Function _replace_match_clause

src/ast/ast_rewrite_same_clauses.c:64–120

compresses multiple consecutive MATCH clauses into a single MATCH clause

// compresses multiple consecutive MATCH clauses into a single MATCH clause
static void _replace_match_clause
(
	cypher_astnode_t *root,      // ast root
	cypher_astnode_t **clauses,  // clause being replaced
	int scope_start,             // beginning of scope
	int scope_end,               // ending of scope
	replace_func replace         // replace function pointer
) {
	uint count = array_len(clauses);

	cypher_astnode_t *predicate = NULL;
	struct cypher_input_range range = cypher_astnode_range(clauses[0]);
	cypher_astnode_t **paths = array_new(cypher_astnode_t *, count);

	// collect MATCH patterns and predicates
	for (uint i = 0; i < count; i++) {
		const cypher_astnode_t *pattern =
			cypher_ast_match_get_pattern(clauses[i]);
		uint npaths = cypher_ast_pattern_npaths(pattern);

		for (uint j = 0; j < npaths; j++) {
			const cypher_astnode_t *path =
				cypher_ast_pattern_get_path(pattern, j);
			array_append(paths, cypher_ast_clone(path));	
		}

		// combine MATCH predicates into a single predicate using AND connectors
		cypher_astnode_t *new_predicate =
			(cypher_astnode_t *)cypher_ast_match_get_predicate(clauses[i]);
		if(new_predicate != NULL) {
			new_predicate = cypher_ast_clone(new_predicate);
			if(predicate == NULL) {
				predicate = new_predicate;
			} else {
				// concat using AND
				cypher_astnode_t *children[] = {predicate, new_predicate};
				predicate = cypher_ast_binary_operator(CYPHER_OP_AND, predicate,
						new_predicate, children, 2, range);
			}
		}
	}
	
	// build the replacement pattern
	cypher_astnode_t *pattern =
		cypher_ast_pattern(paths, array_len(paths), paths, array_len(paths),
				range);
	
	// build the replacement clause
	cypher_astnode_t *children[] = {pattern, predicate};
	cypher_astnode_t *new_clause = cypher_ast_match(false, pattern, NULL, 0,
			predicate, children, predicate == NULL ? 1 : 2, range);

	// replace original clause with the new one
	replace(root, new_clause, scope_start, scope_end);
	
	array_free(paths);
}