Allow NULL values in IN clause tuple literal formatting

When formatting IN clauses like `i in (1, 3, NULL)`, the list can now be
combined into a compact tuple literal format when it contains a mix of:
- Numeric values + NULLs
- String values + NULLs

Previously, the presence of NULL would force the verbose Function tuple
format. Now `in (1, 3, NULL)` correctly outputs `Literal Tuple_(UInt64_1, UInt64_3, NULL)`.

Fixes all 16 statements in 01231_operator_null_in and many statements in:
- 00441_nulls_in
- 00939_test_null_in
- 01410_nullable_key_and_index
- 01507_transform_null_in
- 01558_transform_null_in
- 01756_optimize_skip_unused_shards_rewrite_in
- 02499_analyzer_aggregate_function_lambda_crash_fix
- 03234_evaluate_constant_analyzer
- 03393_non_constant_second_argument_for_in
- 03578_kv_in_type_casts

Author: claude

internal/explain/functions.go

@@ -659,22 +659,28 @@ func explainInExpr(sb *strings.Builder, n *ast.InExpr, indent string, depth int)
 
 	// Determine if the IN list should be combined into a single tuple literal
 	// This happens when we have multiple literals of compatible types:
-	// - All numeric literals/expressions (integers/floats, including unary minus)
-	// - All string literals
+	// - All numeric literals/expressions (integers/floats, including unary minus) + NULLs
+	// - All string literals + NULLs
 	// - All tuple literals that contain only primitive literals (recursively)
 	canBeTupleLiteral := false
 	if n.Query == nil && len(n.List) > 1 {
-		allNumeric := true
-		allStrings := true
+		allNumericOrNull := true
+		allStringsOrNull := true
 		allTuples := true
 		allTuplesArePrimitive := true
+		hasNonNull := false // Need at least one non-null value
 		for _, item := range n.List {
 			if lit, ok := item.(*ast.Literal); ok {
+				if lit.Type == ast.LiteralNull {
+					// NULL is compatible with both numeric and string lists
+					continue
+				}
+				hasNonNull = true
 				if lit.Type != ast.LiteralInteger && lit.Type != ast.LiteralFloat {
-					allNumeric = false
+					allNumericOrNull = false
 				}
 				if lit.Type != ast.LiteralString {
-					allStrings = false
+					allStringsOrNull = false
 				}
 				if lit.Type != ast.LiteralTuple {
 					allTuples = false
@@ -686,17 +692,18 @@ func explainInExpr(sb *strings.Builder, n *ast.InExpr, indent string, depth int)
 				}
 			} else if isNumericExpr(item) {
 				// Unary minus of numeric is still numeric
-				allStrings = false
+				hasNonNull = true
+				allStringsOrNull = false
 				allTuples = false
 			} else {
-				allNumeric = false
-				allStrings = false
+				allNumericOrNull = false
+				allStringsOrNull = false
 				allTuples = false
 				break
 			}
 		}
 		// For tuples, only combine if all contain primitive literals
-		canBeTupleLiteral = allNumeric || allStrings || (allTuples && allTuplesArePrimitive)
+		canBeTupleLiteral = hasNonNull && (allNumericOrNull || allStringsOrNull || (allTuples && allTuplesArePrimitive))
 	}
 
 	// Count arguments: expr + list items or subquery
@@ -814,17 +821,23 @@ func explainInExprWithAlias(sb *strings.Builder, n *ast.InExpr, alias string, in
 	const maxStringTupleSizeWithAlias = 10
 	canBeTupleLiteral := false
 	if n.Query == nil && len(n.List) > 1 {
-		allNumeric := true
-		allStrings := true
+		allNumericOrNull := true
+		allStringsOrNull := true
 		allTuples := true
 		allTuplesArePrimitive := true
+		hasNonNull := false // Need at least one non-null value
 		for _, item := range n.List {
 			if lit, ok := item.(*ast.Literal); ok {
+				if lit.Type == ast.LiteralNull {
+					// NULL is compatible with both numeric and string lists
+					continue
+				}
+				hasNonNull = true
 				if lit.Type != ast.LiteralInteger && lit.Type != ast.LiteralFloat {
-					allNumeric = false
+					allNumericOrNull = false
 				}
 				if lit.Type != ast.LiteralString {
-					allStrings = false
+					allStringsOrNull = false
 				}
 				if lit.Type != ast.LiteralTuple {
 					allTuples = false
@@ -834,16 +847,17 @@ func explainInExprWithAlias(sb *strings.Builder, n *ast.InExpr, alias string, in
 					}
 				}
 			} else if isNumericExpr(item) {
-				allStrings = false
+				hasNonNull = true
+				allStringsOrNull = false
 				allTuples = false
 			} else {
-				allNumeric = false
-				allStrings = false
+				allNumericOrNull = false
+				allStringsOrNull = false
 				allTuples = false
 				break
 			}
 		}
-		canBeTupleLiteral = allNumeric || (allStrings && len(n.List) <= maxStringTupleSizeWithAlias) || (allTuples && allTuplesArePrimitive)
+		canBeTupleLiteral = hasNonNull && (allNumericOrNull || (allStringsOrNull && len(n.List) <= maxStringTupleSizeWithAlias) || (allTuples && allTuplesArePrimitive))
 	}
 
 	// Count arguments

parser/testdata/00441_nulls_in/metadata.json

@@ -1,13 +1,9 @@
 {
   "explain_todo": {
-    "stmt1": true,
     "stmt13": true,
     "stmt14": true,
     "stmt15": true,
     "stmt16": true,
-    "stmt17": true,
-    "stmt2": true,
-    "stmt7": true,
-    "stmt8": true
+    "stmt17": true
   }
 }

parser/testdata/00939_test_null_in/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt6": true
-  }
-}
+{}

parser/testdata/01231_operator_null_in/metadata.json

@@ -1,20 +1 @@
-{
-  "explain_todo": {
-    "stmt10": true,
-    "stmt12": true,
-    "stmt13": true,
-    "stmt15": true,
-    "stmt17": true,
-    "stmt19": true,
-    "stmt20": true,
-    "stmt22": true,
-    "stmt23": true,
-    "stmt25": true,
-    "stmt26": true,
-    "stmt28": true,
-    "stmt4": true,
-    "stmt6": true,
-    "stmt7": true,
-    "stmt9": true
-  }
-}
+{}

parser/testdata/01410_nullable_key_and_index/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt26": true
-  }
-}
+{}

parser/testdata/01507_transform_null_in/metadata.json

@@ -1,7 +1 @@
-{
-  "explain_todo": {
-    "stmt4": true,
-    "stmt6": true,
-    "stmt9": true
-  }
-}
+{}

parser/testdata/01558_transform_null_in/metadata.json

@@ -1,14 +1,5 @@
 {
   "explain_todo": {
-    "stmt15": true,
-    "stmt16": true,
-    "stmt17": true,
-    "stmt18": true,
-    "stmt19": true,
-    "stmt20": true,
-    "stmt21": true,
-    "stmt5": true,
-    "stmt6": true,
-    "stmt9": true
+    "stmt21": true
   }
 }

parser/testdata/01756_optimize_skip_unused_shards_rewrite_in/metadata.json

@@ -2,7 +2,6 @@
   "explain_todo": {
     "stmt45": true,
     "stmt46": true,
-    "stmt53": true,
     "stmt56": true,
     "stmt57": true
   }

parser/testdata/02499_analyzer_aggregate_function_lambda_crash_fix/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt2": true,
-    "stmt3": true
-  }
-}
+{}

parser/testdata/03234_evaluate_constant_analyzer/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt1": true
-  }
-}
+{}