Add IDENTITY() and SCOPE_IDENTITY() to LEGACY mode

h2/src/docsrc/html/changelog.html

@@ -21,6 +21,8 @@ <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
 <ul>
+<li>PR #3381: Add IDENTITY() and SCOPE_IDENTITY() to LEGACY mode
+</li>
 <li>Issue #3376: Data cannot be read after insert of clob data > MAX_LENGTH_INPLACE_LOB with data change delta table
 </li>
 <li>PR #3377: Add -webExternalNames setting and fix WebServer.getConnection()

h2/src/docsrc/html/features.html

@@ -883,6 +883,7 @@ <h3>LEGACY Compatibility Mode</h3>
 </li><li>Attempt to reference a non-unique set of columns from a referential constraint
 will create an UNIQUE constraint on them automatically.
 </li><li>Unsafe comparison operators between numeric and boolean values are allowed.
+</li><li>IDENTITY() and SCOPE_IDENTITY() are supported, but both are implemented like SCOPE_IDENTITY()
 </li></ul>
 
 <h3>DB2 Compatibility Mode</h3>

h2/src/main/org/h2/engine/Mode.java

@@ -478,6 +478,7 @@ public enum CharPadding {
         // Legacy identity and sequence features
         mode.identityClause = true;
         mode.updateSequenceOnManualIdentityInsertion = true;
+        mode.takeInsertedIdentity = true;
         mode.identityColumnsHaveDefaultOnNull = true;
         mode.nextvalAndCurrvalPseudoColumns = true;
         // Legacy DML features

h2/src/main/org/h2/mode/FunctionsLegacy.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2004-2022 H2 Group. Multiple-Licensed under the MPL 2.0,
+ * and the EPL 1.0 (https://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.mode;
+
+import java.util.HashMap;
+
+import org.h2.engine.SessionLocal;
+import org.h2.expression.Expression;
+import org.h2.message.DbException;
+import org.h2.value.TypeInfo;
+import org.h2.value.Value;
+
+/**
+ * This class implements some legacy functions not available in Regular mode.
+ */
+public class FunctionsLegacy extends ModeFunction {
+
+    private static final HashMap<String, FunctionInfo> FUNCTIONS = new HashMap<>();
+
+    private static final int IDENTITY = 6001;
+
+    private static final int SCOPE_IDENTITY = IDENTITY + 1;
+
+    static {
+        FUNCTIONS.put("IDENTITY", new FunctionInfo("IDENTITY", IDENTITY, 0, Value.BIGINT, true, false));
+        FUNCTIONS.put("SCOPE_IDENTITY",
+                new FunctionInfo("SCOPE_IDENTITY", SCOPE_IDENTITY, 0, Value.BIGINT, true, false));
+    }
+
+    /**
+     * Returns mode-specific function for a given name, or {@code null}.
+     *
+     * @param upperName
+     *            the upper-case name of a function
+     * @return the function with specified name or {@code null}
+     */
+    public static FunctionsLegacy getFunction(String upperName) {
+        FunctionInfo info = FUNCTIONS.get(upperName);
+        if (info != null) {
+            return new FunctionsLegacy(info);
+        }
+        return null;
+    }
+
+    private FunctionsLegacy(FunctionInfo info) {
+        super(info);
+    }
+
+    @Override
+    public Value getValue(SessionLocal session) {
+        switch (info.type) {
+        case IDENTITY:
+        case SCOPE_IDENTITY:
+            return session.getLastIdentity().convertTo(type);
+        default:
+            throw DbException.getInternalError("type=" + info.type);
+        }
+    }
+
+    @Override
+    public Expression optimize(SessionLocal session) {
+        type = TypeInfo.getTypeInfo(info.returnDataType);
+        return this;
+    }
+
+}

h2/src/main/org/h2/mode/ModeFunction.java

@@ -49,6 +49,8 @@ public static ModeFunction getFunction(Database database, String name) {
 
     private static ModeFunction getCompatibilityModeFunction(String name, ModeEnum modeEnum) {
         switch (modeEnum) {
+        case LEGACY:
+            return FunctionsLegacy.getFunction(name);
         case DB2:
         case Derby:
             return FunctionsDB2Derby.getFunction(name);

h2/src/test/org/h2/test/scripts/TestScript.java

@@ -206,7 +206,7 @@ public void test() throws Exception {
                 "file-read", "file-write", "greatest", "h2version", "identity",
                 "ifnull", "last-insert-id", "least", "link-schema", "lock-mode", "lock-timeout",
                 "memory-free", "memory-used", "nextval", "nullif", "nvl2",
-                "readonly", "rownum", "scope-identity", "session-id",
+                "readonly", "rownum", "session-id",
                 "table", "transaction-id", "trim_array", "truncate-value", "unnest" }) {
             testScript("functions/system/" + s + ".sql");
         }

h2/src/test/org/h2/test/scripts/functions/system/identity.sql

@@ -2,3 +2,33 @@
 -- and the EPL 1.0 (https://h2database.com/html/license.html).
 -- Initial Developer: H2 Group
 --
+
+CREATE TABLE TEST(ID BIGINT GENERATED BY DEFAULT AS IDENTITY, V INT);
+> ok
+
+INSERT INTO TEST(V) VALUES 10;
+> update count: 1
+
+VALUES IDENTITY();
+> exception FUNCTION_NOT_FOUND_1
+
+VALUES SCOPE_IDENTITY();
+> exception FUNCTION_NOT_FOUND_1
+
+SET MODE LEGACY;
+> ok
+
+INSERT INTO TEST(V) VALUES 20;
+> update count: 1
+
+VALUES IDENTITY();
+>> 2
+
+VALUES SCOPE_IDENTITY();
+>> 2
+
+SET MODE REGULAR;
+> ok
+
+DROP TABLE TEST;
+> ok