supporting PG syntax 'ALTER COLUMN ... SET DATA TYPE ...'

core/src/main/java/com/alibaba/druid/sql/ast/statement/SQLAlterTableAlterColumn.java

@@ -33,12 +33,14 @@ public class SQLAlterTableAlterColumn extends SQLObjectImpl implements SQLAlterT
     private SQLName after;
     private SQLDataType dataType;
     private boolean toFirst;
+    private SQLExpr using;
 
     @Override
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {
             acceptChild(visitor, column);
             acceptChild(visitor, setDefault);
+            acceptChild(visitor, using);
         }
         visitor.endVisit(this);
     }
@@ -124,4 +126,16 @@ public void setDataType(SQLDataType x) {
         }
         this.dataType = x;
     }
+
+    public SQLExpr getUsing() {
+        return using;
+    }
+
+    public void setUsing(SQLExpr using) {
+        if (using != null) {
+            using.setParent(this);
+        }
+        this.using = using;
+    }
+
 }

core/src/main/java/com/alibaba/druid/sql/dialect/postgresql/parser/PGSQLStatementParser.java

@@ -787,6 +787,18 @@ protected SQLAlterTableAlterColumn parseAlterColumn() {
                     lexer.nextToken();
                     accept(Token.NULL);
                     alterColumn.setSetNotNull(true);
+                } else if (lexer.identifierEquals("DATA")) {
+                    // alter column ... set data type ...
+                    lexer.nextToken();
+                    accept(Token.TYPE);
+                    SQLDataType dataType = this.exprParser.parseDataType();
+                    alterColumn.setDataType(dataType);
+                    // using ...
+                    if (lexer.token() == USING) {
+                        lexer.nextToken();
+                        SQLExpr usingExpr = this.exprParser.expr();
+                        alterColumn.setUsing(usingExpr);
+                    }
                 } else {
                     accept(Token.DEFAULT);
                     SQLExpr defaultValue = this.exprParser.expr();

core/src/main/java/com/alibaba/druid/sql/dialect/postgresql/visitor/PGOutputVisitor.java

@@ -2995,6 +2995,15 @@ public boolean visit(SQLIntervalExpr x) {
         return false;
     }
 
+    public boolean visit(SQLAlterTableAlterColumn x) {
+        super.visit(x);
+        if (x.getUsing() != null) {
+            print0(ucase ? " USING " : " using ");
+            x.getUsing().accept(this);
+        }
+        return false;
+    }
+
     @Override
     protected void printTableOptionsPrefix(SQLCreateTableStatement x) {
         println();

core/src/test/java/com/alibaba/druid/sql/dialect/postgresql/parser/PGSQLStatementParserTest.java

