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0bef1c0678
The principle behind the locking was not very well thought-out, and not documented. Add a section in the README to explain how it's supposed to work, and change the code so that it actually works that way. This fixes two bugs: 1. If fast update was turned on concurrently, subsequent inserts to the pending list would not conflict with predicate locks that were acquired earlier, on entry pages. The included 'predicate-gin-fastupdate' test demonstrates that. To fix, make all scans acquire a predicate lock on the metapage. That lock represents a scan of the pending list, whether or not there is a pending list at the moment. Forget about the optimization to skip locking/checking for locks, when fastupdate=off. 2. If a scan finds no match, it still needs to lock the entry page. The point of predicate locks is to lock the gabs between values, whether or not there is a match. The included 'predicate-gin-nomatch' test tests that case. In addition to those two bug fixes, this removes some unnecessary locking, following the principle laid out in the README. Because all items in a posting tree have the same key value, a lock on the posting tree root is enough to cover all the items. (With a very large posting tree, it would possibly be better to lock the posting tree leaf pages instead, so that a "skip scan" with a query like "A & B", you could avoid unnecessary conflict if a new tuple is inserted with A but !B. But let's keep this simple.) Also, some spelling fixes. Author: Heikki Linnakangas with some editorization by me Review: Andrey Borodin, Alexander Korotkov Discussion: https://www.postgresql.org/message-id/0b3ad2c2-2692-62a9-3a04-5724f2af9114@iki.fi |
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| .. | ||
| amapi.h | ||
| amvalidate.h | ||
| attnum.h | ||
| brin_internal.h | ||
| brin_page.h | ||
| brin_pageops.h | ||
| brin_revmap.h | ||
| brin_tuple.h | ||
| brin_xlog.h | ||
| brin.h | ||
| bufmask.h | ||
| clog.h | ||
| commit_ts.h | ||
| genam.h | ||
| generic_xlog.h | ||
| gin_private.h | ||
| gin.h | ||
| ginblock.h | ||
| ginxlog.h | ||
| gist_private.h | ||
| gist.h | ||
| gistscan.h | ||
| gistxlog.h | ||
| hash_xlog.h | ||
| hash.h | ||
| heapam_xlog.h | ||
| heapam.h | ||
| hio.h | ||
| htup_details.h | ||
| htup.h | ||
| itup.h | ||
| multixact.h | ||
| nbtree.h | ||
| nbtxlog.h | ||
| parallel.h | ||
| printsimple.h | ||
| printtup.h | ||
| reloptions.h | ||
| relscan.h | ||
| rewriteheap.h | ||
| rmgr.h | ||
| rmgrlist.h | ||
| sdir.h | ||
| session.h | ||
| skey.h | ||
| slru.h | ||
| spgist_private.h | ||
| spgist.h | ||
| spgxlog.h | ||
| stratnum.h | ||
| subtrans.h | ||
| sysattr.h | ||
| timeline.h | ||
| transam.h | ||
| tsmapi.h | ||
| tupconvert.h | ||
| tupdesc_details.h | ||
| tupdesc.h | ||
| tupmacs.h | ||
| tuptoaster.h | ||
| twophase_rmgr.h | ||
| twophase.h | ||
| valid.h | ||
| visibilitymap.h | ||
| xact.h | ||
| xlog_internal.h | ||
| xlog.h | ||
| xlogdefs.h | ||
| xloginsert.h | ||
| xlogreader.h | ||
| xlogrecord.h | ||
| xlogutils.h | ||