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* Modify BufferGetPage() to prepare for "snapshot too old" featureKevin Grittner2016-04-08
| | | | | | | | | | | This patch is a no-op patch which is intended to reduce the chances of failures of omission once the functional part of the "snapshot too old" patch goes in. It adds parameters for snapshot, relation, and an enum to specify whether the snapshot age check needs to be done for the page at this point. This initial patch passes NULL for the first two new parameters and BGP_NO_SNAPSHOT_TEST for the third. The follow-on patch will change the places where the test needs to be made.
* Revert CREATE INDEX ... INCLUDING ...Teodor Sigaev2016-04-08
| | | | | | It's not ready yet, revert two commits 690c543550b0d2852060c18d270cdb534d339d9a - unstable test output 386e3d7609c49505e079c40c65919d99feb82505 - patch itself
* CREATE INDEX ... INCLUDING (column[, ...])Teodor Sigaev2016-04-08
| | | | | | | | | | Now indexes (but only B-tree for now) can contain "extra" column(s) which doesn't participate in index structure, they are just stored in leaf tuples. It allows to use index only scan by using single index instead of two or more indexes. Author: Anastasia Lubennikova with minor editorializing by me Reviewers: David Rowley, Peter Geoghegan, Jeff Janes
* Introduce traversalValue for SP-GiST scanTeodor Sigaev2016-03-30
| | | | | | | | | | | | | During scan sometimes it would be very helpful to know some information about parent node or all ancestor nodes. Right now reconstructedValue could be used but it's not a right usage of it (range opclass uses that). traversalValue is arbitrary piece of memory in separate MemoryContext while reconstructedVale should have the same type as indexed column. Subsequent patches for range opclass and quad4d tree will use it. Author: Alexander Lebedev, Teodor Sigaev
* Suppress compiler warning.Tom Lane2016-01-21
| | | | | | | | Given the limited range of i, these shifts should not cause any problem, but that apparently doesn't stop some compilers from whining about them. David Rowley
* Improve index AMs' opclass validation procedures.Tom Lane2016-01-21
| | | | | | | | | | | | | | | | | | | | The amvalidate functions added in commit 65c5fcd353a859da were on the crude side. Improve them in a few ways: * Perform signature checking for operators and support functions. * Apply more thorough checks for missing operators and functions, where possible. * Instead of reporting problems as ERRORs, report most problems as INFO messages and make the amvalidate function return FALSE. This allows more than one problem to be discovered per run. * Report object names rather than OIDs, and work a bit harder on making the messages understandable. Also, remove a few more opr_sanity regression test queries that are now superseded by the amvalidate checks.
* Restructure index access method API to hide most of it at the C level.Tom Lane2016-01-17
| | | | | | | | | | | | | | | | | | | | | | | | This patch reduces pg_am to just two columns, a name and a handler function. All the data formerly obtained from pg_am is now provided in a C struct returned by the handler function. This is similar to the designs we've adopted for FDWs and tablesample methods. There are multiple advantages. For one, the index AM's support functions are now simple C functions, making them faster to call and much less error-prone, since the C compiler can now check function signatures. For another, this will make it far more practical to define index access methods in installable extensions. A disadvantage is that SQL-level code can no longer see attributes of index AMs; in particular, some of the crosschecks in the opr_sanity regression test are no longer possible from SQL. We've addressed that by adding a facility for the index AM to perform such checks instead. (Much more could be done in that line, but for now we're content if the amvalidate functions more or less replace what opr_sanity used to do.) We might also want to expose some sort of reporting functionality, but this patch doesn't do that. Alexander Korotkov, reviewed by Petr Jelínek, and rather heavily editorialized on by me.
* Fix overly-strict assertions in spgtextproc.c.Tom Lane2016-01-02
| | | | | | | | | | | | | | | | | spg_text_inner_consistent is capable of reconstructing an empty string to pass down to the next index level; this happens if we have an empty string coming in, no prefix, and a dummy node label. (In practice, what is needed to trigger that is insertion of a whole bunch of empty-string values.) Then, we will arrive at the next level with in->level == 0 and a non-NULL (but zero length) in->reconstructedValue, which is valid but the Assert tests weren't expecting it. Per report from Andreas Seltenreich. This has no impact in non-Assert builds, so should not be a problem in production, but back-patch to all affected branches anyway. In passing, remove a couple of useless variable initializations and shorten the code by not duplicating DatumGetPointer() calls.
