Function SQE_select

src/gpre/sqe.cpp:1089–1166

//

gpre_rse* SQE_select(gpre_req* request, bool view_flag)
{
	gpre_lls* context_stack = NULL;
	gpre_ctx* context = 0;
	bool have_union = false;

	assert_IS_REQ(request);

	map* const old_map = request->req_map;

	// Get components of union.  Most likely there isn't one, so this is
	// probably wasted work.

	gpre_rse* select = NULL;
	gpre_rse* rse1 = NULL;
	select = rse1 = par_select(request, NULL);

	// "Look for ... the UNION label ... "
	while (MSC_match(KW_UNION))
	{
		have_union = true;
		const bool union_all = MSC_match(KW_ALL);
		if (!MSC_match(KW_SELECT))
			CPR_s_error("SELECT");

		MSC_push((gpre_nod*) request->req_contexts, &context_stack);
		request->req_contexts = NULL;
		request->req_map = NULL;
		gpre_rse* rse2 = par_select(request, rse1);

		// We've got a bona fide union.  Make a union node to hold sub-rse
		// and then a new rse to point to it.

		select = (gpre_rse*) MSC_alloc(RSE_LEN(1));
		select->rse_context[0] = context = MSC_context(request);
		gpre_nod* node = MSC_node(nod_union, 2);
		select->rse_union = node;
		node->nod_arg[0] = (gpre_nod*) rse1;
		node->nod_arg[1] = (gpre_nod*) rse2;

		map* new_map = (map*) MSC_alloc(sizeof(map));
		rse1->rse_map = new_map;
		new_map->map_context = context;
		select->rse_fields = post_select_list(rse1->rse_fields, new_map);

		rse2->rse_map = new_map = (map*) MSC_alloc(sizeof(map));
		new_map->map_context = context;
		post_select_list(rse2->rse_fields, new_map);

		select->rse_into = rse1->rse_into;
		if (!union_all)
			select->rse_reduced = select->rse_fields;

		// Result of this UNION might be the left side of the NEXT UNION
		rse1 = select;
	}

	// Restore the context lists that were forgotten