Merge pull request #1571 from isuruperera/master

Optimizing ConditionAndOr queries

h2/src/main/org/h2/expression/condition/ConditionAndOr.java

@@ -159,8 +159,7 @@ public class ConditionAndOr extends Condition {
                 }
             }
         }
-        // TODO optimization: convert ((A=1 AND B=2) OR (A=1 AND B=3)) to
-        // (A=1 AND (B=2 OR B=3))
+
         if (andOrType == OR &&
                 session.getDatabase().getSettings().optimizeOr) {
             // try to add conditions (A=B AND B=1: add A=1)
@@ -201,6 +200,14 @@ public class ConditionAndOr extends Condition {
                 if (added != null) {
                     return added.optimize(session);
                 }
+            } else if (left instanceof ConditionAndOr &&
+                    right instanceof ConditionAndOr ){
+                ConditionAndOr condAORight = (ConditionAndOr)right;
+                ConditionAndOr condAORLeft = (ConditionAndOr)left;
+                Expression reduced = optimizeConditionAndOr(condAORLeft,condAORight);
+                if(reduced != null){
+                    return reduced.optimize(session);
+                }
             }
         }
         // TODO optimization: convert .. OR .. to UNION if the cost is lower
@@ -304,4 +311,34 @@ public class ConditionAndOr extends Condition {
         }
     }
 
+    /**
+     * Optimize query according to the given condition. Example:
+     * (A AND B) OR (C AND B), the new condition B AND (A OR C) is returned
+     *
+     * @param left the session
+     * @param right the second condition
+     * @return null or the third condition
+     */
+    private Expression optimizeConditionAndOr(ConditionAndOr left, ConditionAndOr right) {
+        if (left.andOrType != AND || right.andOrType != AND) {
+            return null;
+        }
+        Expression commonExpressionLeft = left.getSubexpression(0);
+        Expression commonExpressionRight = left.getSubexpression(1);
+        Expression combinedExpression;
+        if (left.getSubexpression(0).getSQL().equals(right.getSubexpression(0).getSQL())) {
+            combinedExpression = new ConditionAndOr(OR, left.getSubexpression(1), right.getSubexpression(1));
+            return new ConditionAndOr(AND, commonExpressionLeft, combinedExpression);
+        } else if (left.getSubexpression(0).getSQL().equals(right.getSubexpression(1).getSQL())) {
+            combinedExpression = new ConditionAndOr(OR, left.getSubexpression(1), right.getSubexpression(0));
+            return new ConditionAndOr(AND, commonExpressionLeft, combinedExpression);
+        } else if (left.getSubexpression(1).getSQL().equals(right.getSubexpression(0).getSQL())) {
+            combinedExpression = new ConditionAndOr(OR, left.getSubexpression(0), right.getSubexpression(1));
+            return new ConditionAndOr(AND, commonExpressionRight, combinedExpression);
+        } else if (left.getSubexpression(1).getSQL().equals(right.getSubexpression(1).getSQL())) {
+            combinedExpression = new ConditionAndOr(OR, left.getSubexpression(0), right.getSubexpression(0));
+            return new ConditionAndOr(AND, commonExpressionRight, combinedExpression);
+        }
+        return null;
+    }
 }

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

@@ -84,6 +84,7 @@ public class TestOptimizations extends TestDb {
         testOrderedIndexes();
         testIndexUseDespiteNullsFirst();
         testConvertOrToIn();
+        testConditionAndOrDistributiveLaw();
         deleteDb("optimizations");
     }
 
@@ -1177,4 +1178,30 @@ public class TestOptimizations extends TestDb {
         assertContains(rs.getString(1), "/* PUBLIC.TABLE_B_IDX");
         conn.close();
     }
+
+    private void testConditionAndOrDistributiveLaw() throws SQLException {
+        deleteDb("optimizations");
+        Connection conn = getConnection("optimizations");
+        Statement stat = conn.createStatement();
+        stat.execute("CREATE TABLE IF NOT EXISTS TABLE_A (" +
+                "id int(10) NOT NULL AUTO_INCREMENT, " +
+                "name VARCHAR(30) NOT NULL," +
+                "occupation VARCHAR(20)," +
+                "age int(10)," +
+                "salary int(10)," +
+                "PRIMARY KEY(id))");
+        stat.execute("INSERT INTO TABLE_A (name,occupation,age,salary) VALUES" +
+                "('mark', 'doctor',25,5000)," +
+                "('kevin', 'artist',20,4000)," +
+                "('isuru', 'engineer',25,5000)," +
+                "('josaph', 'businessman',30,7000)," +
+                "('sajeewa', 'analyst',24,5000)," +
+                "('randil', 'engineer',25,5000)," +
+                "('ashan', 'developer',24,5000)");
+        ResultSet rs = stat.executeQuery("SELECT * FROM TABLE_A WHERE (salary = 5000 AND name = 'isuru') OR" +
+                "(age = 25 AND name = 'isuru') ");
+        rs.next();
+        assertTrue("engineer".equals(rs.getString("occupation")));
+        conn.close();
+    }
 }