Always show SAMPLE BY in CREATE TABLE EXPLAIN output

Previously, SAMPLE BY was only shown when it was a function (not an
identifier) and when different from ORDER BY. ClickHouse's actual
EXPLAIN AST output always shows SAMPLE BY when present.

This fixes 27 statements across 19 tests including:
- 02559_add_parts
- 00578_merge_table_sampling
- 02380_analyzer_join_sample
- 03227_test_sample_n
- And 15 more SAMPLE BY related tests

Author: claude

internal/explain/statements.go

@@ -282,24 +282,9 @@ func explainCreateQuery(sb *strings.Builder, n *ast.CreateQuery, indent string,
 		if len(n.PrimaryKey) > 0 {
 			storageChildren++
 		}
-		// SAMPLE BY is only shown in EXPLAIN AST when it's a function (not a simple identifier)
-		// and when it's different from ORDER BY
+		// SAMPLE BY is always shown in EXPLAIN AST when present
 		if n.SampleBy != nil {
-			if _, isIdent := n.SampleBy.(*ast.Identifier); !isIdent {
-				// Check if SAMPLE BY equals ORDER BY - if so, don't show it
-				showSampleBy := true
-				if len(n.OrderBy) == 1 {
-					var orderBySb, sampleBySb strings.Builder
-					Node(&orderBySb, n.OrderBy[0], 0)
-					Node(&sampleBySb, n.SampleBy, 0)
-					if orderBySb.String() == sampleBySb.String() {
-						showSampleBy = false
-					}
-				}
-				if showSampleBy {
-					storageChildren++
-				}
-			}
+			storageChildren++
 		}
 		if n.TTL != nil {
 			storageChildren++
@@ -395,24 +380,9 @@ func explainCreateQuery(sb *strings.Builder, n *ast.CreateQuery, indent string,
 				}
 			}
 		}
-		// SAMPLE BY is only shown in EXPLAIN AST when it's a function (not a simple identifier)
-		// and when it's different from ORDER BY
+		// SAMPLE BY is always shown in EXPLAIN AST when present
 		if n.SampleBy != nil {
-			if _, isIdent := n.SampleBy.(*ast.Identifier); !isIdent {
-				// Check if SAMPLE BY equals ORDER BY - if so, don't show it
-				showSampleBy := true
-				if len(n.OrderBy) == 1 {
-					var orderBySb, sampleBySb strings.Builder
-					Node(&orderBySb, n.OrderBy[0], 0)
-					Node(&sampleBySb, n.SampleBy, 0)
-					if orderBySb.String() == sampleBySb.String() {
-						showSampleBy = false
-					}
-				}
-				if showSampleBy {
-					Node(sb, n.SampleBy, storageChildDepth)
-				}
-			}
+			Node(sb, n.SampleBy, storageChildDepth)
 		}
 		if n.TTL != nil {
 			fmt.Fprintf(sb, "%s ExpressionList (children 1)\n", storageIndent)

parser/testdata/00509_extended_storage_definition_syntax_zookeeper/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt22": true,
-    "stmt4": true
+    "stmt22": true
   }
 }

parser/testdata/00578_merge_table_sampling/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt8": true,
-    "stmt9": true
-  }
-}
+{}

parser/testdata/00712_prewhere_with_sampling/metadata.json

@@ -1 +1 @@
-{"explain_todo":{"stmt2":true,"stmt7":true}}
+{}

parser/testdata/00753_system_columns_and_system_tables_long/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true,
-    "stmt74": true
-  }
-}
+{}

parser/testdata/00983_summing_merge_tree_not_an_identifier/metadata.json

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

parser/testdata/01034_prewhere_max_parallel_replicas_distributed/metadata.json

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

parser/testdata/01557_max_parallel_replicas_no_sample/metadata.json

@@ -1 +1 @@
-{"explain_todo":{"stmt11":true}}
+{}

parser/testdata/01942_create_table_with_sample/metadata.json

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

parser/testdata/02002_sampling_and_unknown_column_bug/metadata.json

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