* Update copyright for 2016Bruce Momjian2016-01-02
| | | | Backpatch certain files through 9.1
* Don't assume that PageIsEmpty() returns true on an all-zeros page.Heikki Linnakangas2015-07-27
| | | | | | | | It does currently, and I don't see us changing that any time soon, but we don't make that assumption anywhere else. Per Tom Lane's suggestion. Backpatch to 9.2, like the previous patch that added this assumption.
* Fix handling of all-zero pages in SP-GiST vacuum.Heikki Linnakangas2015-07-27
| | | | | | | | | | | | SP-GiST initialized an all-zeros page at vacuum, but that was not WAL-logged, which is not safe. You might get a torn page write, when it gets flushed to disk, and end-up with a half-initialized index page. To fix, leave it in the all-zeros state, and add it to the FSM. It will be initialized when reused. Also don't set the page-deleted flag when recycling an empty page. That was also not WAL-logged, and a torn write of that would cause the page to have an invalid checksum. Backpatch to 9.2, where SP-GiST indexes were added.
* Sanity-check that a page zeroed by redo routine is marked with WILL_INIT.Heikki Linnakangas2015-07-20
| | | | | | | | | | | | | | | There was already a sanity-check in the other direction: if a page was marked with WILL_INIT, it had to be initialized by the redo routine. It's not strictly necessary for correctness that a page is marked with WILL_INIT if it's going to be initialized at redo, but it's a missed optimization if nothing else. Fix a few instances of this issue in SP-GiST, where a block in WAL record was not marked with WILL_INIT, but was in fact always initialized at redo. We were creating a full-page image of the page unnecessarily in those cases. Backpatch to 9.5, where the new WILL_INIT flag was added.
* pgindent run for 9.5Bruce Momjian2015-05-23
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* Move strategy numbers to include/access/stratnum.hAlvaro Herrera2015-05-15
| | | | | | | | | | | | | | | | | | | | For upcoming BRIN opclasses, it's convenient to have strategy numbers defined in a single place. Since there's nothing appropriate, create it. The StrategyNumber typedef now lives there, as well as existing strategy numbers for B-trees (from skey.h) and R-tree-and-friends (from gist.h). skey.h is forced to include stratnum.h because of the StrategyNumber typedef, but gist.h is not; extensions that currently rely on gist.h for rtree strategy numbers might need to add a new A few .c files can stop including skey.h and/or gist.h, which is a nice side benefit. Per discussion: https://www.postgresql.org/message-id/20150514232132.GZ2523@alvh.no-ip.org Authored by Emre Hasegeli and Álvaro. (It's not clear to me why bootscanner.l has any #include lines at all.)
* Add support for index-only scans in GiST.Heikki Linnakangas2015-03-26
| | | | | | | | | | | | | | This adds a new GiST opclass method, 'fetch', which is used to reconstruct the original Datum from the value stored in the index. Also, the 'canreturn' index AM interface function gains a new 'attno' argument. That makes it possible to use index-only scans on a multi-column index where some of the opclasses support index-only scans but some do not. This patch adds support in the box and point opclasses. Other opclasses can added later as follow-on patches (btree_gist would be particularly interesting). Anastasia Lubennikova, with additional fixes and modifications by me.
* Update copyright for 2015Bruce Momjian2015-01-06
| | | | Backpatch certain files through 9.0
* Revamp the WAL record format.Heikki Linnakangas2014-11-20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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.
* Fix generation of SP-GiST vacuum WAL records.Heikki Linnakangas2014-11-07
| | | | | I broke these in 8776faa81cb651322b8993422bdd4633f1f6a487. Backpatch to 9.4, where that was done.
* Move the backup-block logic from XLogInsert to a new file, xloginsert.c.Heikki Linnakangas2014-11-06
| | | | | | | | | | | | 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.
* Refactor per-page logic common to all redo routines to a new function.Heikki Linnakangas2014-09-02
| | | | | | | | | | | | 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.
* Move log_newpage and log_newpage_buffer to xlog.c.Heikki Linnakangas2014-07-31
| | | | | | | | | | | 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.
* Fix infinite loop when splitting inner tuples in SPGiST text indexes.Tom Lane2014-06-09
| | | | | | | | | | | | | | | | | | | | | | | Previously, the code used a node label of zero both for strings that contain no bytes beyond the inner tuple's prefix, and for cases where an "allTheSame" inner tuple has to be split to allow a string with a different next byte to be inserted into it. Failing to distinguish these cases meant that if a string ending with the current prefix needed to be inserted into an allTheSame tuple, we got into an infinite loop, because after splitting the tuple we'd descend into the child allTheSame tuple and then find we need to split again. To fix, instead use -1 and -2 as the node labels for these two cases. This requires widening the node label type from "char" to int2, but fortunately SPGiST stores all pass-by-value node label types in their Datum representation, which means that this change is transparently upward compatible so far as the on-disk representation goes. We continue to recognize zero as a dummy node label for reading purposes, but will not attempt to push new index entries down into such a label, so that the loop won't occur even when dealing with an existing index. Per report from Teodor Sigaev. Back-patch to 9.2 where the faulty code was introduced.
