support DROP COLUMN IF EXISTS

zendesk · Sep 1, 2023 · 8d7ca38 · 8d7ca38
1 parent 4c1823e
commit 8d7ca38
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Showing 5 changed files with 29 additions and 5 deletions.
diff --git a/src/main/antlr4/imports/mysql_alter_table.g4 b/src/main/antlr4/imports/mysql_alter_table.g4
@@ -28,7 +28,8 @@ alter_specification:
 add_column: ADD COLUMN? if_not_exists? column_definition col_position?;
 add_column_parens: ADD COLUMN? if_not_exists? '(' (column_definition|index_definition) (',' (column_definition|index_definition))* ')';
 change_column: CHANGE COLUMN? full_column_name column_definition col_position?;
-drop_column: DROP COLUMN? full_column_name CASCADE?;
+if_exists: IF EXISTS;
+drop_column: DROP COLUMN? if_exists? full_column_name CASCADE?;
 modify_column: MODIFY COLUMN? column_definition col_position?;
 drop_key: DROP FOREIGN? (INDEX|KEY) name;
 drop_primary_key: DROP PRIMARY KEY;

diff --git a/src/main/java/com/zendesk/maxwell/schema/ddl/MysqlParserListener.java b/src/main/java/com/zendesk/maxwell/schema/ddl/MysqlParserListener.java
@@ -199,7 +199,7 @@ public void exitRename_column(Rename_columnContext ctx) {
 	@Override
 	public void exitDrop_column(mysqlParser.Drop_columnContext ctx) {
 		String colName = ctx.full_column_name().col_name.getText();
-		alterStatement().columnMods.add(new RemoveColumnMod(unquote(colName)));
+		alterStatement().columnMods.add(new RemoveColumnMod(unquote(colName), ctx.if_exists() != null));
 	}
 	@Override
 	public void exitCol_position(mysqlParser.Col_positionContext ctx) {

diff --git a/src/main/java/com/zendesk/maxwell/schema/ddl/RemoveColumnMod.java b/src/main/java/com/zendesk/maxwell/schema/ddl/RemoveColumnMod.java
@@ -5,12 +5,23 @@
 import java.util.List;
 
 class RemoveColumnMod extends ColumnMod {
-	public RemoveColumnMod(String name) {
+	private final boolean ifExists;
+	public RemoveColumnMod(String name, boolean ifExists) {
 		super(name);
+		this.ifExists = ifExists;
 	}
 
 	@Override
 	public void apply(Table table, List<DeferredPositionUpdate> deferred) throws InvalidSchemaError {
-		table.removeColumn(originalIndex(table));
+		int originalIndex = table.findColumnIndex(name);
+
+		if ( originalIndex == -1 ) {
+			if ( ifExists )
+				return;
+			else
+				throw new InvalidSchemaError("Could not find column " + name + " in " + table.getName());
+		}
+
+		table.removeColumn(originalIndex);
 	}
 }
diff --git a/src/test/java/com/zendesk/maxwell/schema/ddl/DDLIntegrationTest.java b/src/test/java/com/zendesk/maxwell/schema/ddl/DDLIntegrationTest.java
@@ -184,6 +184,17 @@ public void testModifyAndMoveColumn() throws Exception {
 
 	}
 
+	@Test
+	public void testDropColumnIfExists() throws Exception {
+		String sql[] = {
+			"CREATE TABLE t ( a varchar(255), b int)",
+			"ALTER TABLE t drop column if exists aa",
+			"ALTER TABLE t drop column if exists b, drop column if exists nothere"
+		};
+		testIntegration(sql);
+
+	}
+
 	@Test
 	public void testAddQualifiedColumn() throws Exception {
 		MaxwellTestSupport.assertMaximumVersion(server, new MysqlVersion(8, 0));

diff --git a/src/test/java/com/zendesk/maxwell/schema/ddl/DDLParserTest.java b/src/test/java/com/zendesk/maxwell/schema/ddl/DDLParserTest.java
@@ -266,7 +266,8 @@ public void testParsingSomeAlters() {
 			"ALTER TABLE tournaments ADD INDEX idx_team_name (('$.teams.name'))",
 			"ALTER TABLE tournaments ADD INDEX idx_team_name ((ABS(col)))",
 			"ALTER TABLE tournaments ADD INDEX idx_team_name ((col1 * 40) DESC)",
-			"CREATE TABLE employees (data JSON, INDEX idx ((CAST(data->>'$.name' AS CHAR(30)) COLLATE utf8mb4_bin)))"
+			"CREATE TABLE employees (data JSON, INDEX idx ((CAST(data->>'$.name' AS CHAR(30)) COLLATE utf8mb4_bin)))",
+			"ALTER TABLE tasks DROP COLUMN IF EXISTS snoozed_until"
 		};
 
 		for ( String s : testSQL ) {