[#285] Add support for ALTER VIEW IF EXISTS

h2/src/docsrc/help/help.csv

@@ -380,7 +380,7 @@ ALTER USER SA SET PASSWORD 'rioyxlgt'
 "
 
 "Commands (DDL)","ALTER VIEW","
-ALTER VIEW viewName RECOMPILE
+ALTER VIEW [ IF EXISTS ] viewName RECOMPILE
 ","
 Recompiles a view after the underlying tables have been changed or created.
 This command is used for views created using CREATE FORCE VIEW.

h2/src/main/org/h2/command/Parser.java

@@ -4866,9 +4866,11 @@ public class Parser {
 
     private AlterView parseAlterView() {
         AlterView command = new AlterView(session);
+        boolean ifExists = readIfExists(false);
+        command.setIfExists(ifExists);
         String viewName = readIdentifierWithSchema();
         Table tableView = getSchema().findTableOrView(session, viewName);
-        if (!(tableView instanceof TableView)) {
+        if (!(tableView instanceof TableView) && !ifExists) {
             throw DbException.get(ErrorCode.VIEW_NOT_FOUND_1, viewName);
         }
         TableView view = (TableView) tableView;

h2/src/main/org/h2/command/ddl/AlterView.java

@@ -17,12 +17,17 @@ import org.h2.table.TableView;
  */
 public class AlterView extends DefineCommand {
 
+    private boolean ifExists;
     private TableView view;
 
     public AlterView(Session session) {
         super(session);
     }
 
+    public void setIfExists(boolean b) {
+        ifExists = b;
+    }
+
     public void setView(TableView view) {
         this.view = view;
     }
@@ -30,6 +35,9 @@ public class AlterView extends DefineCommand {
     @Override
     public int update() {
         session.commit(true);
+        if (view == null && ifExists) {
+            return 0;
+        }
         session.getUser().checkRight(view, Right.ALL);
         DbException e = view.recompile(session, false, true);
         if (e != null) {

h2/src/main/org/h2/res/help.csv

@@ -138,7 +138,7 @@ ALTER USER userName SET { PASSWORD string | SALT bytes HASH bytes }
 ","
 Changes the password of a user."
 "Commands (DDL)","ALTER VIEW","
-ALTER VIEW viewName RECOMPILE
+ALTER VIEW [ IF EXISTS ] viewName RECOMPILE
 ","
 Recompiles a view after the underlying tables have been changed or created."
 "Commands (DDL)","ANALYZE","

h2/src/test/org/h2/test/testScript.sql

@@ -2991,6 +2991,12 @@ CREATE memory TABLE ADDRESS(ID INT);
 alter view address_view recompile;
 > ok
 
+alter view if exists address_view recompile;
+> ok
+
+alter view if exists doesnt_exist recompile;
+> ok
+
 select * from ADDRESS_VIEW;
 > ID
 > --