Improved Oracle compatibility: support for NVL2. Thanks to litailang for the patch!

h2/src/docsrc/help/help.csv

@@ -3337,7 +3337,7 @@ CAST(CAST('FFFF' AS BINARY) AS INT);
 "
 
 "Functions (System)","COALESCE","
-COALESCE(aValue, bValue [,...])
+{ COALESCE | NVL } (aValue, bValue [,...])
 ","
 Returns the first value that is not null.
 ","
@@ -3565,6 +3565,14 @@ Returns NULL if 'a' is equals to 'b', otherwise 'a'.
 NULLIF(A, B)
 "
 
+"Functions (System)","NVL2","
+NVL2(testValue, aValue, bValue)
+","
+If the test value is null, then 'b' is returned. Otherwise, 'a' is returned.
+","
+NVL2(X, 'not null', 'null')
+"
+
 "Functions (System)","READONLY","
 READONLY()
 ","

h2/src/docsrc/html/changelog.html

@@ -17,7 +17,8 @@ Change Log
 
 <h1>Change Log</h1>
 <h2>Next Version (unreleased)</h2>
-<ul><li>Improved PostgreSQL compatibility: support for RANDOM() in addition to RAND().
+<ul><li>Improved Oracle compatibility: support for NVL2. Thanks to litailang for the patch!
+</li><li>Improved PostgreSQL compatibility: support for RANDOM() in addition to RAND().
 </li><li>There was a classloader memory leak problem because a class contained a static
     references to an exception (including stack trace).
 </li><li>Split file system: truncating a file now deletes the parts in reverse order,

h2/src/main/org/h2/expression/Function.java

@@ -95,7 +95,7 @@ public class Function extends Expression implements FunctionCall {
             CASE = 206, NEXTVAL = 207, CURRVAL = 208, ARRAY_GET = 209, CSVREAD = 210, CSVWRITE = 211,
             MEMORY_FREE = 212, MEMORY_USED = 213, LOCK_MODE = 214, SCHEMA = 215, SESSION_ID = 216, ARRAY_LENGTH = 217,
             LINK_SCHEMA = 218, GREATEST = 219, LEAST = 220, CANCEL_SESSION = 221, SET = 222, TABLE = 223, TABLE_DISTINCT = 224,
-            FILE_READ = 225, TRANSACTION_ID = 226, TRUNCATE_VALUE = 227;
+            FILE_READ = 225, TRANSACTION_ID = 226, TRUNCATE_VALUE = 227, NVL2 = 228;
 
     private static final int VAR_ARGS = -1;
     private static final long PRECISION_UNKNOWN = -1;
@@ -301,6 +301,7 @@ public class Function extends Expression implements FunctionCall {
         addFunctionWithNull("TRUNCATE_VALUE", TRUNCATE_VALUE, 3, Value.NULL);
         addFunctionWithNull("COALESCE", COALESCE, VAR_ARGS, Value.NULL);
         addFunctionWithNull("NVL", COALESCE, VAR_ARGS, Value.NULL);
+        addFunctionWithNull("NVL2", NVL2, 3, Value.NULL);
         addFunctionWithNull("NULLIF", NULLIF, 2, Value.NULL);
         addFunctionWithNull("CASE", CASE, VAR_ARGS, Value.NULL);
         addFunctionNotDeterministic("NEXTVAL", NEXTVAL, VAR_ARGS, Value.LONG);
@@ -753,6 +754,17 @@ public class Function extends Expression implements FunctionCall {
             result = v.convertTo(dataType);
             break;
         }
+        case NVL2: {
+            Expression expr;
+            if (v0 == ValueNull.INSTANCE) {
+                expr = argList[2];
+            } else {
+               	expr = argList[1];
+            }
+            Value v = expr.getValue(session);
+            result = v.convertTo(dataType);
+            break;
+        }
         case COALESCE: {
             result = v0;
             for (int i = 0; i < argList.length; i++) {
@@ -1677,6 +1689,7 @@ public class Function extends Expression implements FunctionCall {
             break;
         }
         case CASEWHEN:
+        case NVL2:
             t = Value.getHigherOrder(args[1].getType(), args[2].getType());
             p = Math.max(args[1].getPrecision(), args[2].getPrecision());
             d = Math.max(args[1].getDisplaySize(), args[2].getDisplaySize());

h2/src/test/org/h2/test/db/TestFunctions.java

@@ -25,6 +25,7 @@ import java.util.Properties;
 import java.util.UUID;
 
 import org.h2.api.AggregateFunction;
+import org.h2.jdbc.JdbcSQLException;
 import org.h2.test.TestBase;
 import org.h2.tools.SimpleResultSet;
 import org.h2.util.IOUtils;
@@ -66,10 +67,60 @@ public class TestFunctions extends TestBase implements AggregateFunction {
         testFunctions();
         testFileRead();
         testValue();
+        testNvl2();
         deleteDb("functions");
         IOUtils.deleteRecursive(TEMP_DIR, true);
     }
 
+    private void testNvl2() throws SQLException {
+        Connection conn = getConnection("functions");
+        Statement stat = conn.createStatement();
+
+        String createSQL = "CREATE TABLE testNvl2 (id BIGINT,txt1 varchar,txt2 varchar,num number(9,0));";
+        stat.execute(createSQL);
+        stat.execute("insert into testNvl2(id,txt1,txt2,num) values (1,'test1','test2',null)");
+        stat.execute("insert into testNvl2(id,txt1,txt2,num) values (2,null,'test4',null)");
+        stat.execute("insert into testNvl2(id,txt1,txt2,num) values (3,'test5',null,null)");
+        stat.execute("insert into testNvl2(id,txt1,txt2,num) values (4,null,null,null)");
+        stat.execute("insert into testNvl2(id,txt1,txt2,num) values (5,'2',null,1)");
+        stat.execute("insert into testNvl2(id,txt1,txt2,num) values (6,'2',null,null)");
+        stat.execute("insert into testNvl2(id,txt1,txt2,num) values (7,'test2',null,null)");
+
+        String query = "SELECT NVL2(txt1, txt1, txt2), txt1 FROM testNvl2 order by id asc";
+        ResultSet rs = stat.executeQuery(query);
+        rs.next();
+        String actual = rs.getString(1);
+        assertEquals("test1", actual);
+        rs.next();
+        actual = rs.getString(1);
+        assertEquals("test4", actual);
+        rs.next();
+        actual = rs.getString(1);
+        assertEquals("test5", actual);
+        rs.next();
+        actual = rs.getString(1);
+        assertEquals(null, actual);
+        assertEquals(rs.getMetaData().getColumnType(2), rs.getMetaData().getColumnType(1));
+        rs.close();
+
+        rs = stat.executeQuery("SELECT NVL2(num, num, txt1), num FROM testNvl2 where id in (5,6) order by id asc");
+        rs.next();
+        assertEquals(rs.getMetaData().getColumnType(2), rs.getMetaData().getColumnType(1));
+
+        try {
+            rs = stat.executeQuery("SELECT NVL2(num, num, txt1), num FROM testNvl2 where id = 7 order by id asc");
+        } catch (JdbcSQLException e) {
+            Throwable t = e.getCause();
+            if (t instanceof NumberFormatException) {
+                //
+            } else {
+                throw e;
+            }
+        }
+
+        conn.close();
+    }
+
     private void testValue() throws SQLException {
         Connection conn = getConnection("functions");
         Statement stat = conn.createStatement();