Function _rewrite_projections

src/ast/ast_rewrite_call_subquery.c:365–449

rewrites the projections of a Call {} clause, such that bound vars will remain in the record when passed to the CallSubquery op

// rewrites the projections of a Call {} clause, such that bound vars will
// remain in the record when passed to the CallSubquery op
static void _rewrite_projections
(
	cypher_astnode_t *wrapping_clause,  // outer-context clause (query/call {})
	uint clause_ind,                    // index of call {} clause in query
	uint start,                         // start ind of outer-scope bound vars
	char ***inter_names                 // internal representation of bound vars
) {
	//--------------------------------------------------------------------------
	// collect outer scope bound vars
	//--------------------------------------------------------------------------

	rax *outer_mapping = raxNew();
	if(start != clause_ind) {
		collect_aliases_in_scope(wrapping_clause, start, clause_ind,
			outer_mapping);
	}

	uint mapping_size = raxSize(outer_mapping);
	if(mapping_size == 0 && array_len(*inter_names) == 0) {
		raxFree(outer_mapping);
		return;
	}

	// create an array for the outer scope bound vars
	char **names = array_new(char *, mapping_size);

	_get_vars_inner_rep(outer_mapping, &names, inter_names);
	raxFree(outer_mapping);

	//--------------------------------------------------------------------------
	// transform relevant clauses
	//--------------------------------------------------------------------------

	// if there is a UNION clause in the subquery, each branch must be handled
	cypher_astnode_t *clause = (cypher_astnode_t *)
		cypher_ast_query_get_clause(wrapping_clause, clause_ind);
	cypher_astnode_t *subquery = cypher_ast_call_subquery_get_query(clause);
	AST ast = {0};
	ast.root = subquery;
	uint *union_indices = AST_GetClauseIndices(&ast, CYPHER_AST_UNION);
	uint clause_count = cypher_ast_query_nclauses(subquery);
	array_append(union_indices, clause_count);
	uint n_union_branches = array_len(union_indices);

	uint first_ind = 0;
	for(uint i = 0; i < n_union_branches; i++) {
		uint last_ind = union_indices[i];

		// check if first clause is a WITH clause
		const cypher_astnode_t *first_clause =
			cypher_ast_query_get_clause(subquery, first_ind);
		if(cypher_astnode_type(first_clause) == CYPHER_AST_WITH) {
			// replace first clause (WITH) with a WITH clause containing
			// "n->@n" projections for all bound vars in outer-scope context
			_replace_with_clause(clause, first_ind, names, *inter_names);
		} else {
			// add a leading WITH clause containing "n->@n" projections
			// for all bound vars (in outer-scope context)