@@ -0,0 +1,257 @@
+package com.alibaba.druid.sql.dialect.postgresql.parser;
+
+import com.alibaba.druid.DbType;
+import com.alibaba.druid.sql.SQLUtils;
+import com.alibaba.druid.sql.ast.SQLStatement;
+import com.alibaba.druid.sql.ast.expr.SQLCastExpr;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableAlterColumn;
+import com.alibaba.druid.sql.ast.statement.SQLAlterTableStatement;
+import com.alibaba.druid.sql.dialect.postgresql.visitor.PGSchemaStatVisitor;
+import com.alibaba.druid.sql.parser.ParserException;
+import com.alibaba.druid.stat.TableStat;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * @author gaattc
+ * @since 1.2.24
+ */
+public class PGSQLStatementParserTest {
+
+    /**
+     * ALTER COLUMN ... SET DATA TYPE ...
+     */
+    @Test
+    public void testAlterColumnSetDataType() {
+        String sql = "alter table if exists products alter column price set data type decimal(12,2)";
+
+        PGSQLStatementParser parser = new PGSQLStatementParser(sql);
+        List<SQLStatement> statementList = parser.parseStatementList();
+
+        assertEquals(1, statementList.size());
+        SQLAlterTableStatement stmt = (SQLAlterTableStatement) statementList.get(0);
+        assertEquals(SQLAlterTableStatement.class, stmt.getClass());
+
+        assertEquals("products", stmt.getTableName());
+        assertTrue(stmt.isIfExists());
+
+        SQLAlterTableAlterColumn alterColumnItem = (SQLAlterTableAlterColumn) stmt.getItems().get(0);
+        assertNotNull(alterColumnItem);
+
+        assertEquals("price", alterColumnItem.getColumn().getName().getSimpleName());
+        assertNotNull(alterColumnItem.getDataType());
+        assertEquals("decimal", alterColumnItem.getDataType().getName().toLowerCase());
+        assertEquals(2, alterColumnItem.getDataType().getArguments().size());
+        assertEquals("12", alterColumnItem.getDataType().getArguments().get(0).toString());
+        assertEquals("2", alterColumnItem.getDataType().getArguments().get(1).toString());
+
+        String outputSql = stmt.toString();
+        assertEquals("ALTER TABLE IF EXISTS products\n\tALTER COLUMN price SET DATA TYPE decimal(12, 2)", outputSql);
+    }
+
+    /**
+     * ALTER COLUMN ... SET DEFAULT ...
+     */
+    @Test
+    public void testAlterColumnSetDefault() {
+        String sql = "ALTER TABLE products ALTER COLUMN price SET DEFAULT 7.77";
+
+        PGSQLStatementParser parser = new PGSQLStatementParser(sql);
+        List<SQLStatement> statementList = parser.parseStatementList();
+        SQLAlterTableStatement stmt = (SQLAlterTableStatement) statementList.get(0);
+
+        SQLAlterTableAlterColumn alterColumnItem = (SQLAlterTableAlterColumn) stmt.getItems().get(0);
+
+        assertEquals("price", alterColumnItem.getColumn().getName().getSimpleName());
+        assertNotNull(alterColumnItem.getSetDefault());
+        assertEquals("7.77", alterColumnItem.getSetDefault().toString());
+        assertNull(alterColumnItem.getDataType());
+    }
+
+    /**
+     * ALTER COLUMN ... SET NOT NULL
+     */
+    @Test
+    public void testAlterColumnSetNotNull() {
+        String sql = "ALTER TABLE products ALTER COLUMN price SET NOT NULL";
+
+        PGSQLStatementParser parser = new PGSQLStatementParser(sql);
+        List<SQLStatement> statementList = parser.parseStatementList();
+        SQLAlterTableStatement stmt = (SQLAlterTableStatement) statementList.get(0);
+
+        SQLAlterTableAlterColumn alterColumnItem = (SQLAlterTableAlterColumn) stmt.getItems().get(0);
+
+        assertEquals("price", alterColumnItem.getColumn().getName().getSimpleName());
+        assertTrue(alterColumnItem.isSetNotNull());
+        assertNull(alterColumnItem.getDataType());
+    }
+
+    /**
+     * DROP
+     */
+    @Test
+    public void testAlterColumnDropDefault() {
+        String sql = "ALTER TABLE products ALTER COLUMN price DROP DEFAULT";
+
+        PGSQLStatementParser parser = new PGSQLStatementParser(sql);
+        List<SQLStatement> statementList = parser.parseStatementList();
+        SQLAlterTableStatement stmt = (SQLAlterTableStatement) statementList.get(0);
+
+        SQLAlterTableAlterColumn alterColumnItem = (SQLAlterTableAlterColumn) stmt.getItems().get(0);
+
+        assertEquals("price", alterColumnItem.getColumn().getName().getSimpleName());
+        assertTrue(alterColumnItem.isDropDefault());
+        assertNull(alterColumnItem.getDataType());
+    }
+
+    /**
+     * 测试核心功能：ALTER COLUMN ... SET DATA TYPE ... USING ...
+     */
+    @Test
+    public void testAlterColumnSetDataTypeWithUsing() {
+        String sql = "ALTER TABLE my_table ALTER COLUMN my_column SET DATA TYPE integer USING my_column::integer";
+
+        SQLAlterTableStatement stmt = parseSingleAlterStatement(sql);
+
+        // 验证表名
+        assertEquals("my_table", stmt.getTableName());
+
+        SQLAlterTableAlterColumn item = (SQLAlterTableAlterColumn) stmt.getItems().get(0);
+
+        // 验证列名
