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Revamp the WAL record format.
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.
This commit is contained in:
Heikki Linnakangas
@ -17,7 +17,7 @@
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#include "access/genam.h"
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#include "access/itup.h"
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#include "access/sdir.h"
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#include "access/xlogrecord.h"
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#include "access/xlogreader.h"
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#include "catalog/pg_index.h"
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#include "lib/stringinfo.h"
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#include "storage/bufmgr.h"
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@ -227,15 +227,6 @@ typedef struct BTMetaPageData
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#define XLOG_BTREE_REUSE_PAGE 0xD0 /* old page is about to be reused from
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* FSM */
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/*
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* All that we need to find changed index tuple
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*/
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typedef struct xl_btreetid
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{
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RelFileNode node;
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ItemPointerData tid; /* changed tuple id */
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} xl_btreetid;
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/*
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* All that we need to regenerate the meta-data page
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*/
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@ -252,16 +243,17 @@ typedef struct xl_btree_metadata
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*
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* This data record is used for INSERT_LEAF, INSERT_UPPER, INSERT_META.
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* Note that INSERT_META implies it's not a leaf page.
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*
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* Backup Blk 0: original page (data contains the inserted tuple)
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* Backup Blk 1: child's left sibling, if INSERT_UPPER or INSERT_META
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* Backup Blk 2: xl_btree_metadata, if INSERT_META
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*/
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typedef struct xl_btree_insert
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{
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xl_btreetid target; /* inserted tuple id */
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/* BlockNumber finishes_split field FOLLOWS IF NOT XLOG_BTREE_INSERT_LEAF */
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/* xl_btree_metadata FOLLOWS IF XLOG_BTREE_INSERT_META */
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/* INDEX TUPLE FOLLOWS AT END OF STRUCT */
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OffsetNumber offnum;
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} xl_btree_insert;
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#define SizeOfBtreeInsert (offsetof(xl_btreetid, tid) + SizeOfIptrData)
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#define SizeOfBtreeInsert (offsetof(xl_btree_insert, offnum) + sizeof(OffsetNumber))
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/*
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* On insert with split, we save all the items going into the right sibling
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@ -278,45 +270,41 @@ typedef struct xl_btree_insert
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* the root page, and thus that a newroot record rather than an insert or
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* split record should follow. Note that a split record never carries a
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* metapage update --- we'll do that in the parent-level update.
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*
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* Backup Blk 0: original page / new left page
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*
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* The left page's data portion contains the new item, if it's the _L variant.
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* (In the _R variants, the new item is one of the right page's tuples.)
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* If level > 0, an IndexTuple representing the HIKEY of the left page
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* follows. We don't need this on leaf pages, because it's the same as the
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* leftmost key in the new right page.
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*
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* Backup Blk 1: new right page
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*
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* The right page's data portion contains the right page's tuples in the
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* form used by _bt_restore_page.
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*
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* Backup Blk 2: next block (orig page's rightlink), if any
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* Backup Blk 3: child's left sibling, if non-leaf split
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*/
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typedef struct xl_btree_split
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{
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RelFileNode node;
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BlockNumber leftsib; /* orig page / new left page */
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BlockNumber rightsib; /* new right page */
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BlockNumber rnext; /* next block (orig page's rightlink) */
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uint32 level; /* tree level of page being split */
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OffsetNumber firstright; /* first item moved to right page */
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/*
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* In the _L variants, next are OffsetNumber newitemoff and the new item.
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* (In the _R variants, the new item is one of the right page's tuples.)
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* The new item, but not newitemoff, is suppressed if XLogInsert chooses
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* to store the left page's whole page image.
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*
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* If level > 0, an IndexTuple representing the HIKEY of the left page
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* follows. We don't need this on leaf pages, because it's the same as
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* the leftmost key in the new right page. Also, it's suppressed if
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* XLogInsert chooses to store the left page's whole page image.
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*
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* If level > 0, BlockNumber of the page whose incomplete-split flag this
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* insertion clears. (not aligned)
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*
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* Last are the right page's tuples in the form used by _bt_restore_page.
