Support for ROW_NUMBER() OVER() as an alias for ROWNUM() for compatibility with…

Support for ROW_NUMBER() OVER() as an alias for ROWNUM() for compatibility with PostgreSQL and Apache Derby.

h2/src/docsrc/help/help.csv

@@ -3627,11 +3627,11 @@ READONLY()
 "
 
 "Functions (System)","ROWNUM","
-ROWNUM()
+{ ROWNUM() } | { ROW_NUMBER() OVER() } 
 ","
 Returns the number of the current row.
-This method returns an int.
-This function is supported for SELECT statements, as well as for DELETE and UPDATE.
+This method returns a long.
+It is supported for SELECT statements, as well as for DELETE and UPDATE.
 The first row has the row number 1, and is calculated before ordering and grouping the result set,
 but after evaluating index conditions (even when the  index conditions are specified in an outer query).
 To get the row number after ordering and grouping, use a subquery.

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

@@ -2275,6 +2275,12 @@ public class Parser {
             tf.setColumns(columns);
             break;
         }
+        case Function.ROW_NUMBER:
+            read(")");
+            read("OVER");
+            read("(");
+            read(")");
+            return new Rownum(currentSelect == null ? currentPrepared : currentSelect);
         default:
             if (!readIf(")")) {
                 int i = 0;

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

@@ -97,6 +97,8 @@ public class Function extends Expression implements FunctionCall {
             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, NVL2 = 228;
 
+    public static final int ROW_NUMBER = 300;
+
     private static final int VAR_ARGS = -1;
     private static final long PRECISION_UNKNOWN = -1;
 
@@ -336,6 +338,9 @@ public class Function extends Expression implements FunctionCall {
         // TableFunction
         addFunctionWithNull("TABLE", TABLE, VAR_ARGS, Value.RESULT_SET);
         addFunctionWithNull("TABLE_DISTINCT", TABLE_DISTINCT, VAR_ARGS, Value.RESULT_SET);
+
+        // pseudo function
+        addFunctionWithNull("ROW_NUMBER", ROW_NUMBER, 0, Value.LONG);
     }
 
     protected Function(Database database, FunctionInfo info) {

h2/src/test/org/h2/test/test-1.3.txt

 --- special grammar and test cases ---------------------------------------------------------------------------------------------
+create table test(id int primary key, name varchar(255), row_number int);
+> ok
+
+insert into test values(1, 'hello', 10), (2, 'world', 20);
+> update count: 2
+
+select row_number() over(), id, name from test order by id;
+> ROWNUM() ID NAME
+> -------- -- -----
+> 1        1  hello
+> 2        2  world
+> rows (ordered): 2
+
+select row_number() over(), id, name from test order by name;
+> ROWNUM() ID NAME
+> -------- -- -----
+> 1        1  hello
+> 2        2  world
+> rows (ordered): 2
+
+select row_number() over(), id, name from test order by name desc;
+> ROWNUM() ID NAME
+> -------- -- -----
+> 2        2  world
+> 1        1  hello
+> rows (ordered): 2
+
+drop table test;
+> ok
+
 create table test(x int) as select x from system_range(1, 2);
 > ok