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Diffstat (limited to 'src/include/access/nbtxlog.h')
-rw-r--r-- | src/include/access/nbtxlog.h | 351 |
1 files changed, 351 insertions, 0 deletions
diff --git a/src/include/access/nbtxlog.h b/src/include/access/nbtxlog.h new file mode 100644 index 0000000..0f77318 --- /dev/null +++ b/src/include/access/nbtxlog.h @@ -0,0 +1,351 @@ +/*------------------------------------------------------------------------- + * + * nbtxlog.h + * header file for postgres btree xlog routines + * + * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * src/include/access/nbtxlog.h + * + *------------------------------------------------------------------------- + */ +#ifndef NBTXLOG_H +#define NBTXLOG_H + +#include "access/transam.h" +#include "access/xlogreader.h" +#include "lib/stringinfo.h" +#include "storage/off.h" + +/* + * XLOG records for btree operations + * + * XLOG allows to store some information in high 4 bits of log + * record xl_info field + */ +#define XLOG_BTREE_INSERT_LEAF 0x00 /* add index tuple without split */ +#define XLOG_BTREE_INSERT_UPPER 0x10 /* same, on a non-leaf page */ +#define XLOG_BTREE_INSERT_META 0x20 /* same, plus update metapage */ +#define XLOG_BTREE_SPLIT_L 0x30 /* add index tuple with split */ +#define XLOG_BTREE_SPLIT_R 0x40 /* as above, new item on right */ +#define XLOG_BTREE_INSERT_POST 0x50 /* add index tuple with posting split */ +#define XLOG_BTREE_DEDUP 0x60 /* deduplicate tuples for a page */ +#define XLOG_BTREE_DELETE 0x70 /* delete leaf index tuples for a page */ +#define XLOG_BTREE_UNLINK_PAGE 0x80 /* delete a half-dead page */ +#define XLOG_BTREE_UNLINK_PAGE_META 0x90 /* same, and update metapage */ +#define XLOG_BTREE_NEWROOT 0xA0 /* new root page */ +#define XLOG_BTREE_MARK_PAGE_HALFDEAD 0xB0 /* mark a leaf as half-dead */ +#define XLOG_BTREE_VACUUM 0xC0 /* delete entries on a page during + * vacuum */ +#define XLOG_BTREE_REUSE_PAGE 0xD0 /* old page is about to be reused from + * FSM */ +#define XLOG_BTREE_META_CLEANUP 0xE0 /* update cleanup-related data in the + * metapage */ + +/* + * All that we need to regenerate the meta-data page + */ +typedef struct xl_btree_metadata +{ + uint32 version; + BlockNumber root; + uint32 level; + BlockNumber fastroot; + uint32 fastlevel; + uint32 last_cleanup_num_delpages; + bool allequalimage; +} xl_btree_metadata; + +/* + * This is what we need to know about simple (without split) insert. + * + * This data record is used for INSERT_LEAF, INSERT_UPPER, INSERT_META, and + * INSERT_POST. Note that INSERT_META and INSERT_UPPER implies it's not a + * leaf page, while INSERT_POST and INSERT_LEAF imply that it must be a leaf + * page. + * + * Backup Blk 0: original page + * Backup Blk 1: child's left sibling, if INSERT_UPPER or INSERT_META + * Backup Blk 2: xl_btree_metadata, if INSERT_META + * + * Note: The new tuple is actually the "original" new item in the posting + * list split insert case (i.e. the INSERT_POST case). A split offset for + * the posting list is logged before the original new item. Recovery needs + * both, since it must do an in-place update of the existing posting list + * that was split as an extra step. Also, recovery generates a "final" + * newitem. See _bt_swap_posting() for details on posting list splits. + */ +typedef struct xl_btree_insert +{ + OffsetNumber offnum; + + /* POSTING SPLIT OFFSET FOLLOWS (INSERT_POST case) */ + /* NEW TUPLE ALWAYS FOLLOWS AT THE END */ +} xl_btree_insert; + +#define SizeOfBtreeInsert (offsetof(xl_btree_insert, offnum) + sizeof(OffsetNumber)) + +/* + * On insert with split, we save all the items going into the right sibling + * so that we can restore it completely from the log record. This way takes + * less xlog space than the normal approach, because if we did it standardly, + * XLogInsert would almost always think the right page is new and store its + * whole page image. The left page, however, is handled in the normal + * incremental-update fashion. + * + * Note: XLOG_BTREE_SPLIT_L and XLOG_BTREE_SPLIT_R share this data record. + * There are two variants to indicate whether the inserted tuple went into the + * left or right split page (and thus, whether the new item is stored or not). + * We always log the left page high key because suffix truncation can generate + * a new leaf high key using user-defined code. This is also necessary on + * internal pages, since the firstright item that the left page's high key was + * based on will have been truncated to zero attributes in the right page (the + * separator key is unavailable from the right page). + * + * Backup Blk 0: original page / new left page + * + * The left page's data portion contains the new item, if it's the _L variant. + * _R variant split records generally do not have a newitem (_R variant leaf + * page split records that must deal with a posting list split will include an + * explicit newitem, though it is never used on the right page -- it is + * actually an orignewitem needed to update existing posting list). The