Fix projection indentation in EXPLAIN output

- Remove extra space before "Projection" in explainProjection format string
- Adjust indent passed to explainProjectionSelectQuery from +2 to +1 spaces
- Add space to indent when calling explainProjection from AlterCommand

This fixes indentation for projections in both CREATE TABLE and ALTER TABLE
ADD PROJECTION statements to match ClickHouse's EXPLAIN AST output.

Author: claude

internal/explain/statements.go

@@ -925,7 +925,7 @@ func explainAlterCommand(sb *strings.Builder, cmd *ast.AlterCommand, indent stri
 		}
 	case ast.AlterAddProjection:
 		if cmd.Projection != nil {
-			explainProjection(sb, cmd.Projection, indent, depth+1)
+			explainProjection(sb, cmd.Projection, indent+" ", depth+1)
 		}
 	case ast.AlterDropProjection, ast.AlterMaterializeProjection, ast.AlterClearProjection:
 		if cmd.ProjectionName != "" {
@@ -947,9 +947,9 @@ func explainProjection(sb *strings.Builder, p *ast.Projection, indent string, de
 	if p.Select != nil {
 		children++
 	}
-	fmt.Fprintf(sb, "%s Projection (children %d)\n", indent, children)
+	fmt.Fprintf(sb, "%sProjection (children %d)\n", indent, children)
 	if p.Select != nil {
-		explainProjectionSelectQuery(sb, p.Select, indent+"  ", depth+1)
+		explainProjectionSelectQuery(sb, p.Select, indent+" ", depth+1)
 	}
 }
 

parser/testdata/01576_alias_column_rewrite/metadata.json

@@ -1,7 +1,6 @@
 {
   "explain_todo": {
     "stmt23": true,
-    "stmt42": true,
-    "stmt51": true
+    "stmt42": true
   }
 }

parser/testdata/01701_clear_projection_and_part_remove/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt2": true,
     "stmt7": true,
     "stmt8": true
   }

parser/testdata/01705_normalize_create_alter_function_names/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt2": true,
     "stmt3": true
   }
 }

parser/testdata/01710_aggregate_projection_with_grouping_set/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt2": true,
     "stmt4": true
   }
 }

parser/testdata/01710_aggregate_projection_with_monotonic_key_expr/metadata.json

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

parser/testdata/01710_aggregate_projection_with_normalized_states/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt2": true,
-    "stmt3": true
+    "stmt2": true
   }
 }

parser/testdata/01710_force_use_projection/metadata.json

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

parser/testdata/01710_normal_projection_with_query_plan_optimization/metadata.json

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

parser/testdata/01710_order_by_projections_complete/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt2": true,
     "stmt3": true
   }
 }