* Adjust SP-GiST WAL record formats to reduce alignment padding.Heikki Linnakangas2014-06-05
| | | | | | | | | | | | | | | | | | The way the code was written, the padding was copied from uninitialized memory areas.. Because the structs are local variables in the code where the WAL records are constructed, making them larger and zeroing the padding bytes would not make the code very pretty, so rather than fixing this directly by zeroing out the padding bytes, it seems more clear to not try to align the tuples in the WAL records. The redo functions are taught to copy the tuple header to a local variable to avoid unaligned access. Stable-branches have the same problem, but we can't change the WAL format there, so fix in master only. Reading a few random extra bytes at the stack is harmless in practice, so it's not worth crafting a different back-patchable fix. Per reports from Kevin Grittner and Andres Freund, using clang static analyzer and Valgrind, respectively.
* pgindent run for 9.4Bruce Momjian2014-05-06
| | | | | This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
* Avoid allocations in critical sections.Heikki Linnakangas2014-04-04
| | | | If a palloc in a critical section fails, it becomes a PANIC.
* Allow use of "z" flag in our printf calls, and use it where appropriate.Tom Lane2014-01-23
| | | | | | | | | | | | | | | | | | | | | | | | | Since C99, it's been standard for printf and friends to accept a "z" size modifier, meaning "whatever size size_t has". Up to now we've generally dealt with printing size_t values by explicitly casting them to unsigned long and using the "l" modifier; but this is really the wrong thing on platforms where pointers are wider than longs (such as Win64). So let's start using "z" instead. To ensure we can do that on all platforms, teach src/port/snprintf.c to understand "z", and add a configure test to force use of that implementation when the platform's version doesn't handle "z". Having done that, modify a bunch of places that were using the unsigned-long hack to use "z" instead. This patch doesn't pretend to have gotten everyplace that could benefit, but it catches many of them. I made an effort in particular to ensure that all uses of the same error message text were updated together, so as not to increase the number of translatable strings. It's possible that this change will result in format-string warnings from pre-C99 compilers. We might have to reconsider if there are any popular compilers that will warn about this; but let's start by seeing what the buildfarm thinks. Andres Freund, with a little additional work by me
* Update copyright for 2014Bruce Momjian2014-01-07
| | | | | Update all files in head, and files COPYRIGHT and legal.sgml in all back branches.
* Don't include unused space in LOG_NEWPAGE records.Heikki Linnakangas2013-12-04
| | | | | This is the same trick we use when taking a full page image of a buffer passed to XLogInsert.
* Retry after buffer locking failure during SPGiST index creation.Tom Lane2013-11-02
| | | | | | | | | The original coding thought this case was impossible, but it can happen if the bgwriter or checkpointer processes decide to write out an index page while creation is still proceeding, leading to a bogus "unexpected spgdoinsert() failure" error. Problem reported by Jonathan S. Katz. Teodor Sigaev
* Typo fix.Robert Haas2013-09-18
| | | | Etsuro Fujita
* Avoid deadlocks during insertion into SP-GiST indexes.Tom Lane2013-06-14
| | | | | | | | | | | | | SP-GiST's original scheme for avoiding deadlocks during concurrent index insertions doesn't work, as per report from Hailong Li, and there isn't any evident way to make it work completely. We could possibly lock individual inner tuples instead of their whole pages, but preliminary experimentation suggests that the performance penalty would be huge. Instead, if we fail to get a buffer lock while descending the tree, just restart the tree descent altogether. We keep the old tuple positioning rules, though, in hopes of reducing the number of cases where this can happen. Teodor Sigaev, somewhat edited by Tom Lane
* pgindent run for release 9.3Bruce Momjian2013-05-29
| | | | | This is the first run of the Perl-based pgindent script. Also update pgindent instructions.
* Use the term "radix tree" instead of "suffix tree" for SP-GiST text opclass.Heikki Linnakangas2013-05-08
| | | | | | | What we have implemented is a radix tree (or a radix trie or a patricia trie), but the docs and code comments incorrectly called it a "suffix tree". Alexander Korotkov
* Allow I/O reliability checks using 16-bit checksumsSimon Riggs2013-03-22
| | | | | | | | | | | | | | | | | | | 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.