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*/
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OffsetNumber newitemoff; /* new item's offset (if placed on left page) */
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} xl_btree_split;
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#define SizeOfBtreeSplit (offsetof(xl_btree_split, firstright) + sizeof(OffsetNumber))
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#define SizeOfBtreeSplit (offsetof(xl_btree_split, newitemoff) + sizeof(OffsetNumber))
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/*
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* This is what we need to know about delete of individual leaf index tuples.
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* The WAL record can represent deletion of any number of index tuples on a
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* single index page when *not* executed by VACUUM.
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*
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* Backup Blk 0: index page
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*/
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typedef struct xl_btree_delete
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{
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RelFileNode node; /* RelFileNode of the index */
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BlockNumber block;
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RelFileNode hnode; /* RelFileNode of the heap the index currently
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* points at */
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int nitems;
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@ -361,8 +349,6 @@ typedef struct xl_btree_reuse_page
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*/
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typedef struct xl_btree_vacuum
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{
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RelFileNode node;
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BlockNumber block;
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BlockNumber lastBlockVacuumed;
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/* TARGET OFFSET NUMBERS FOLLOW */
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@ -376,10 +362,13 @@ typedef struct xl_btree_vacuum
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* remove this tuple's downlink and the *following* tuple's key). Note that
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* the leaf page is empty, so we don't need to store its content --- it is
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* just reinitialized during recovery using the rest of the fields.
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*
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* Backup Blk 0: leaf block
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* Backup Blk 1: top parent
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*/
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typedef struct xl_btree_mark_page_halfdead
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{
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xl_btreetid target; /* deleted tuple id in parent page */
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OffsetNumber poffset; /* deleted tuple id in parent page */
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/* information needed to recreate the leaf page: */
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BlockNumber leafblk; /* leaf block ultimately being deleted */
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@ -394,11 +383,15 @@ typedef struct xl_btree_mark_page_halfdead
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* This is what we need to know about deletion of a btree page. Note we do
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* not store any content for the deleted page --- it is just rewritten as empty
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* during recovery, apart from resetting the btpo.xact.
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*
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* Backup Blk 0: target block being deleted
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* Backup Blk 1: target block's left sibling, if any
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* Backup Blk 2: target block's right sibling
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* Backup Blk 3: leaf block (if different from target)
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* Backup Blk 4: metapage (if rightsib becomes new fast root)
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*/
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typedef struct xl_btree_unlink_page
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{
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RelFileNode node;
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BlockNumber deadblk; /* target block being deleted */
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BlockNumber leftsib; /* target block's left sibling, if any */
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BlockNumber rightsib; /* target block's right sibling */
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@ -406,7 +399,6 @@ typedef struct xl_btree_unlink_page
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* Information needed to recreate the leaf page, when target is an
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* internal page.
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*/
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BlockNumber leafblk;
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BlockNumber leafleftsib;
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BlockNumber leafrightsib;
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BlockNumber topparent; /* next child down in the branch */
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@ -423,13 +415,15 @@ typedef struct xl_btree_unlink_page
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*
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* Note that although this implies rewriting the metadata page, we don't need
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* an xl_btree_metadata record --- the rootblk and level are sufficient.
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*
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* Backup Blk 0: new root page (2 tuples as payload, if splitting old root)
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* Backup Blk 1: left child (if splitting an old root)
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* Backup Blk 2: metapage
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*/
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typedef struct xl_btree_newroot
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{
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RelFileNode node;
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BlockNumber rootblk; /* location of new root */
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BlockNumber rootblk; /* location of new root (redundant with blk 0) */
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uint32 level; /* its tree level */
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/* 0 or 2 INDEX TUPLES FOLLOW AT END OF STRUCT */
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} xl_btree_newroot;
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#define SizeOfBtreeNewroot (offsetof(xl_btree_newroot, level) + sizeof(uint32))
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@ -726,8 +720,8 @@ extern void _bt_leafbuild(BTSpool *btspool, BTSpool *spool2);
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/*
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* prototypes for functions in nbtxlog.c
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*/
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extern void btree_redo(XLogRecPtr lsn, XLogRecord *record);
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extern void btree_desc(StringInfo buf, XLogRecord *record);
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extern void btree_redo(XLogReaderState *record);
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extern void btree_desc(StringInfo buf, XLogReaderState *record);
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extern const char *btree_identify(uint8 info);
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#endif /* NBTREE_H */
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