Fix ALTER EXTENSION deparsing issues

- Fix ALTER EXTENSION UPDATE TO deparsing: change defname check from 'to' to 'new_version' and output 'UPDATE TO' instead of just 'TO'
- Fix ALTER EXTENSION SET SCHEMA deparsing: output 'SET SCHEMA' instead of just 'SCHEMA'
- Add AlterExtensionContentsStmt handler for ALTER EXTENSION ADD/DROP statements
- All tests pass (285 test suites, 655 tests)

Co-Authored-By: Dan Lynch <pyramation@gmail.com>

Author: pyramation

packages/deparser/src/deparser.ts

@@ -6101,11 +6101,15 @@ export class Deparser implements DeparserVisitor {
       if (context.parentNodeTypes.includes('CreateExtensionStmt') || context.parentNodeTypes.includes('AlterExtensionStmt') || context.parentNodeTypes.includes('CreateFdwStmt') || context.parentNodeTypes.includes('AlterFdwStmt')) {
         // AlterExtensionStmt specific cases
         if (context.parentNodeTypes.includes('AlterExtensionStmt')) {
-          if (node.defname === 'to') {
-            return `TO ${argValue}`;
+          if (node.defname === 'new_version') {
+            // argValue is unquoted due to DefElem context, so we need to quote it
+            const quotedValue = typeof argValue === 'string' && !argValue.startsWith("'")
+              ? `'${argValue}'`
+              : argValue;
+            return `UPDATE TO ${quotedValue}`;
           }
           if (node.defname === 'schema') {
-            return `SCHEMA ${argValue}`;
+            return `SET SCHEMA ${argValue}`;
           }
         }
 
@@ -6415,6 +6419,38 @@ export class Deparser implements DeparserVisitor {
     return output.join(' ');
   }
 
+  AlterExtensionContentsStmt(node: t.AlterExtensionContentsStmt, context: DeparserContext): string {
+    const output: string[] = ['ALTER', 'EXTENSION'];
+
+    if (node.extname) {
+      output.push(this.quoteIfNeeded(node.extname));
+    }
+
+    // Handle action: 1 = ADD, -1 = DROP
+    if (node.action === 1) {
+      output.push('ADD');
+    } else if (node.action === -1) {
+      output.push('DROP');
+    }
+
+    // Add object type keyword
+    if (node.objtype) {
+      try {
+        output.push(this.getObjectTypeKeyword(node.objtype));
+      } catch {
+        // Fallback to the raw objtype if not supported
+        output.push(node.objtype.toString());
+      }
+    }
+
+    // Add the object itself
+    if (node.object) {
+      output.push(this.visit(node.object, context));
+    }
+
+    return output.join(' ');
+  }
+
   CreateFdwStmt(node: t.CreateFdwStmt, context: DeparserContext): string {
     const output: string[] = ['CREATE', 'FOREIGN', 'DATA', 'WRAPPER'];