2015-01-15Fix thinko in re-setting wal_log_hints flag from a parameter-change record.Heikki Linnakangas
The flag is supposed to be copied from the record. Same issue with track_commit_timestamps, but that's master-only. Report and fix by Petr Jalinek. Backpatch to 9.4, where wal_log_hints was added.
2015-01-07Don't open a WAL segment for writing at end of recovery.Heikki Linnakangas
Since commit ba94518a, we used XLogFileOpen to open the next segment for writing, but if the end-of-recovery happens exactly at a segment boundary, the new segment might not exist yet. (Before ba94518a, XLogFileOpen was correct, because we would open the previous segment if the switch happened at the boundary.) Instead of trying to create it if necessary, it's simpler to not bother opening the segment at all. XLogWrite() will open or create it soon anyway, after writing the checkpoint or end-of-recovery record. Reported by Andres Freund.
2015-01-06Update copyright for 2015Bruce Momjian
Backpatch certain files through 9.0
2015-01-04Remove superflous variable from xlogreader's XLogFindNextRecord().Andres Freund
Pointed out by Coverity. Since this is mere, and debatable, cosmetics I'm not backpatching this.
2015-01-03Treat negative values of recovery_min_apply_delay as having no effect.Tom Lane
At one point in the development of this feature, it was claimed that allowing negative values would be useful to compensate for timezone differences between master and slave servers. That was based on a mistaken assumption that commit timestamps are recorded in local time; but of course they're in UTC. Nor is a negative apply delay likely to be a sane way of coping with server clock skew. However, the committed patch still treated negative delays as doing something, and the timezone misapprehension survived in the user documentation as well. If recovery_min_apply_delay were a proper GUC we'd just set the minimum allowed value to be zero; but for the moment it seems better to treat negative settings as if they were zero. In passing do some extra wordsmithing on the parameter's documentation, including correcting a second misstatement that the parameter affects processing of Restore Point records. Issue noted by Michael Paquier, who also provided the code patch; doc changes by me. Back-patch to 9.4 where the feature was introduced.
2014-12-25Convert the PGPROC->lwWaitLink list into a dlist instead of open coding it.Andres Freund
Besides being shorter and much easier to read it changes the logic in LWLockRelease() to release all shared lockers when waking up any. This can yield some significant performance improvements - and the fairness isn't really much worse than before, as we always allowed new shared lockers to jump the queue.
2014-12-23Revert "Use a bitmask to represent role attributes"Alvaro Herrera
This reverts commit 1826987a46d079458007b7b6bbcbbd852353adbb. The overall design was deemed unacceptable, in discussion following the previous commit message; we might find some parts of it still salvageable, but I don't want to be on the hook for fixing it, so let's wait until we have a new patch.
2014-12-23Use a bitmask to represent role attributesAlvaro Herrera
The previous representation using a boolean column for each attribute would not scale as well as we want to add further attributes. Extra auxilliary functions are added to go along with this change, to make up for the lost convenience of access of the old representation. Catalog version bumped due to change in catalogs and the new functions. Author: Adam Brightwell, minor tweaks by Álvaro Reviewed by: Stephen Frost, Andres Freund, Álvaro Herrera
2014-12-21Fix file descriptor leak at end of recovery.Heikki Linnakangas
XLogFileInit() returns a file descriptor, which needs to be closed. The leak was short-lived, since the startup process exits shortly afterwards, but it was clearly a bug, nevertheless. Per Coverity report.
2014-12-19Fix timestamp in end-of-recovery WAL records.Heikki Linnakangas
We used time(null) to set a TimestampTz field, which gave bogus results. Noticed while looking at pg_xlogdump output. Backpatch to 9.3 and above, where the fast promotion was introduced.