new + * high key of the left/original page appears last of all (and must always be + * present). + * + * Page split records that need the REDO routine to deal with a posting list + * split directly will have an explicit newitem, which is actually an + * orignewitem (the newitem as it was before the posting list split, not + * after). A posting list split always has a newitem that comes immediately + * after the posting list being split (which would have overlapped with + * orignewitem prior to split). Usually REDO must deal with posting list + * splits with an _L variant page split record, and usually both the new + * posting list and the final newitem go on the left page (the existing + * posting list will be inserted instead of the old, and the final newitem + * will be inserted next to that). However, _R variant split records will + * include an orignewitem when the split point for the page happens to have a + * lastleft tuple that is also the posting list being split (leaving newitem + * as the page split's firstright tuple). The existence of this corner case + * does not change the basic fact about newitem/orignewitem for the REDO + * routine: it is always state used for the left page alone. (This is why the + * record's postingoff field isn't a reliable indicator of whether or not a + * posting list split occurred during the page split; a non-zero value merely + * indicates that the REDO routine must reconstruct a new posting list tuple + * that is needed for the left page.) + * + * This posting list split handling is equivalent to the xl_btree_insert REDO + * routine's INSERT_POST handling. While the details are more complicated + * here, the concept and goals are exactly the same. See _bt_swap_posting() + * for details on posting list splits. + * + * Backup Blk 1: new right page + * + * The right page's data portion contains the right page's tuples in the form + * used by _bt_restore_page. This includes the new item, if it's the _R + * variant. The right page's tuples also include the right page's high key + * with either variant (moved from the left/original page during the split), + * unless the split happened to be of the rightmost page on its level, where + * there is no high key for new right page. + * + * Backup Blk 2: next block (orig page's rightlink), if any + * Backup Blk 3: child's left sibling, if non-leaf split + */ +typedef struct xl_btree_split +{ + uint32 level; /* tree level of page being split */ + OffsetNumber firstrightoff; /* first origpage item on rightpage */ + OffsetNumber newitemoff; /* new item's offset */ + uint16 postingoff; /* offset inside orig posting tuple */ +} xl_btree_split; + +#define SizeOfBtreeSplit (offsetof(xl_btree_split, postingoff) + sizeof(uint16)) + +/* + * When page is deduplicated, consecutive groups of tuples with equal keys are + * merged together into posting list tuples. + * + * The WAL record represents a deduplication pass for a leaf page. An array + * of BTDedupInterval structs follows. + */ +typedef struct xl_btree_dedup +{ + uint16 nintervals; + + /* DEDUPLICATION INTERVALS FOLLOW */ +} xl_btree_dedup; + +#define SizeOfBtreeDedup (offsetof(xl_btree_dedup, nintervals) + sizeof(uint16)) + +/* + * This is what we need to know about page reuse within btree. This record + * only exists to generate a conflict point for Hot Standby. + * + * Note that we must include a RelFileNode in the record because we don't + * actually register the buffer with the record. + */ +typedef struct xl_btree_reuse_page +{ + RelFileNode node; + BlockNumber block; + FullTransactionId latestRemovedFullXid; +} xl_btree_reuse_page; + +#define SizeOfBtreeReusePage (sizeof(xl_btree_reuse_page)) + +/* + * xl_btree_vacuum and xl_btree_delete records describe deletion of index + * tuples on a leaf page. The former variant is used by VACUUM, while the + * latter variant is used by the ad-hoc deletions that sometimes take place + * when btinsert() is called. + * + * The records are very similar. The only difference is that xl_btree_delete + * has to include a latestRemovedXid field to generate recovery conflicts. + * (VACUUM operations can just rely on earlier conflicts generated during + * pruning of the table whose TIDs the to-be-deleted index tuples point to. + * There are also small differences between each REDO routine that we don't go + * into here.) + * + * xl_btree_vacuum and xl_btree_delete both represent deletion of any number + * of index tuples on a single leaf page using page offset numbers. Both also + * support "updates" of index tuples, which is how deletes of a subset of TIDs + * contained in an existing posting list tuple are implemented. + * + * Updated posting list tuples are represented using xl_btree_update metadata. + * The REDO routines each use the xl_btree_update entries (plus each + * corresponding original index tuple from the target leaf page) to generate + * the final updated tuple. + * + * Updates are only used when there will be some remaining TIDs left by the + * REDO routine. Otherwise the