feat: support EXPLAIN for DML and simplify ExplainStatement

- parse EXPLAIN with SELECT/INSERT/UPDATE/DELETE/MERGE (including WITH)
- unify ExplainStatement target to Statement (remove Select-only API)
- add regression tests for EXPLAIN DELETE/UPDATE/INSERT

Author: dengliming

src/main/java/net/sf/jsqlparser/statement/ExplainStatement.java

@@ -13,16 +13,14 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.stream.Collectors;
-
 import net.sf.jsqlparser.schema.Table;
-import net.sf.jsqlparser.statement.select.Select;
 
 /**
  * An {@code EXPLAIN} statement
  */
 public class ExplainStatement implements Statement {
     private String keyword;
-    private Select select;
+    private Statement statement;
     private LinkedHashMap<OptionType, Option> options;
     private Table table;
 
@@ -37,24 +35,17 @@ public ExplainStatement() {
     public ExplainStatement(String keyword, Table table) {
         this.keyword = keyword;
         this.table = table;
-        this.select = null;
     }
 
-    public ExplainStatement(String keyword, Select select, List<Option> optionList) {
+    public ExplainStatement(String keyword, Statement statement, List<Option> optionList) {
         this.keyword = keyword;
-        this.select = select;
-        this.table = null;
+        setStatement(statement);
 
-        if (optionList != null && !optionList.isEmpty()) {
-            options = new LinkedHashMap<>();
-            for (Option o : optionList) {
-                options.put(o.getType(), o);
-            }
-        }
+        initializeOptions(optionList);
     }
 
-    public ExplainStatement(Select select) {
-        this("EXPLAIN", select, null);
+    public ExplainStatement(Statement statement) {
+        this("EXPLAIN", statement, null);
     }
 
     public Table getTable() {
@@ -63,15 +54,20 @@ public Table getTable() {
 
     public ExplainStatement setTable(Table table) {
         this.table = table;
+        if (table != null) {
+            this.statement = null;
+        }
         return this;
     }
 
-    public Select getStatement() {
-        return select;
+    public Statement getStatement() {
+        return statement;
     }
 
-    public void setStatement(Select select) {
-        this.select = select;
+    public ExplainStatement setStatement(Statement statement) {
+        this.table = null;
+        this.statement = statement;
+        return this;
     }
 
     public LinkedHashMap<OptionType, Option> getOptions() {
@@ -122,8 +118,8 @@ public String toString() {
             }
 
             builder.append(" ");
-            if (select != null) {
-                select.appendTo(builder);
+            if (statement != null) {
+                builder.append(statement);
             }
         }
 
@@ -135,6 +131,15 @@ public <T, S> T accept(StatementVisitor<T> statementVisitor, S context) {
         return statementVisitor.visit(this, context);
     }
 
+    private void initializeOptions(List<Option> optionList) {
+        if (optionList != null && !optionList.isEmpty()) {
+            options = new LinkedHashMap<>();
+            for (Option o : optionList) {
+                options.put(o.getType(), o);
+            }
+        }
+    }
+
     public enum OptionType {
         ANALYZE, VERBOSE, COSTS, BUFFERS, FORMAT, PLAN, PLAN_FOR;
 

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -2359,7 +2359,8 @@ DescribeStatement Describe(): {
 ExplainStatement Explain():
 {
     Token tk;
-    Select select;
+    Statement statement;
+    List<WithItem<?>> with = null;
     Table table;
     List<ExplainStatement.Option> options;
     ExplainStatement es;
@@ -2369,9 +2370,18 @@ ExplainStatement Explain():
     (
         LOOKAHEAD(3)(
             options= ExplainStatementOptions()
-            select = Select( )
+            (
+                [ LOOKAHEAD(2) with=WithList() ]
+                (
+                    statement = SelectWithWithItems( with )
+                    | statement = InsertWithWithItems( with )
+                    | statement = UpdateWithWithItems( with )
+                    | statement = DeleteWithWithItems( with )
+                    | statement = Merge( with )
+                )
+            )
             {
-                es = new ExplainStatement(tk.image, select, options);
+                es = new ExplainStatement(tk.image, statement, options);
             }
         )
         |

src/test/java/net/sf/jsqlparser/statement/ExplainTest.java

@@ -9,10 +9,12 @@
  */
 package net.sf.jsqlparser.statement;
 
-import net.sf.jsqlparser.JSQLParserException;
-import net.sf.jsqlparser.parser.CCJSqlParserUtil;
 import static net.sf.jsqlparser.test.TestUtils.*;
 import static org.assertj.core.api.Assertions.assertThat;
+
+import net.sf.jsqlparser.JSQLParserException;
+import net.sf.jsqlparser.parser.CCJSqlParserUtil;
+import net.sf.jsqlparser.statement.delete.Delete;
 import org.junit.jupiter.api.Test;
 
 public class ExplainTest {
@@ -72,4 +74,34 @@ public void getOption_returnsValues() throws JSQLParserException {
         explain = (ExplainStatement) CCJSqlParserUtil.parse("EXPLAIN SELECT * FROM mytable");
         assertThat(explain.getOption(ExplainStatement.OptionType.ANALYZE)).isNull();
     }
+
+    @Test
+    public void testDelete() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("EXPLAIN DELETE FROM mytable");
+    }
+
+    @Test
+    public void testUpdate() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("EXPLAIN UPDATE mytable SET col = 1");
+    }
+
+    @Test
+    public void testInsert() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("EXPLAIN INSERT INTO mytable (col) VALUES (1)");
+    }
+
+    @Test
+    public void explainDelete_usesGenericStatementSlot() throws JSQLParserException {
+        ExplainStatement explain =
+                (ExplainStatement) CCJSqlParserUtil.parse("EXPLAIN DELETE FROM mytable");
+        assertThat(explain.getStatement()).isInstanceOf(Delete.class);
+    }
+
+    @Test
+    public void testDeleteInStatementsList() throws JSQLParserException {
+        Statements statements = CCJSqlParserUtil.parseStatements("EXPLAIN DELETE FROM mytable;");
+        assertThat(statements).isNotNull();
+        assertThat(statements).hasSize(1);
+        assertThat(statements.get(0)).isInstanceOf(ExplainStatement.class);
+    }
 }