2014-12-18Improve hash_create's API for selecting simple-binary-key hash functions.Tom Lane
Previously, if you wanted anything besides C-string hash keys, you had to specify a custom hashing function to hash_create(). Nearly all such callers were specifying tag_hash or oid_hash; which is tedious, and rather error-prone, since a caller could easily miss the opportunity to optimize by using hash_uint32 when appropriate. Replace this with a design whereby callers using simple binary-data keys just specify HASH_BLOBS and don't need to mess with specific support functions. hash_create() itself will take care of optimizing when the key size is four bytes. This nets out saving a few hundred bytes of code space, and offers a measurable performance improvement in tidbitmap.c (which was not exploiting the opportunity to use hash_uint32 for its 4-byte keys). There might be some wins elsewhere too, I didn't analyze closely. In future we could look into offering a similar optimized hashing function for 8-byte keys. Under this design that could be done in a centralized and machine-independent fashion, whereas getting it right for keys of platform-dependent sizes would've been notationally painful before. For the moment, the old way still works fine, so as not to break source code compatibility for loadable modules. Eventually we might want to remove tag_hash and friends from the exported API altogether, since there's no real need for them to be explicitly referenced from outside dynahash.c. Teodor Sigaev and Tom Lane
2014-12-18Change how first WAL segment on new timeline after promotion is created.Heikki Linnakangas
Two changes: 1. When copying a WAL segment from old timeline to create the first segment on the new timeline, only copy up to the point where the timeline switch happens, and zero-fill the rest. This avoids corner cases where we might think that the copied WAL from the previous timeline belong to the new timeline. 2. If the timeline switch happens at a segment boundary, don't copy the whole old segment to the new timeline. It's pointless, because it's 100% identical to the old segment.
2014-12-18Fix (re-)starting from a basebackup taken off a standby after a failure.Andres Freund
When starting up from a basebackup taken off a standby extra logic has to be applied to compute the point where the data directory is consistent. Normal base backups use a WAL record for that purpose, but that isn't possible on a standby. That logic had a error check ensuring that the cluster's control file indicates being in recovery. Unfortunately that check was too strict, disregarding the fact that the control file could also indicate that the cluster was shut down while in recovery. That's possible when the a cluster starting from a basebackup is shut down before the backup label has been removed. When everything goes well that's a short window, but when either restore_command or primary_conninfo isn't configured correctly the window can get much wider. That's because inbetween reading and unlinking the label we restore the last checkpoint from WAL which can need additional WAL. To fix simply also allow starting when the control file indicates "shutdown in recovery". There's nicer fixes imaginable, but they'd be more invasive. Backpatch to 9.2 where support for taking basebackups from standbys was added.
2014-12-07Tweaks for recovery_target_actionSimon Riggs
Rename parameter action_at_recovery_target to recovery_target_action suggested by Christoph Berg. Place into recovery.conf suggested by Fujii Masao, replacing (deprecating) earlier parameters, per Michael Paquier.
2014-12-03Keep track of transaction commit timestampsAlvaro Herrera
Transactions can now set their commit timestamp directly as they commit, or an external transaction commit timestamp can be fed from an outside system using the new function TransactionTreeSetCommitTsData(). This data is crash-safe, and truncated at Xid freeze point, same as pg_clog. This module is disabled by default because it causes a performance hit, but can be enabled in postgresql.conf requiring only a server restart. A new test in src/test/modules is included. Catalog version bumped due to the new subdirectory within PGDATA and a couple of new SQL functions. Authors: Álvaro Herrera and Petr Jelínek Reviewed to varying degrees by Michael Paquier, Andres Freund, Robert Haas, Amit Kapila, Fujii Masao, Jaime Casanova, Simon Riggs, Steven Singer, Peter Eisentraut
2014-12-03Fix typosAlvaro Herrera
2014-11-28Update transaction README for persistent multixactsAlvaro Herrera
Multixacts are now maintained during recovery, but the README didn't get the memo. Backpatch to 9.3, where the divergence was introduced.
2014-11-28Fix assertion failure at end of PITR.Heikki Linnakangas
InitXLogInsert() cannot be called in a critical section, because it allocates memory. But CreateCheckPoint() did that, when called for the end-of-recovery checkpoint by the startup process. In the passing, fix the scratch space allocation in InitXLogInsert to go to the right memory context. Also update the comment at InitXLOGAccess, which hasn't been totally accurate since hot standby was introduced (in a hot standby backend, InitXLOGAccess isn't called at backend startup). Reported by Michael Paquier
2014-11-25action_at_recovery_target recovery config optionSimon Riggs
action_at_recovery_target = pause | promote | shutdown Petr Jelinek Reviewed by Muhammad Asif Naeem, Fujji Masao and Simon Riggs
2014-11-24Distinguish XLOG_FPI records generated for hint-bit updates.Heikki Linnakangas
Add a new XLOG_FPI_FOR_HINT record type, and use that for full-page images generated for hint bit updates, when checksums are enabled. The new record type is replayed exactly the same as XLOG_FPI, but allows them to be tallied separately e.g. in pg_xlogdump.
