Function blgetbitmap

contrib/bloom/blscan.c:80–190

* Insert all matching tuples into a bitmap. */

 * Insert all matching tuples into a bitmap.
 */
int64
blgetbitmap(IndexScanDesc scan, Node **bmNodeP)
{
	int64		ntids = 0;
	BlockNumber blkno = BLOOM_HEAD_BLKNO,
				npages;
	int			i;
	TIDBitmap  *tbm;
	BufferAccessStrategy bas;
	BloomScanOpaque so = (BloomScanOpaque) scan->opaque;

	/*
	 * GPDB specific code. Since GPDB also support StreamBitmap
	 * in bitmap index. So normally we need to create specific bitmap
	 * node in the amgetbitmap AM.
	 */
	Assert(bmNodeP);
	if (*bmNodeP == NULL)
	{
		/* XXX should we use less than work_mem for this? */
		tbm = tbm_create(work_mem * 1024L, scan->dsa);
		*bmNodeP = (Node *) tbm;
	}
	else if (!IsA(*bmNodeP, TIDBitmap))
		elog(ERROR, "non bloom bitmap");
	else
		tbm = (TIDBitmap *)*bmNodeP;

	if (so->sign == NULL)
	{
		/* New search: have to calculate search signature */
		ScanKey		skey = scan->keyData;

		so->sign = palloc0(sizeof(BloomSignatureWord) * so->state.opts.bloomLength);

		for (i = 0; i < scan->numberOfKeys; i++)
		{
			/*
			 * Assume bloom-indexable operators to be strict, so nothing could
			 * be found for NULL key.
			 */
			if (skey->sk_flags & SK_ISNULL)
			{
				pfree(so->sign);
				so->sign = NULL;
				return 0;
			}

			/* Add next value to the signature */
			signValue(&so->state, so->sign, skey->sk_argument,
					  skey->sk_attno - 1);

			skey++;
		}
	}

	/*
	 * We're going to read the whole index. This is why we use appropriate