posting list tuple just gets deleted outright. + */ +typedef struct xl_btree_vacuum +{ + uint16 ndeleted; + uint16 nupdated; + + /* DELETED TARGET OFFSET NUMBERS FOLLOW */ + /* UPDATED TARGET OFFSET NUMBERS FOLLOW */ + /* UPDATED TUPLES METADATA (xl_btree_update) ARRAY FOLLOWS */ +} xl_btree_vacuum; + +#define SizeOfBtreeVacuum (offsetof(xl_btree_vacuum, nupdated) + sizeof(uint16)) + +typedef struct xl_btree_delete +{ + TransactionId latestRemovedXid; + uint16 ndeleted; + uint16 nupdated; + + /* DELETED TARGET OFFSET NUMBERS FOLLOW */ + /* UPDATED TARGET OFFSET NUMBERS FOLLOW */ + /* UPDATED TUPLES METADATA (xl_btree_update) ARRAY FOLLOWS */ +} xl_btree_delete; + +#define SizeOfBtreeDelete (offsetof(xl_btree_delete, nupdated) + sizeof(uint16)) + +/* + * The offsets that appear in xl_btree_update metadata are offsets into the + * original posting list from tuple, not page offset numbers. These are + * 0-based. The page offset number for the original posting list tuple comes + * from the main xl_btree_vacuum/xl_btree_delete record. + */ +typedef struct xl_btree_update +{ + uint16 ndeletedtids; + + /* POSTING LIST uint16 OFFSETS TO A DELETED TID FOLLOW */ +} xl_btree_update; + +#define SizeOfBtreeUpdate (offsetof(xl_btree_update, ndeletedtids) + sizeof(uint16)) + +/* + * This is what we need to know about marking an empty subtree for deletion. + * The target identifies the tuple removed from the parent page (note that we + * remove this tuple's downlink and the *following* tuple's key). Note that + * the leaf page is empty, so we don't need to store its content --- it is + * just reinitialized during recovery using the rest of the fields. + * + * Backup Blk 0: leaf block + * Backup Blk 1: top parent + */ +typedef struct xl_btree_mark_page_halfdead +{ + OffsetNumber poffset; /* deleted tuple id in parent page */ + + /* information needed to recreate the leaf page: */ + BlockNumber leafblk; /* leaf block ultimately being deleted */ + BlockNumber leftblk; /* leaf block's left sibling, if any */ + BlockNumber rightblk; /* leaf block's right sibling */ + BlockNumber topparent; /* topmost internal page in the subtree */ +} xl_btree_mark_page_halfdead; + +#define SizeOfBtreeMarkPageHalfDead (offsetof(xl_btree_mark_page_halfdead, topparent) + sizeof(BlockNumber)) + +/* + * This is what we need to know about deletion of a btree page. Note that we + * only leave behind a small amount of bookkeeping information in deleted + * pages (deleted pages must be kept around as tombstones for a while). It is + * convenient for the REDO routine to regenerate its target page from scratch. + * This is why WAL record describes certain details that are actually directly + * available from the target page. + * + * Backup Blk 0: target block being deleted + * Backup Blk 1: target block's left sibling, if any + * Backup Blk 2: target block's right sibling + * Backup Blk 3: leaf block (if different from target) + * Backup Blk 4: metapage (if rightsib becomes new fast root) + */ +typedef struct xl_btree_unlink_page +{ + BlockNumber leftsib; /* target block's left sibling, if any */ + BlockNumber rightsib; /* target block's right sibling */ + uint32 level; /* target block's level */ + FullTransactionId safexid; /* target block's BTPageSetDeleted() XID */ + + /* + * Information needed to recreate a half-dead leaf page with correct + * topparent link. The fields are only used when deletion operation's + * target page is an internal page. REDO routine creates half-dead page + * from scratch to keep things simple (this is the same convenient + * approach used for the target page itself). + */ + BlockNumber leafleftsib; + BlockNumber leafrightsib; + BlockNumber leaftopparent; /* next child down in the subtree */ + + /* xl_btree_metadata FOLLOWS IF XLOG_BTREE_UNLINK_PAGE_META */ +} xl_btree_unlink_page; + +#define SizeOfBtreeUnlinkPage (offsetof(xl_btree_unlink_page, leaftopparent) + sizeof(BlockNumber)) + +/* + * New root log record. There are zero tuples if this is to establish an + * empty root, or two if it is the result of splitting an old root. + * + * Note that although this implies rewriting the metadata page, we don't need + * an xl_btree_metadata record --- the rootblk and level are sufficient. + * + * Backup Blk 0: new root page (2 tuples as payload, if splitting old root) + * Backup Blk 1: left child (if splitting an old root) + * Backup Blk 2: metapage + */ +typedef struct xl_btree_newroot +{ + BlockNumber rootblk; /* location of new root (redundant with blk 0) */ + uint32 level; /* its tree level */ +} xl_btree_newroot; + +#define SizeOfBtreeNewroot (offsetof(xl_btree_newroot, level) + sizeof(uint32)) + + +/* + * prototypes for functions in nbtxlog.c + */ +extern void btree_redo(XLogReaderState *record); +extern void btree_desc(StringInfo buf, XLogReaderState *record); +extern const char *btree_identify(uint8 info); +extern void btree_xlog_startup(void); +extern void btree_xlog_cleanup(void); +extern void btree_mask(char *pagedata, BlockNumber blkno); + +#endif /* NBTXLOG_H */ |