128 lines
2.5 KiB
C
128 lines
2.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* datapagemap.c
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* A data structure for keeping track of data pages that have changed.
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*
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* This is a fairly simple bitmap.
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*
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* Copyright (c) 2013-2019, PostgreSQL Global Development Group
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres_fe.h"
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#include "common/logging.h"
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#include "datapagemap.h"
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struct datapagemap_iterator
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{
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datapagemap_t *map;
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BlockNumber nextblkno;
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};
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/*****
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* Public functions
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*/
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/*
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* Add a block to the bitmap.
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*/
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void
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datapagemap_add(datapagemap_t *map, BlockNumber blkno)
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{
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int offset;
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int bitno;
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offset = blkno / 8;
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bitno = blkno % 8;
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/* enlarge or create bitmap if needed */
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if (map->bitmapsize <= offset)
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{
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int oldsize = map->bitmapsize;
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int newsize;
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/*
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* The minimum to hold the new bit is offset + 1. But add some
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* headroom, so that we don't need to repeatedly enlarge the bitmap in
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* the common case that blocks are modified in order, from beginning
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* of a relation to the end.
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*/
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newsize = offset + 1;
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newsize += 10;
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map->bitmap = pg_realloc(map->bitmap, newsize);
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/* zero out the newly allocated region */
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memset(&map->bitmap[oldsize], 0, newsize - oldsize);
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map->bitmapsize = newsize;
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}
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/* Set the bit */
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map->bitmap[offset] |= (1 << bitno);
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}
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/*
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* Start iterating through all entries in the page map.
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*
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* After datapagemap_iterate, call datapagemap_next to return the entries,
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* until it returns false. After you're done, use pg_free() to destroy the
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* iterator.
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*/
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datapagemap_iterator_t *
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datapagemap_iterate(datapagemap_t *map)
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{
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datapagemap_iterator_t *iter;
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iter = pg_malloc(sizeof(datapagemap_iterator_t));
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iter->map = map;
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iter->nextblkno = 0;
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return iter;
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}
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bool
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datapagemap_next(datapagemap_iterator_t *iter, BlockNumber *blkno)
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{
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datapagemap_t *map = iter->map;
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for (;;)
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{
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BlockNumber blk = iter->nextblkno;
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int nextoff = blk / 8;
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int bitno = blk % 8;
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if (nextoff >= map->bitmapsize)
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break;
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iter->nextblkno++;
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if (map->bitmap[nextoff] & (1 << bitno))
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{
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*blkno = blk;
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return true;
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}
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}
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/* no more set bits in this bitmap. */
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return false;
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}
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/*
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* A debugging aid. Prints out the contents of the page map.
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*/
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void
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datapagemap_print(datapagemap_t *map)
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{
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datapagemap_iterator_t *iter;
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BlockNumber blocknum;
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iter = datapagemap_iterate(map);
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while (datapagemap_next(iter, &blocknum))
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pg_log_debug("block %u", blocknum);
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pg_free(iter);
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}
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