* Remove PageSetTLI and rename pd_tli to pd_checksumSimon Riggs2013-03-18
| | | | | | | | | | | | | | Remove use of PageSetTLI() from all page manipulation functions and adjust README to indicate change in the way we make changes to pages. Repurpose those bytes into the pd_checksum field and explain how that works in comments about page header. Refactoring ahead of actual feature patch which would make use of the checksum field, arriving later. Jeff Davis, with comments and doc changes by Simon Riggs Direction suggested by Robert Haas; many others providing review comments.
* Update copyrights for 2013Bruce Momjian2013-01-01
| | | | | Fully update git head, and update back branches in ./COPYRIGHT and legal.sgml files.
* Remove obsolete XLogRecPtr macrosAlvaro Herrera2012-12-28
| | | | | | | | | | | | | | | | | This gets rid of XLByteLT, XLByteLE, XLByteEQ and XLByteAdvance. These were useful for brevity when XLogRecPtrs were split in xlogid/xrecoff; but now that they are simple uint64's, they are just clutter. The only downside to making this change would be ease of backporting patches, but that has been negated by other substantive changes to the involved code anyway. The clarity of simpler expressions makes the change worthwhile. Most of the changes are mechanical, but in a couple of places, the patch author chose to invert the operator sense, making the code flow more logical (and more in line with preceding comments). Author: Andres Freund Eyeballed by Dimitri Fontaine and Alvaro Herrera
* Split out rmgr rm_desc functions into their own filesAlvaro Herrera2012-11-28
| | | | | This is necessary (but not sufficient) to have them compilable outside of a backend environment.
* Fix multiple problems in WAL replay.Tom Lane2012-11-12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Most of the replay functions for WAL record types that modify more than one page failed to ensure that those pages were locked correctly to ensure that concurrent queries could not see inconsistent page states. This is a hangover from coding decisions made long before Hot Standby was added, when it was hardly necessary to acquire buffer locks during WAL replay at all, let alone hold them for carefully-chosen periods. The key problem was that RestoreBkpBlocks was written to hold lock on each page restored from a full-page image for only as long as it took to update that page. This was guaranteed to break any WAL replay function in which there was any update-ordering constraint between pages, because even if the nominal order of the pages is the right one, any mixture of full-page and non-full-page updates in the same record would result in out-of-order updates. Moreover, it wouldn't work for situations where there's a requirement to maintain lock on one page while updating another. Failure to honor an update ordering constraint in this way is thought to be the cause of bug #7648 from Daniel Farina: what seems to have happened there is that a btree page being split was rewritten from a full-page image before the new right sibling page was written, and because lock on the original page was not maintained it was possible for hot standby queries to try to traverse the page's right-link to the not-yet-existing sibling page. To fix, get rid of RestoreBkpBlocks as such, and instead create a new function RestoreBackupBlock that restores just one full-page image at a time. This function can be invoked by WAL replay functions at the points where they would otherwise perform non-full-page updates; in this way, the physical order of page updates remains the same no matter which pages are replaced by full-page images. We can then further adjust the logic in individual replay functions if it is necessary to hold buffer locks for overlapping periods. A side benefit is that we can simplify the handling of concurrency conflict resolution by moving that code into the record-type-specfic functions; there's no more need to contort the code layout to keep conflict resolution in front of the RestoreBkpBlocks call. In connection with that, standardize on zero-based numbering rather than one-based numbering for referencing the full-page images. In HEAD, I removed the macros XLR_BKP_BLOCK_1 through XLR_BKP_BLOCK_4. They are still there in the header files in previous branches, but are no longer used by the code. In addition, fix some other bugs identified in the course of making these changes: spgRedoAddNode could fail to update the parent downlink at all, if the parent tuple is in the same page as either the old or new split tuple and we're not doing a full-page image: it would get fooled by the LSN having been advanced already. This would result in permanent index corruption, not just transient failure of concurrent queries. Also, ginHeapTupleFastInsert's "merge lists" case failed to mark the old tail page as a candidate for a full-page image; in the worst case this could result in torn-page corruption. heap_xlog_freeze() was inconsistent about using a cleanup lock or plain exclusive lock: it did the former in the normal path but the latter for a full-page image. A plain exclusive lock seems sufficient, so change to that. Also, remove gistRedoPageDeleteRecord(), which has been dead code since VACUUM FULL was rewritten. Back-patch to 9.0, where hot standby was introduced. Note however that 9.0 had a significantly different WAL-logging scheme for GIST index updates, and it doesn't appear possible to make that scheme safe for concurrent hot standby queries, because it can leave inconsistent states in the index even between WAL records. Given the lack of complaints from the field, we won't work too hard on fixing that branch.
