Function _compress_clauses

src/ast/ast_rewrite_same_clauses.c:237–327

tries to compress clauses of a query or a foreach clause returns true if a rewrite occurred

// tries to compress clauses of a query or a foreach clause
// returns true if a rewrite occurred
static bool _compress_clauses
(
	const cypher_astnode_t *node  // node containing clauses to compress
) {
	bool rewritten = false;
	
	cypher_astnode_type_t type = cypher_astnode_type(node);

	ASSERT(type == CYPHER_AST_QUERY || type == CYPHER_AST_FOREACH);

	cypher_astnode_t **clauses = array_new(cypher_astnode_t *, 0);
	// is the node representing a FOREACH clause
	uint            clause_count  = 0;
	replace_func    replace_func  = NULL;
	get_clause_func get_clause    = NULL;
	// use appropriate function to get a positioned clause
	if(type == CYPHER_AST_FOREACH) {
		get_clause   = cypher_ast_foreach_get_clause;
		clause_count = cypher_ast_foreach_nclauses(node);
		replace_func = cypher_ast_foreach_replace_clauses;
	} else {
		get_clause   = cypher_ast_query_get_clause;
		replace_func = cypher_ast_query_replace_clauses;
		clause_count = cypher_ast_query_nclauses(node);
	}

	for(uint i = 0; i < clause_count; i++) {
		const cypher_astnode_t *clause = get_clause(node, i);
		cypher_astnode_type_t t = cypher_astnode_type(clause);

		// try compressing the inner-clauses of foreach clause and call subquery
		if(t == CYPHER_AST_FOREACH) {
			rewritten |= _compress_clauses(clause);
			continue;
		} else if(t == CYPHER_AST_CALL_SUBQUERY) {
			rewritten |=
				_compress_clauses(cypher_ast_call_subquery_get_query(clause));
			continue;
		}

		// check compressibility, move on if not compressible
		if(!is_compressible(clause, t)) {
			continue;
		}

		//----------------------------------------------------------------------
		// collect clauses of the same type as current clause
		//----------------------------------------------------------------------

		for (uint j = i; j < clause_count; j++) {
			clause = get_clause(node, j);
			cypher_astnode_type_t t2 = cypher_astnode_type(clause);
			if(t2 != t || !is_compressible(clause, t2)) {
				break;
			}
			array_append(clauses, (cypher_astnode_t *)clause);
		}