[#285] Add support for ALTER INDEX IF EXISTS

h2/src/docsrc/help/help.csv

@@ -192,7 +192,7 @@ SHOW TABLES
 "
 
 "Commands (DDL)","ALTER INDEX RENAME","
-ALTER INDEX indexName RENAME TO newIndexName
+ALTER INDEX [ IF EXISTS ] indexName RENAME TO newIndexName
 ","
 Renames an index.
 This command commits an open transaction in this connection.

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

@@ -4852,10 +4852,13 @@ public class Parser {
     }
 
     private AlterIndexRename parseAlterIndex() {
+        boolean ifExists = readIfExists(false);
         String indexName = readIdentifierWithSchema();
         Schema old = getSchema();
         AlterIndexRename command = new AlterIndexRename(session);
-        command.setOldIndex(getSchema().getIndex(indexName));
+        command.setOldSchema(old);
+        command.setOldName(indexName);
+        command.setIfExists(ifExists);
         read("RENAME");
         read("TO");
         String newName = readIdentifierWithSchema(old.getName());

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

@@ -20,6 +20,9 @@ import org.h2.schema.Schema;
  */
 public class AlterIndexRename extends DefineCommand {
 
+    private boolean ifExists;
+    private Schema oldSchema;
+    private String oldIndexName;
     private Index oldIndex;
     private String newIndexName;
 
@@ -27,8 +30,16 @@ public class AlterIndexRename extends DefineCommand {
         super(session);
     }
 
-    public void setOldIndex(Index index) {
-        oldIndex = index;
+    public void setIfExists(boolean b) {
+        ifExists = b;
+    }
+
+    public void setOldSchema(Schema old) {
+        oldSchema = old;
+    }
+
+    public void setOldName(String name) {
+        oldIndexName = name;
     }
 
     public void setNewName(String name) {
@@ -39,9 +50,17 @@ public class AlterIndexRename extends DefineCommand {
     public int update() {
         session.commit(true);
         Database db = session.getDatabase();
-        Schema schema = oldIndex.getSchema();
-        if (schema.findIndex(session, newIndexName) != null ||
-                newIndexName.equals(oldIndex.getName())) {
+        oldIndex = oldSchema.findIndex(session, oldIndexName);
+        if (oldIndex == null) {
+            if (!ifExists) {
+                throw DbException.get(ErrorCode.INDEX_NOT_FOUND_1,
+                        newIndexName);
+            } else {
+                return 0;
+            }
+        }
+        if (oldSchema.findIndex(session, newIndexName) != null ||
+                newIndexName.equals(oldIndexName)) {
             throw DbException.get(ErrorCode.INDEX_ALREADY_EXISTS_1,
                     newIndexName);
         }

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

@@ -67,7 +67,7 @@ SHOW { SCHEMAS | TABLES [ FROM schemaName ] |
 ","
 Lists the schemas, tables, or the columns of a table."
 "Commands (DDL)","ALTER INDEX RENAME","
-ALTER INDEX indexName RENAME TO newIndexName
+ALTER INDEX [ IF EXISTS ] indexName RENAME TO newIndexName
 ","
 Renames an index."
 "Commands (DDL)","ALTER SCHEMA RENAME","

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

@@ -4458,7 +4458,13 @@ create index if not exists idx_id on s.test(id);
 create index if not exists idx_id on s.test(id);
 > ok
 
-alter index s.idx_id rename to s.index_id;
+alter index s.idx_id rename to s.x;
+> ok
+
+alter index if exists s.idx_id rename to s.x;
+> ok
+
+alter index if exists s.x rename to s.index_id;
 > ok
 
 alter sequence if exists s.seq restart with 10;