2014-11-21Fix bogus comments in XLogRecordAssembleHeikki Linnakangas
Pointed out by Michael Paquier
2014-11-20Revamp the WAL record format.Heikki Linnakangas
Each WAL record now carries information about the modified relation and block(s) in a standardized format. That makes it easier to write tools that need that information, like pg_rewind, prefetching the blocks to speed up recovery, etc. There's a whole new API for building WAL records, replacing the XLogRecData chains used previously. The new API consists of XLogRegister* functions, which are called for each buffer and chunk of data that is added to the record. The new API also gives more control over when a full-page image is written, by passing flags to the XLogRegisterBuffer function. This also simplifies the XLogReadBufferForRedo() calls. The function can dig the relation and block number from the WAL record, so they no longer need to be passed as arguments. For the convenience of redo routines, XLogReader now disects each WAL record after reading it, copying the main data part and the per-block data into MAXALIGNed buffers. The data chunks are not aligned within the WAL record, but the redo routines can assume that the pointers returned by XLogRecGet* functions are. Redo routines are now passed the XLogReaderState, which contains the record in the already-disected format, instead of the plain XLogRecord. The new record format also makes the fixed size XLogRecord header smaller, by removing the xl_len field. The length of the "main data" portion is now stored at the end of the WAL record, and there's a separate header after XLogRecord for it. The alignment padding at the end of XLogRecord is also removed. This compansates for the fact that the new format would otherwise be more bulky than the old format. Reviewed by Andres Freund, Amit Kapila, Michael Paquier, Alvaro Herrera, Fujii Masao.
2014-11-15Ensure unlogged tables are reset even if crash recovery errors out.Andres Freund
Unlogged relations are reset at the end of crash recovery as they're only synced to disk during a proper shutdown. Unfortunately that and later steps can fail, e.g. due to running out of space. This reset was, up to now performed after marking the database as having finished crash recovery successfully. As out of space errors trigger a crash restart that could lead to the situation that not all unlogged relations are reset. Once that happend usage of unlogged relations could yield errors like "could not open file "...": No such file or directory". Luckily clusters that show the problem can be fixed by performing a immediate shutdown, and starting the database again. To fix, just call ResetUnloggedRelations(UNLOGGED_RELATION_INIT) earlier, before marking the database as having successfully recovered. Discussion: 20140912112246.GA4984@alap3.anarazel.de Backpatch to 9.1 where unlogged tables were introduced. Abhijit Menon-Sen and Andres Freund
2014-11-14Allow interrupting GetMultiXactIdMembersAlvaro Herrera
This function has a loop which can lead to uninterruptible process "stalls" (actually infinite loops) when some bugs are triggered. Avoid that unpleasant situation by adding a check for interrupts in a place that shouldn't degrade performance in the normal case. Backpatch to 9.3. Older branches have an identical loop here, but the aforementioned bugs are only a problem starting in 9.3 so there doesn't seem to be any point in backpatching any further.
2014-11-13Fix race condition between hot standby and restoring a full-page image.Heikki Linnakangas
There was a window in RestoreBackupBlock where a page would be zeroed out, but not yet locked. If a backend pinned and locked the page in that window, it saw the zeroed page instead of the old page or new page contents, which could lead to missing rows in a result set, or errors. To fix, replace RBM_ZERO with RBM_ZERO_AND_LOCK, which atomically pins, zeroes, and locks the page, if it's not in the buffer cache already. In stable branches, the old RBM_ZERO constant is renamed to RBM_DO_NOT_USE, to avoid breaking any 3rd party extensions that might use RBM_ZERO. More importantly, this avoids renumbering the other enum values, which would cause even bigger confusion in extensions that use ReadBufferExtended, but haven't been recompiled. Backpatch to all supported versions; this has been racy since hot standby was introduced.
2014-11-13Fix XLogReadBufferForRedoExtended to get cleanup lock when asked to do so.Heikki Linnakangas
2014-11-07Fix building with WAL_DEBUG.Heikki Linnakangas
Now that the backup blocks are appended to the WAL record in xloginsert.c, XLogInsert doesn't see them anymore and cannot remove them from the version reconstructed for xlog_outdesc. This makes running with wal_debug=on more expensive, as we now make (unnecessary) temporary copies of the backup blocks, but it doesn't seem worth convoluting the code to keep that optimization. Reported by Alvaro Herrera.
