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renecannaorenecannao
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feat: implement ARRAY subscript evaluation in expression evaluator
Replace the NODE_ARRAY_SUBSCRIPT stub with real evaluation logic that walks the ARRAY constructor's child nodes to retrieve the element at the given index. PostgreSQL uses 1-based indexing, MySQL uses 0-based. Out-of-bounds and NULL indices return null. Adds 9 tests covering both dialects, bounds checking, string elements, null index, and malformed nodes. Closes #19.
1 parent 31e4809 commit bdf10fc

2 files changed

Lines changed: 135 additions & 4 deletions

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‎include/sql_engine/expression_eval.h‎

Lines changed: 25 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -685,10 +685,31 @@ Value evaluate_expression(const AstNode* expr,
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}
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return value_null(); // no executor or no parsed child
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}
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case NodeType::NODE_TUPLE: return value_null(); // requires row/tuple value type
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case NodeType::NODE_ARRAY_CONSTRUCTOR: return value_null(); // requires array value type
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case NodeType::NODE_ARRAY_SUBSCRIPT: return value_null(); // requires array support
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case NodeType::NODE_FIELD_ACCESS: return value_null(); // requires composite type
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case NodeType::NODE_TUPLE: return value_null(); // Tuple as standalone value not supported
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case NodeType::NODE_ARRAY_CONSTRUCTOR: return value_null(); // Bare array without subscript
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case NodeType::NODE_ARRAY_SUBSCRIPT: {
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const AstNode* array_expr = expr->first_child;
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const AstNode* index_expr = array_expr ? array_expr->next_sibling : nullptr;
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if (!array_expr || !index_expr) return value_null();
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Value idx = evaluate_expression<D>(index_expr, resolve, functions, arena, subquery_exec);
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if (idx.is_null()) return value_null();
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int64_t i = idx.to_int64();
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if (array_expr->type == NodeType::NODE_ARRAY_CONSTRUCTOR) {
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// 1-based indexing for PostgreSQL, 0-based for MySQL
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int64_t pos = (D == sql_parser::Dialect::PostgreSQL) ? i - 1 : i;
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if (pos < 0) return value_null();
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const AstNode* child = array_expr->first_child;
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for (int64_t c = 0; c < pos && child; ++c) {
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child = child->next_sibling;
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}
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if (!child) return value_null();
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return evaluate_expression<D>(child, resolve, functions, arena, subquery_exec);
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}
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return value_null(); // Non-literal arrays not yet supported
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}
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case NodeType::NODE_FIELD_ACCESS: return value_null(); // Composite field access requires composite types
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default:
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return value_null(); // unknown node type

‎tests/test_expression_eval.cpp‎

Lines changed: 110 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -698,3 +698,113 @@ TEST_F(ExprEvalTest, ArrayConstructorReturnsNull) {
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AstNode* n = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
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EXPECT_TRUE(eval_mysql(n).is_null());
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}
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// ===== Array Subscript Evaluation =====
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TEST_F(ExprEvalTest, ArraySubscriptPg1Based) {
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// ARRAY[10, 20, 30][2] with PostgreSQL -> 20 (1-based)
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AstNode* arr = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "10"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "20"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "30"));
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AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
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subscript->add_child(arr);
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subscript->add_child(leaf(NodeType::NODE_LITERAL_INT, "2"));
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auto v = eval_pg(subscript);
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EXPECT_EQ(v.tag, Value::TAG_INT64);
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EXPECT_EQ(v.int_val, 20);
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}
719+
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TEST_F(ExprEvalTest, ArraySubscriptPgFirstElement) {
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// ARRAY[10, 20, 30][1] with PostgreSQL -> 10
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AstNode* arr = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "10"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "20"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "30"));
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AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
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subscript->add_child(arr);
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subscript->add_child(leaf(NodeType::NODE_LITERAL_INT, "1"));
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auto v = eval_pg(subscript);
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EXPECT_EQ(v.tag, Value::TAG_INT64);
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EXPECT_EQ(v.int_val, 10);
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}
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TEST_F(ExprEvalTest, ArraySubscriptOutOfBounds) {
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// ARRAY[10, 20][5] -> null
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AstNode* arr = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "10"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "20"));
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AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
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subscript->add_child(arr);
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subscript->add_child(leaf(NodeType::NODE_LITERAL_INT, "5"));
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EXPECT_TRUE(eval_pg(subscript).is_null());
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}
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TEST_F(ExprEvalTest, ArraySubscriptPgZeroOutOfBounds) {
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// ARRAY[10, 20][0] with PostgreSQL -> null (1-based, so 0 is out of bounds)
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AstNode* arr = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "10"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "20"));
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AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
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subscript->add_child(arr);
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subscript->add_child(leaf(NodeType::NODE_LITERAL_INT, "0"));
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EXPECT_TRUE(eval_pg(subscript).is_null());
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}
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TEST_F(ExprEvalTest, ArraySubscriptPgStringElements) {
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// ARRAY['hello', 'world'][1] with PostgreSQL -> 'hello'
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AstNode* arr = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
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arr->add_child(leaf(NodeType::NODE_LITERAL_STRING, "hello"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_STRING, "world"));
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AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
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subscript->add_child(arr);
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subscript->add_child(leaf(NodeType::NODE_LITERAL_INT, "1"));
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auto v = eval_pg(subscript);
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EXPECT_EQ(v.tag, Value::TAG_STRING);
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EXPECT_EQ(std::string(v.str_val.ptr, v.str_val.len), "hello");
775+
}
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TEST_F(ExprEvalTest, ArraySubscriptNullIndex) {
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// ARRAY[10, 20][NULL] -> null
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AstNode* arr = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
780+
arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "10"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "20"));
782+
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AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
784+
subscript->add_child(arr);
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subscript->add_child(make_node(arena, NodeType::NODE_LITERAL_NULL));
786+
787+
EXPECT_TRUE(eval_pg(subscript).is_null());
788+
}
789+
790+
TEST_F(ExprEvalTest, ArraySubscriptNoChildren) {
791+
// Malformed: no children -> null
792+
AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
793+
EXPECT_TRUE(eval_pg(subscript).is_null());
794+
}
795+
796+
TEST_F(ExprEvalTest, ArraySubscriptMysql0Based) {
797+
// MySQL uses 0-based indexing: ARRAY[10, 20, 30][0] -> 10
798+
AstNode* arr = make_node(arena, NodeType::NODE_ARRAY_CONSTRUCTOR);
799+
arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "10"));
800+
arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "20"));
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arr->add_child(leaf(NodeType::NODE_LITERAL_INT, "30"));
802+
803+
AstNode* subscript = make_node(arena, NodeType::NODE_ARRAY_SUBSCRIPT);
804+
subscript->add_child(arr);
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subscript->add_child(leaf(NodeType::NODE_LITERAL_INT, "0"));
806+
807+
auto v = eval_mysql(subscript);
808+
EXPECT_EQ(v.tag, Value::TAG_INT64);
809+
EXPECT_EQ(v.int_val, 10);
810+
}

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