Issue 479: Support for SUBSTRING without a FROM condition, patch from Andrew Franklin

h2/src/docsrc/help/help.csv

@@ -3155,7 +3155,7 @@ CALL UTF8TOSTRING(STRINGTOUTF8('This is a test'))
 Returns a substring of a string starting at a position.
 If the start index is negative, then the start index is relative to the end of the string.
 The length is optional.
-Also supported is: ""SUBSTRING(string FROM start [FOR length])"".
+Also supported is: ""SUBSTRING(string [FROM start] [FOR length])"".
 ","
 CALL SUBSTR('[Hello]', 2, 5);
 CALL SUBSTR('Hello World', -5);

h2/src/docsrc/html/changelog.html

@@ -39,6 +39,7 @@ Change Log
 </li><li>Issue 473: PgServer missing -key option, patch from Andrew Franklin
 </li><li>Issue 471: CREATE VIEW does not check user rights, patch from Andrew Franklin
 </li><li>Issue 477: PgServer binary transmission of query params is unimplemented, patch from Andrew Franklin
+</li><li>Issue 479: Support for SUBSTRING without a FROM condition, patch from Andrew Franklin
 </li></ul>
 
 <h2>Version 1.3.172 (2013-05-25)</h2>

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

@@ -2243,14 +2243,28 @@ public class Parser {
             break;
         }
         case Function.SUBSTRING: {
+            // Different variants include:
+            // SUBSTRING(X,1)
+            // SUBSTRING(X,1,1)
+            // SUBSTRING(X FROM 1 FOR 1) -- Postgres
+            // SUBSTRING(X FROM 1) -- Postgres
+            // SUBSTRING(X FOR 1) -- Postgres
             function.setParameter(0, readExpression());
-            if (!readIf(",")) {
-                read("FROM");
+            if (readIf("FROM")) {
+                function.setParameter(1, readExpression());
+                if (readIf("FOR")) {
+                    function.setParameter(2, readExpression());
                 }
+            } else if (readIf("FOR")) {
+                function.setParameter(1, ValueExpression.get(ValueInt.get(0)));
+                function.setParameter(2, readExpression());
+            } else {
+                read(",");
                 function.setParameter(1, readExpression());
-            if (readIf("FOR") || readIf(",")) {
+                if (readIf(",")) {
                     function.setParameter(2, readExpression());
                 }
+            }
             read(")");
             break;
         }

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

@@ -214,6 +214,9 @@ public class TestCompatibility extends TestBase {
         Statement stat = conn.createStatement();
         stat.execute("SET MODE PostgreSQL");
         testLog(Math.log10(10), stat);
+        
+        assertResult("ABC", stat, "SELECT SUBSTRING('ABCDEF' FOR 3)");
+        assertResult("BCDE", stat, "SELECT SUBSTRING('ABCDEF' FROM 2 FOR 4)");
     }
 
     private void testMySQL() throws SQLException {