2014-11-07BRIN: Block Range IndexesAlvaro Herrera
BRIN is a new index access method intended to accelerate scans of very large tables, without the maintenance overhead of btrees or other traditional indexes. They work by maintaining "summary" data about block ranges. Bitmap index scans work by reading each summary tuple and comparing them with the query quals; all pages in the range are returned in a lossy TID bitmap if the quals are consistent with the values in the summary tuple, otherwise not. Normal index scans are not supported because these indexes do not store TIDs. As new tuples are added into the index, the summary information is updated (if the block range in which the tuple is added is already summarized) or not; in the latter case, a subsequent pass of VACUUM or the brin_summarize_new_values() function will create the summary information. For data types with natural 1-D sort orders, the summary info consists of the maximum and the minimum values of each indexed column within each page range. This type of operator class we call "Minmax", and we supply a bunch of them for most data types with B-tree opclasses. Since the BRIN code is generalized, other approaches are possible for things such as arrays, geometric types, ranges, etc; even for things such as enum types we could do something different than minmax with better results. In this commit I only include minmax. Catalog version bumped due to new builtin catalog entries. There's more that could be done here, but this is a good step forwards. Loosely based on ideas from Simon Riggs; code mostly by Álvaro Herrera, with contribution by Heikki Linnakangas. Patch reviewed by: Amit Kapila, Heikki Linnakangas, Robert Haas. Testing help from Jeff Janes, Erik Rijkers, Emanuel Calvo. PS: The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 318633.
2014-11-06Prevent the unnecessary creation of .ready file for the timeline history file.Fujii Masao
Previously .ready file was created for the timeline history file at the end of an archive recovery even when WAL archiving was not enabled. This creation is unnecessary and causes .ready file to remain infinitely. This commit changes an archive recovery so that it creates .ready file for the timeline history file only when WAL archiving is enabled. Backpatch to all supported versions.
2014-11-06Move the backup-block logic from XLogInsert to a new file, xloginsert.c.Heikki Linnakangas
xlog.c is huge, this makes it a little bit smaller, which is nice. Functions related to putting together the WAL record are in xloginsert.c, and the lower level stuff for managing WAL buffers and such are in xlog.c. Also move the definition of XLogRecord to a separate header file. This causes churn in the #includes of all the files that write WAL records, and redo routines, but it avoids pulling in xlog.h into most places. Reviewed by Michael Paquier, Alvaro Herrera, Andres Freund and Amit Kapila.
2014-11-04Switch to CRC-32C in WAL and other places.Heikki Linnakangas
The old algorithm was found to not be the usual CRC-32 algorithm, used by Ethernet et al. We were using a non-reflected lookup table with code meant for a reflected lookup table. That's a strange combination that AFAICS does not correspond to any bit-wise CRC calculation, which makes it difficult to reason about its properties. Although it has worked well in practice, seems safer to use a well-known algorithm. Since we're changing the algorithm anyway, we might as well choose a different polynomial. The Castagnoli polynomial has better error-correcting properties than the traditional CRC-32 polynomial, even if we had implemented it correctly. Another reason for picking that is that some new CPUs have hardware support for calculating CRC-32C, but not CRC-32, let alone our strange variant of it. This patch doesn't add any support for such hardware, but a future patch could now do that. The old algorithm is kept around for tsquery and pg_trgm, which use the values in indexes that need to remain compatible so that pg_upgrade works. While we're at it, share the old lookup table for CRC-32 calculation between hstore, ltree and core. They all use the same table, so might as well.
2014-10-29Avoid setup work for invalidation messages at start-of-(sub)xact.Robert Haas
Instead of initializing a new TransInvalidationInfo for every transaction or subtransaction, we can just do it for those transactions or subtransactions that actually need to queue invalidation messages. That also avoids needing to free those entries at the end of a transaction or subtransaction that does not generate any invalidation messages, which is by far the common case. Patch by me. Review by Simon Riggs and Andres Freund.
