improved sql parser for mysql explain. for issue #1645

src/main/java/com/alibaba/druid/sql/ast/statement/SQLExplainStatement.java

@@ -24,6 +24,8 @@ import com.alibaba.druid.sql.visitor.SQLASTVisitor;
 
 public class SQLExplainStatement extends SQLStatementImpl {
 
+    private String type;
+
     protected SQLStatement       statement;
 
     private List<SQLCommentHint> hints;
@@ -47,6 +49,14 @@ public class SQLExplainStatement extends SQLStatementImpl {
         this.statement = statement;
     }
 
+    public String getType() {
+        return type;
+    }
+
+    public void setType(String type) {
+        this.type = type;
+    }
+
     @Override
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {

src/main/java/com/alibaba/druid/sql/parser/SQLStatementParser.java

@@ -2087,6 +2087,15 @@ public class SQLStatementParser extends SQLParser {
             explain.setHints(this.exprParser.parseHints());
         }
 
+        if (JdbcConstants.MYSQL.equals(dbType)) {
+            if (identifierEquals("FORMAT")
+                    || identifierEquals("EXTENDED")
+                    || identifierEquals("PARTITIONS")) {
+                explain.setType(lexer.stringVal);
+                lexer.nextToken();
+            }
+        }
+
         explain.setStatement(parseStatement());
 
         return explain;

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -2631,6 +2631,11 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Paramet
             print(' ');
             printAndAccept(x.getHints(), " ");
         }
+
+        if (x.getType() != null) {
+            print(' ');
+            print0(x.getType());
+        }
         println();
         x.getStatement().accept(this);
         return false;