Function MultiExecBitmapAnd

src/backend/executor/nodeBitmapAnd.c:120–216

---------------------------------------------------------------- * MultiExecBitmapAnd * * BitmapAnd node gets the bitmaps generated from BitmapIndexScan * nodes and outputs a bitmap that ANDs all input bitmaps. * * The first input bitmap is utilized to store the result of the * AND and returned to the caller. In addition, the output points * to a newly created OpStream no

 * ----------------------------------------------------------------
 */
Node *
MultiExecBitmapAnd(BitmapAndState *node)
{
	PlanState **bitmapplans;
	int			nplans;
	int			i;
	bool		empty = false;
	TIDBitmap  *hbm = NULL;

	/* must provide our own instrumentation support */
	if (node->ps.instrument)
		InstrStartNode(node->ps.instrument);

	/*
	 * get information from the node
	 */
	bitmapplans = node->bitmapplans;
	nplans = node->nplans;

	/*
	 * Scan all the subplans and AND their result bitmaps
	 */
	for (i = 0; i < nplans; i++)
	{
		PlanState  *subnode = bitmapplans[i];
		Node		*subresult = NULL;

		subresult = MultiExecProcNode(subnode);

		if (!subresult || !(IsA(subresult, TIDBitmap) || IsA(subresult, StreamBitmap)))
			elog(ERROR, "unrecognized result from subplan");

		/*
		 * If this is a hash bitmap, intersect it now with other hash bitmaps.
		 * If we encounter some streamed bitmaps we'll add this hash bitmap
		 * as a stream to it.
		 */
		if (IsA(subresult, TIDBitmap))
		{
			/* first subplan that generates a hash bitmap */
			if (hbm == NULL)
				hbm = (TIDBitmap *) subresult;
			else
			{
				tbm_intersect(hbm, (TIDBitmap *)subresult);
				tbm_generic_free(subresult);
			}

			/*
			 * If at any stage we have a completely empty bitmap, we can fall out
			 * without evaluating the remaining subplans, since ANDing them can no
			 * longer change the result.  (Note: the fact that indxpath.c orders
			 * the subplans by selectivity should make this case more likely to
			 * occur.)
			 */
			if (tbm_is_empty(hbm))
			{
				empty = true;