Add CODEC/compression expression support in EXPLAIN output

Add codec rendering to the Column() function in the explain module.
CODEC expressions are now properly output as Function nodes with
ExpressionList children containing the individual codec functions.

This enables EXPLAIN AST output for column declarations with CODEC
specifications like CODEC(LZ4), CODEC(ZSTD(10)), CODEC(GCD, LZ4), etc.

Updates 62 metadata.json files to remove explain_todo entries for tests
that now pass.

Author: claude

internal/explain/explain.go

@@ -197,6 +197,9 @@ func Column(sb *strings.Builder, col *ast.ColumnDeclaration, depth int) {
 	if col.Default != nil || hasEphemeralDefault {
 		children++
 	}
+	if col.Codec != nil {
+		children++
+	}
 	fmt.Fprintf(sb, "%sColumnDeclaration %s (children %d)\n", indent, col.Name, children)
 	if col.Type != nil {
 		Node(sb, col.Type, depth+1)
@@ -207,6 +210,34 @@ func Column(sb *strings.Builder, col *ast.ColumnDeclaration, depth int) {
 		// EPHEMERAL columns without explicit default value show defaultValueOfTypeName function
 		fmt.Fprintf(sb, "%s Function defaultValueOfTypeName\n", indent)
 	}
+	if col.Codec != nil {
+		explainCodecExpr(sb, col.Codec, indent+" ", depth+1)
+	}
+}
+
+// explainCodecExpr handles CODEC expressions in column declarations
+func explainCodecExpr(sb *strings.Builder, codec *ast.CodecExpr, indent string, depth int) {
+	// CODEC is rendered as a Function with one child (ExpressionList of codecs)
+	fmt.Fprintf(sb, "%sFunction CODEC (children 1)\n", indent)
+	fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, len(codec.Codecs))
+	for _, c := range codec.Codecs {
+		explainCodecFunction(sb, c, indent+"  ", depth+2)
+	}
+}
+
+// explainCodecFunction handles individual codec functions (e.g., LZ4, ZSTD(10), Gorilla(1))
+func explainCodecFunction(sb *strings.Builder, fn *ast.FunctionCall, indent string, depth int) {
+	if len(fn.Arguments) == 0 {
+		// Codec without parameters: just the function name
+		fmt.Fprintf(sb, "%sFunction %s\n", indent, fn.Name)
+	} else {
+		// Codec with parameters: function with ExpressionList of arguments
+		fmt.Fprintf(sb, "%sFunction %s (children 1)\n", indent, fn.Name)
+		fmt.Fprintf(sb, "%s ExpressionList (children %d)\n", indent, len(fn.Arguments))
+		for _, arg := range fn.Arguments {
+			Node(sb, arg, depth+2)
+		}
+	}
 }
 
 func Index(sb *strings.Builder, idx *ast.IndexDefinition, depth int) {

parser/testdata/00162_mmap_compression_none/metadata.json

@@ -1 +1 @@
-{"explain_todo":{"stmt2":true}}
+{}

parser/testdata/00804_test_alter_compression_codecs/metadata.json

@@ -5,14 +5,8 @@
     "stmt20": true,
     "stmt21": true,
     "stmt27": true,
-    "stmt3": true,
-    "stmt30": true,
-    "stmt31": true,
-    "stmt32": true,
-    "stmt36": true,
     "stmt41": true,
     "stmt43": true,
-    "stmt7": true,
     "stmt8": true
   }
 }

parser/testdata/00804_test_custom_compression_codecs/metadata.json

@@ -1,17 +1 @@
-{
-  "explain_todo": {
-    "stmt22": true,
-    "stmt23": true,
-    "stmt24": true,
-    "stmt25": true,
-    "stmt26": true,
-    "stmt27": true,
-    "stmt28": true,
-    "stmt38": true,
-    "stmt4": true,
-    "stmt49": true,
-    "stmt50": true,
-    "stmt58": true,
-    "stmt69": true
-  }
-}
+{}

parser/testdata/00804_test_custom_compression_codes_log_storages/metadata.json

@@ -1,8 +1 @@
-{
-  "explain_todo": {
-    "stmt16": true,
-    "stmt28": true,
-    "stmt4": true,
-    "stmt40": true
-  }
-}
+{}

parser/testdata/00804_test_deflate_qpl_codec_compression/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt4": true
-  }
-}
+{}

parser/testdata/00804_test_delta_codec_compression/metadata.json

@@ -1,14 +1,8 @@
 {
   "explain_todo": {
     "stmt12": true,
-    "stmt18": true,
-    "stmt19": true,
     "stmt20": true,
     "stmt24": true,
-    "stmt30": true,
-    "stmt31": true,
-    "stmt36": true,
-    "stmt5": true,
-    "stmt6": true
+    "stmt36": true
   }
 }

parser/testdata/00804_test_delta_codec_no_type_alter/metadata.json

@@ -1 +1,8 @@
-{"explain_todo":{"stmt4":true,"stmt5":true,"stmt6":true,"stmt7":true,"stmt8":true,"stmt9":true}}
+{
+  "explain_todo": {
+    "stmt5": true,
+    "stmt6": true,
+    "stmt7": true,
+    "stmt9": true
+  }
+}

parser/testdata/00804_test_zstd_qat_codec_compression/metadata.json

@@ -1,7 +1 @@
-{
-  "explain_todo": {
-    "stmt4": true,
-    "stmt5": true,
-    "stmt6": true
-  }
-}
+{}

parser/testdata/00870_t64_codec/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt2": true
-  }
-}
+{}