2014-10-23Prevent the already-archived WAL file from being archived again.Fujii Masao
Previously the archive recovery always created .ready file for the last WAL file of the old timeline at the end of recovery even when it's restored from the archive and has .done file. That is, there was the case where the WAL file had both .ready and .done files. This caused the already-archived WAL file to be archived again. This commit prevents the archive recovery from creating .ready file for the last WAL file if it has .done file, in order to prevent it from being archived again. This bug was added when cascading replication feature was introduced, i.e., the commit 5286105800c7d5902f98f32e11b209c471c0c69c. So, back-patch to 9.2, where cascading replication was added. Reviewed by Michael Paquier
2014-10-21Don't duplicate log_checkpoint messages for both of restart and checkpoints.Andres Freund
The duplication originated in cdd46c765, where restartpoints were introduced. In LogCheckpointStart's case the duplication actually lead to the compiler's format string checking not to be effective because the format string wasn't constant. Arguably these messages shouldn't be elog(), but ereport() style messages. That'd even allow to translate the messages... But as there's more mistakes of that kind in surrounding code, it seems better to change that separately.
2014-10-21Renumber CHECKPOINT_* flags.Andres Freund
Commit 7dbb6069382 added a new CHECKPOINT_FLUSH_ALL flag. As that commit needed to be backpatched I didn't change the numeric values of the existing flags as that could lead to nastly problems if any external code issued checkpoints. That's not a concern on master, so renumber them there. Also add a comment about CHECKPOINT_FLUSH_ALL above CreateCheckPoint().
2014-10-20Flush unlogged table's buffers when copying or moving databases.Andres Freund
CREATE DATABASE and ALTER DATABASE .. SET TABLESPACE copy the source database directory on the filesystem level. To ensure the on disk state is consistent they block out users of the affected database and force a checkpoint to flush out all data to disk. Unfortunately, up to now, that checkpoint didn't flush out dirty buffers from unlogged relations. That bug means there could be leftover dirty buffers in either the template database, or the database in its old location. Leading to problems when accessing relations in an inconsistent state; and to possible problems during shutdown in the SET TABLESPACE case because buffers belonging files that don't exist anymore are flushed. This was reported in bug #10675 by Maxim Boguk. Fix by Pavan Deolasee, modified somewhat by me. Reviewed by MauMau and Fujii Masao. Backpatch to 9.1 where unlogged tables were introduced.
2014-10-12Message improvementsPeter Eisentraut
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.
2014-10-01Rename CACHE_LINE_SIZE to PG_CACHE_LINE_SIZE.Andres Freund
As noted in http://bugs.debian.org/763098 there is a conflict between postgres' definition of CACHE_LINE_SIZE and the definition by various *bsd platforms. It's debatable who has the right to define such a name, but postgres' use was only introduced in 375d8526f290 (9.4), so it seems like a good idea to rename it. Discussion: 20140930195756.GC27407@msg.df7cb.de Per complaint of Christoph Berg in the above email, although he's not the original bug reporter. Backpatch to 9.4 where the define was introduced.
2014-09-22Remove most volatile qualifiers from xlog.cAndres Freund
For the reason outlined in df4077cda2e also remove volatile qualifiers from xlog.c. Some of these uses of volatile have been added after noticing problems back when spinlocks didn't imply compiler barriers. So they are a good test - in fact removing the volatiles breaks when done without the barriers in spinlocks present. Several uses of volatile remain where they are explicitly used to access shared memory without locks. These locations are ok with slightly out of date data, but removing the volatile might lead to the variables never being reread from memory. These uses could also be replaced by barriers, but that's a separate change of doubtful value.
2014-09-22Improve code around the recently added rm_identify rmgr callback.Andres Freund
There are four weaknesses in728f152e07f998d2cb4fe5f24ec8da2c3bda98f2: * append_init() in heapdesc.c was ugly and required that rm_identify return values are only valid till the next call. Instead just add a couple more switch() cases for the INIT_PAGE cases. Now the returned value will always be valid. * a couple rm_identify() callbacks missed masking xl_info with ~XLR_INFO_MASK. * pg_xlogdump didn't map a NULL rm_identify to UNKNOWN or a similar string. * append_init() was called when id=NULL - which should never actually happen. But it's better to be careful.
