Add SETTINGS clause support for lightweight DELETE statements

Parse and output SETTINGS clause for DELETE FROM queries, matching
ClickHouse's EXPLAIN AST format.

Author: claude

ast/ast.go

@@ -709,6 +709,7 @@ type DeleteQuery struct {
 	Database string         `json:"database,omitempty"`
 	Table    string         `json:"table"`
 	Where    Expression     `json:"where,omitempty"`
+	Settings []*SettingExpr `json:"settings,omitempty"`
 }
 
 func (d *DeleteQuery) Pos() token.Position { return d.Position }

internal/explain/statements.go

@@ -2026,17 +2026,23 @@ func explainDeleteQuery(sb *strings.Builder, n *ast.DeleteQuery, indent string,
 		return
 	}
 
-	// Count children: Where expression + table identifier
+	// Count children: Where expression + table identifier + settings
 	children := 1 // table identifier
 	if n.Where != nil {
 		children++
 	}
+	if len(n.Settings) > 0 {
+		children++
+	}
 
 	fmt.Fprintf(sb, "%sDeleteQuery  %s (children %d)\n", indent, n.Table, children)
 	if n.Where != nil {
 		Node(sb, n.Where, depth+1)
 	}
 	fmt.Fprintf(sb, "%s Identifier %s\n", indent, n.Table)
+	if len(n.Settings) > 0 {
+		fmt.Fprintf(sb, "%s Set\n", indent)
+	}
 }
 
 func explainCheckQuery(sb *strings.Builder, n *ast.CheckQuery, indent string) {

parser/parser.go

@@ -6002,6 +6002,12 @@ func (p *Parser) parseDelete() *ast.DeleteQuery {
 		del.Where = p.parseExpression(LOWEST)
 	}
 
+	// Parse SETTINGS clause
+	if p.currentIs(token.SETTINGS) {
+		p.nextToken() // skip SETTINGS
+		del.Settings = p.parseSettingsList()
+	}
+
 	return del
 }
 

parser/testdata/02428_delete_with_settings/metadata.json

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

parser/testdata/02581_share_big_sets_between_multiple_mutations_tasks_long/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt16": true
-  }
-}
+{}

parser/testdata/03033_lightweight_deletes_sync/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt4": true,
-    "stmt8": true
-  }
-}
+{}

parser/testdata/03100_lwu_46_deletes_skip_indexes/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt6": true,
-    "stmt7": true
-  }
-}
+{}

parser/testdata/03173_forbid_qualify/metadata.json

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

parser/testdata/03256_invalid_mutation_query/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt9": true
-  }
-}
+{}

parser/testdata/03442_lightweight_deletes_on_fly/metadata.json

@@ -1,7 +1 @@
-{
-  "explain_todo": {
-    "stmt13": true,
-    "stmt16": true,
-    "stmt8": true
-  }
-}
+{}