* Trim spgist_private.h inclusionAlvaro Herrera2012-09-05
| | | | It doesn't really need rel.h; relcache.h is enough.
* Optimize SP-GiST insertions.Heikki Linnakangas2012-08-29
| | | | | | | This includes two micro-optimizations to the tight inner loop in descending the SP-GiST tree: 1. avoid an extra function call to index_getprocinfo when calling user-defined choose function, and 2. avoid a useless palloc+pfree when node labels are not used.
* Split heapam_xlog.h from heapam.hAlvaro Herrera2012-08-28
| | | | | | | | | | | | The heapam XLog functions are used by other modules, not all of which are interested in the rest of the heapam API. With this, we let them get just the XLog stuff in which they are interested and not pollute them with unrelated includes. Also, since heapam.h no longer requires xlog.h, many files that do include heapam.h no longer get xlog.h automatically, including a few headers. This is useful because heapam.h is getting pulled in by execnodes.h, which is in turn included by a lot of files.
* In SPGiST replay, do conflict resolution before modifying the page.Tom Lane2012-08-03
| | | | | | | | | In yesterday's commit 962e0cc71e839c58fb9125fa85511b8bbb8bdbee, I added the ResolveRecoveryConflictWithSnapshot call in the wrong place. I correctly put it before spgRedoVacuumRedirect itself would modify the index page --- but not before RestoreBkpBlocks, so replay of a record with a full-page image would modify the page before kicking off any conflicting HS transactions. Oops.
* Fix race conditions associated with SPGiST redirection tuples.Tom Lane2012-08-02
| | | | | | | | | | | | | | | The correct test for whether a redirection tuple is removable is whether tuple's xid < RecentGlobalXmin, not OldestXmin; the previous coding failed to protect index searches being done in concurrent transactions that have no XID. This mirrors the recent fix in btree's page recycling logic made in commit d3abbbebe52eb1e59e621c880ad57df9d40d13f2. Also, WAL-log the newest XID of any removed redirection tuple on an index page, and apply ResolveRecoveryConflictWithSnapshot during InHotStandby WAL replay. This protects against concurrent Hot Standby transactions possibly needing to see the redirection tuple(s). Per my query of 2012-03-12 and subsequent discussion.
* Assorted message style improvementsPeter Eisentraut2012-07-02
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* Cope with smaller-than-normal BLCKSZ setting in SPGiST indexes on text.Tom Lane2012-06-26
| | | | | | | | | | | | The original coding failed miserably for BLCKSZ of 4K or less, as reported by Josh Kupershmidt. With the present design for text indexes, a given inner tuple could have up to 256 labels (requiring either 3K or 4K bytes depending on MAXALIGN), which means that we can't positively guarantee no failures for smaller blocksizes. But we can at least make it behave sanely so long as there are few enough labels to fit on a page. Considering that btree is also more prone to "index tuple too large" failures when BLCKSZ is small, it's not clear that we should expend more work than this on this case.
* Replace int2/int4 in C code with int16/int32Peter Eisentraut2012-06-25
| | | | | | | | | | The latter was already the dominant use, and it's preferable because in C the convention is that intXX means XX bits. Therefore, allowing mixed use of int2, int4, int8, int16, int32 is obviously confusing. Remove the typedefs for int2 and int4 for now. They don't seem to be widely used outside of the PostgreSQL source tree, and the few uses can probably be cleaned up by the time this ships.
* Run pgindent on 9.2 source tree in preparation for first 9.3Bruce Momjian2012-06-10
| | | | commit-fest.
* Remove duplicate words in comments.Heikki Linnakangas2012-05-02
| | | | Found these with grep -r "for for ".
* Fix SPGiST vacuum algorithm to handle concurrent tuple motion properly.Tom Lane2012-03-12
| | | | | | | | | | | | | A leaf tuple that we need to delete could get moved as a consequence of an insertion happening concurrently with the VACUUM scan. If it moves from a page past the current scan point to a page before, we'll miss it, which is not acceptable. Hence, when we see a leaf-page REDIRECT that could have been made since our scan started, chase down the redirection pointer much as if we were doing a normal index search, and be sure to vacuum every page it leads to. This fixes the issue because, if the tuple was on page N at the instant we start our scan, we will surely find it as a consequence of chasing the redirect from page N, no matter how much it moves around in between. Problem noted by Takashi Yamamoto.
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