2014-09-19Add rmgr callback to name xlog record types for display purposes.Andres Freund
This is primarily useful for the upcoming pg_xlogdump --stats feature, but also allows to remove some duplicated code in the rmgr_desc routines. Due to the separation and harmonization, the output of dipsplayed records changes somewhat. But since this isn't enduser oriented content that's ok. It's potentially desirable to further change pg_xlogdump's display of records. It previously wasn't possible to show the record type separately from the description forcing it to be in the last column. But that's better done in a separate commit. Author: Abhijit Menon-Sen, slightly editorialized by me Reviewed-By: Álvaro Herrera, Andres Freund, and Heikki Linnakangas Discussion: 20140604104716.GA3989@toroid.org
2014-09-02Refactor per-page logic common to all redo routines to a new function.Heikki Linnakangas
Every redo routine uses the same idiom to determine what to do to a page: check if there's a backup block for it, and if not read, the buffer if the block exists, and check its LSN. Refactor that into a common function, XLogReadBufferForRedo, making all the redo routines shorter and more readable. This has no user-visible effect, and makes no changes to the WAL format. Reviewed by Andres Freund, Alvaro Herrera, Michael Paquier.
2014-08-29pg_is_xlog_replay_paused(): remove super-user-only restrictionBruce Momjian
Also update docs to mention which function are super-user-only. Report by sys-milan@statpro.com Backpatch through 9.4
2014-08-18Replace a few strncmp() calls with strlcpy().Noah Misch
strncmp() is a specialized API unsuited for routine copying into fixed-size buffers. On a system where the length of a single filename can exceed MAXPGPATH, the pg_archivecleanup change prevents a simple crash in the subsequent strlen(). Few filesystems support names that long, and calling pg_archivecleanup with untrusted input is still not a credible use case. Therefore, no back-patch. David Rowley
2014-07-31Move log_newpage and log_newpage_buffer to xlog.c.Heikki Linnakangas
log_newpage is used by many indexams, in addition to heap, but for historical reasons it's always been part of the heapam rmgr. Starting with 9.3, we have another WAL record type for logging an image of a page, XLOG_FPI. Simplify things by moving log_newpage and log_newpage_buffer to xlog.c, and switch to using the XLOG_FPI record type. Bump the WAL version number because the code to replay the old HEAP_NEWPAGE records is removed.
2014-07-29Avoid uselessly looking up old LOCK_ONLY multixactsAlvaro Herrera
Commit 0ac5ad5134f2 removed an optimization in multixact.c that skipped fetching members of MultiXactId that were older than our OldestVisibleMXactId value. The reason this was removed is that it is possible for multixacts that contain updates to be older than that value. However, if the caller is certain that the multi does not contain an update (because the infomask bits say so), it can pass this info down to GetMultiXactIdMembers, enabling it to use the old optimization. Pointed out by Andres Freund in 20131121200517.GM7240@alap2.anarazel.de
2014-07-29Oops, fix recoveryStopsBefore functions for regular commits.Heikki Linnakangas
Pointed out by Tom Lane. Backpatch to 9.4, the code was structured differently in earlier branches and didn't have this mistake.
2014-07-29Treat 2PC commit/abort the same as regular xacts in recovery.Heikki Linnakangas
There were several oversights in recovery code where COMMIT/ABORT PREPARED records were ignored: * pg_last_xact_replay_timestamp() (wasn't updated for 2PC commits) * recovery_min_apply_delay (2PC commits were applied immediately) * recovery_target_xid (recovery would not stop if the XID used 2PC) The first of those was reported by Sergiy Zuban in bug #11032, analyzed by Tom Lane and Andres Freund. The bug was always there, but was masked before commit d19bd29f07aef9e508ff047d128a4046cc8bc1e2, because COMMIT PREPARED always created an extra regular transaction that was WAL-logged. Backpatch to all supported versions (older versions didn't have all the features and therefore didn't have all of the above bugs).
2014-07-24Fix checkpointer crash in EXEC_BACKEND builds.Robert Haas
Nothing in the checkpointer calls InitXLOGAccess(), so WALInsertLocks never got initialized there. Without EXEC_BACKEND, it works anyway because the correct value is inherited from the postmaster, but with EXEC_BACKEND we've got a problem. The problem appears to have been introduced by commit 68a2e52bbaf98f136a96b3a0d734ca52ca440a95. To fix, move the relevant initialization steps from InitXLOGAccess() to XLOGShmemInit(), making this more parallel to what we do elsewhere. Amit Kapila