+        assertEquals("my_column", item.getColumn().getName().getSimpleName());
+
+        // 验证新数据类型
+        assertEquals("integer", item.getDataType().getName().toLowerCase());
+
+        // 验证 USING 子句
+        assertNotNull("USING clause should be parsed", item.getUsing());
+        assertTrue("USING expression should be a CAST expression", item.getUsing() instanceof SQLCastExpr);
+        assertEquals("my_column::integer", SQLUtils.toPGString(item.getUsing()));
+    }
+
+    /**
+     * 边界场景测试：测试带有 schema 的复杂类型名
+     */
+    @Test
+    public void testAlterColumnWithSchemaQualifiedType() {
+        String sql = "ALTER TABLE public.users ALTER COLUMN user_status SET DATA TYPE custom_schema.user_enum USING user_status::text::custom_schema.user_enum";
+
+        SQLAlterTableStatement stmt = parseSingleAlterStatement(sql);
+
+        // 验证带 schema 的表名
+        assertEquals("public.users", stmt.getTableSource().toString());
+
+        SQLAlterTableAlterColumn item = (SQLAlterTableAlterColumn) stmt.getItems().get(0);
+
+        // 验证数据类型
+        assertEquals("custom_schema.user_enum", item.getDataType().toString());
+
+        // 验证 USING 子句
+        assertNotNull(item.getUsing());
+        assertEquals("custom_schema.user_enum(user_status::text)", SQLUtils.toPGString(item.getUsing()));
+    }
+
+    /**
+     * 测试 Visitor 还原 PG 语法的完整性
+     * 确保解析后的AST能够被 Visitor 正确地还原为原始 SQL 或等价的 PG SQL。
+     */
+    @Test
+    public void testVisitorOutputCompleteness() {
+        String originalSql = "ALTER TABLE my_table ALTER COLUMN my_column SET DATA TYPE integer USING my_column::integer";
+        SQLStatement stmt = parseSingleAlterStatement(originalSql);
+
+        // 使用 SQLUtils (其内部使用 Visitor) 来格式化 SQL
+        String formattedSql = SQLUtils.toSQLString(stmt, DbType.postgresql, new SQLUtils.FormatOption(true, true));
+
+        String expectedFormattedSql =
+                "ALTER TABLE my_table\n" +
+                        "\tALTER COLUMN my_column SET DATA TYPE integer USING my_column::integer";
+
+        assertEquals(expectedFormattedSql, formattedSql);
+    }
+
+    /**
+     * 测试 Visitor 统计功能的正确性
+     */
+    @Test
+    public void testSchemaStatVisitorWithUsing() {
+        String sql = "ALTER TABLE my_table ALTER COLUMN my_column SET DATA TYPE integer USING old_column::integer";
+
+        // 使用 SQLUtils.parseStatements 来简化解析
+        SQLStatement stmt = SQLUtils.parseStatements(sql, DbType.postgresql).get(0);
+
+        PGSchemaStatVisitor visitor = new PGSchemaStatVisitor();
+        stmt.accept(visitor);
+
+        // 验证表被识别
+        assertTrue("The table 'my_table' should be present in the stats.",
+                visitor.containsTable("my_table"));
+
+        // 验证 ALTER COLUMN <column> 被识别
+        TableStat.Column myColumnStat = visitor.getColumn("my_table", "my_column");
+        assertNotNull("The altered column 'my_column' should be identified by the visitor.", myColumnStat);
+
+        // 验证 USING <column> 被识别
+        TableStat.Column oldColumnStat = visitor.getColumn("my_table", "old_column");
+        assertNotNull("The column 'old_column' from the USING clause should be identified by the visitor.", oldColumnStat);
+    }
+
+    /**
+     * 异常场景测试：测试非法的 'SET DATA' 语法
+     */
+    @Test(expected = ParserException.class)
+    public void testInvalidSyntax_SetDataWithoutType() {
+        String sql = "ALTER TABLE my_table ALTER COLUMN my_column SET DATA my_column";
+        // 应该在解析 'my_column' 时报错，因为它期望 'TYPE'
+        parseSingleAlterStatement(sql);
+    }
+
+    /**
+     * 异常场景测试：测试 'SET DATA TYPE' 后缺少类型定义
+     */
+    @Test(expected = ParserException.class)
+    public void testInvalidSyntax_SetDataTypeWithoutDefinition() {
+        String sql = "ALTER TABLE my_table ALTER COLUMN my_column SET DATA TYPE";
+        // 解析到末尾，发现缺少数据类型，应该报错
+        parseSingleAlterStatement(sql);
+    }
+
+    /**
+     * 异常场景测试：测试 'USING' 关键字后缺少表达式
+     */
+    @Test(expected = ParserException.class)
+    public void testInvalidSyntax_UsingWithoutExpression() {
+        String sql = "ALTER TABLE my_table ALTER COLUMN my_column SET DATA TYPE integer USING";
+        // 解析到末尾，发现缺少 USING 表达式，应该报错
+        parseSingleAlterStatement(sql);
+    }
+
+    /**
+     * 辅助方法，用于解析单条 ALTER 语句并返回其 AST
+     * @param sql SQL 字符串
+     * @return SQLAlterTableStatement 对象
+     */
+    private SQLAlterTableStatement parseSingleAlterStatement(String sql) {
+        PGSQLStatementParser parser = new PGSQLStatementParser(sql);
+        List<SQLStatement> statementList = parser.parseStatementList();
+
+        if (statementList.size() != 1) {
+            Assert.fail("Expected a single statement, but got " + statementList.size());
+        }
+
+        SQLStatement stmt = statementList.get(0);
+        if (!(stmt instanceof SQLAlterTableStatement)) {
+            Assert.fail("Expected SQLAlterTableStatement, but got " + stmt.getClass().getName());
+        }
+        return (SQLAlterTableStatement) stmt;
+    }
+
+}