fix(aws-redshift): Columns are not dropped on removal from array (aws…

…#23011)

When attempting to a drop a column from the array, this would cause an error similar to that of the following
```Received response status [FAILED] from custom resource. Message returned: Statement status was FAILED: ERROR: column "column" of relation "table” already exists```

fixes aws#22208

----

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packages/@aws-cdk/aws-redshift/lib/private/database-query-provider/table.ts

@@ -88,8 +88,11 @@ async function updateTable(
   }
 
   const oldTableColumns = oldResourceProperties.tableColumns;
-  if (!oldTableColumns.every(oldColumn => tableColumns.some(column => column.name === oldColumn.name && column.dataType === oldColumn.dataType))) {
-    return createTable(tableNamePrefix, tableNameSuffix, tableColumns, tableAndClusterProps);
+  const columnDeletions = oldTableColumns.filter(oldColumn => (
+    tableColumns.every(column => oldColumn.name !== column.name)
+  ));
+  if (columnDeletions.length > 0) {
+    alterationStatements.push(...columnDeletions.map(column => `ALTER TABLE ${tableName} DROP COLUMN ${column.name}`));
   }
 
   const columnAdditions = tableColumns.filter(column => {

packages/@aws-cdk/aws-redshift/lib/table.ts

@@ -55,7 +55,9 @@ export enum TableAction {
  */
 export interface Column {
   /**
-   * The name of the column.
+   * The unique name/identifier of the column.
+   *
+   * **NOTE**. After deploying this column, you cannot change its name. Doing so will cause the column to be dropped and recreated.
    */
   readonly name: string;
 

packages/@aws-cdk/aws-redshift/test/database-query-provider/table.test.ts

@@ -225,20 +225,17 @@ describe('update', () => {
     }));
   });
 
-  test('replaces if table columns change', async () => {
-    const newTableColumnName = 'col2';
-    const newTableColumnDataType = 'varchar(1)';
-    const newTableColumns = [{ name: newTableColumnName, dataType: newTableColumnDataType }];
+  test('does not replace if table columns removed', async () => {
     const newResourceProperties = {
       ...resourceProperties,
-      tableColumns: newTableColumns,
+      tableColumns: [],
     };
 
-    await expect(manageTable(newResourceProperties, event)).resolves.not.toMatchObject({
+    await expect(manageTable(newResourceProperties, event)).resolves.toMatchObject({
       PhysicalResourceId: physicalResourceId,
     });
     expect(mockExecuteStatement).toHaveBeenCalledWith(expect.objectContaining({
-      Sql: `CREATE TABLE ${tableNamePrefix}${requestIdTruncated} (${newTableColumnName} ${newTableColumnDataType})`,
+      Sql: `ALTER TABLE ${physicalResourceId} DROP COLUMN col1`,
     }));
   });