Function _bitmap_init

src/backend/access/bitmap/bitmappages.c:364–453

* _bitmap_init() -- initialize the bitmap index. * * Create the meta page, a new heap which stores the distinct values for * the attributes to be indexed, a btree index on this new heap for searching * those distinct values, and the first LOV page. * * for_empty: true means build for '_init' file. * Create bitmap index for a 'unlogged' table will call bmbuildempty(), which * initialize the

 * new heap and its index from meta page through GetBitmapIndexAuxOids().
 */
void
_bitmap_init(Relation indexrel, bool use_wal, bool for_empty)
{
	BMMetaPage		metapage;
	Buffer			metabuf;
	Page			page;
	Buffer			buf;
	BMLOVItem 		lovItem;
	OffsetNumber	newOffset;
	Page			currLovPage;
	OffsetNumber	o;
	Oid			lovHeapOid;
	Oid			lovIndexOid;
	ForkNumber	fork;

	fork = for_empty ?  INIT_FORKNUM : MAIN_FORKNUM;

	/* sanity check */
	if (RelationGetNumberOfBlocksInFork(indexrel, fork) != 0)
		ereport(ERROR,
				(errcode(ERRCODE_INDEX_CORRUPTED),
				errmsg("cannot initialize non-empty bitmap index \"%s\"",
				RelationGetRelationName(indexrel))));

	/* create the metapage */
	metabuf = ReadBufferExtended(indexrel, fork, P_NEW, RBM_NORMAL, NULL);
	LockBuffer(metabuf, BUFFER_LOCK_EXCLUSIVE);
	page = BufferGetPage(metabuf);
	Assert(PageIsNew(page));

	/* initialize the LOV metadata */
	if (for_empty)
		GetBitmapIndexAuxOids(indexrel, &lovHeapOid, &lovIndexOid);
	else
		_bitmap_create_lov_heapandindex(indexrel, &lovHeapOid, &lovIndexOid);

	START_CRIT_SECTION();

	MarkBufferDirty(metabuf);

	/* initialize the metapage */
	PageInit(page, BufferGetPageSize(metabuf), 0);
	metapage = (BMMetaPage) PageGetContents(page);
	
	metapage->bm_magic = BITMAP_MAGIC;
	metapage->bm_version = BITMAP_VERSION;
	metapage->bm_lov_heapId = lovHeapOid;
	metapage->bm_lov_indexId = lovIndexOid;

	if (use_wal)
		_bitmap_log_metapage(indexrel, fork, page);

	/* allocate the first LOV page. */
	buf = ReadBufferExtended(indexrel, fork, P_NEW, RBM_NORMAL, NULL);
	LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
	_bitmap_init_lovpage(indexrel, buf);

	MarkBufferDirty(buf);