Merge pull request #907 from katzyn/join

Nest joins only if required and fix some issues with complex joins

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

@@ -1369,8 +1369,7 @@ public class Parser {
             } else {
                 TableFilter top;
                 top = readTableFilter();
-                top = readJoin(top, false);
-                top = getNested(top);
+                top = readJoin(top);
                 read(")");
                 alias = readFromAlias(null);
                 if (alias != null) {
@@ -1717,8 +1716,7 @@ public class Parser {
         return command;
     }
 
-    private TableFilter readJoin(TableFilter top, boolean nested) {
-        boolean joined = false;
+    private TableFilter readJoin(TableFilter top) {
         TableFilter last = top;
         while (true) {
             TableFilter join;
@@ -1727,47 +1725,46 @@ public class Parser {
                 read("JOIN");
                 // the right hand side is the 'inner' table usually
                 join = readTableFilter();
-                join = readJoin(join, nested);
+                join = readJoin(join);
                 Expression on = null;
                 if (readIf("ON")) {
                     on = readExpression();
                 }
-                top = getNested(top);
-                join.addJoin(top, true, on);
+                addJoin(join, top, true, on);
                 top = join;
             } else if (readIf("LEFT")) {
                 readIf("OUTER");
                 read("JOIN");
                 join = readTableFilter();
-                join = readJoin(join, true);
+                join = readJoin(join);
                 Expression on = null;
                 if (readIf("ON")) {
                     on = readExpression();
                 }
-                top.addJoin(join, true, on);
+                addJoin(top, join, true, on);
             } else if (readIf("FULL")) {
                 throw getSyntaxError();
             } else if (readIf("INNER")) {
                 read("JOIN");
                 join = readTableFilter();
-                top = readJoin(top, false);
+                top = readJoin(top);
                 Expression on = null;
                 if (readIf("ON")) {
                     on = readExpression();
                 }
-                top.addJoin(join, false, on);
+                addJoin(top, join, false, on);
             } else if (readIf("JOIN")) {
                 join = readTableFilter();
-                top = readJoin(top, false);
+                top = readJoin(top);
                 Expression on = null;
                 if (readIf("ON")) {
                     on = readExpression();
                 }
-                top.addJoin(join, false, on);
+                addJoin(top, join, false, on);
             } else if (readIf("CROSS")) {
                 read("JOIN");
                 join = readTableFilter();
-                top.addJoin(join, false, null);
+                addJoin(top, join, false, null);
             } else if (readIf("NATURAL")) {
                 read("JOIN");
                 join = readTableFilter();
@@ -1799,26 +1796,35 @@ public class Parser {
                         }
                     }
                 }
-                top.addJoin(join, false, on);
+                addJoin(top, join, false, on);
             } else {
                 break;
             }
-            joined = true;
             last = join;
         }
-        if (nested && joined) {
-            top = getNested(top);
-        }
         return top;
     }
 
-    private TableFilter getNested(TableFilter n) {
-        String joinTable = Constants.PREFIX_JOIN + parseIndex;
-        TableFilter top = new TableFilter(session, getDualTable(true),
-                joinTable, rightsChecked, currentSelect, n.getOrderInFrom(),
-                null);
-        top.setNestedJoin(n);
-        return top;
+    /**
+     * Add one join to another. This method creates nested join between them if
+     * required.
+     *
+     * @param top parent join
+     * @param join child join
+     * @param outer if child join is an outer join
+     * @param on the join condition
+     * @see TableFilter#addJoin(TableFilter, boolean, Expression)
+     */
+    private void addJoin(TableFilter top, TableFilter join, boolean outer, Expression on) {
+        if (join.getJoin() != null) {
+            String joinTable = Constants.PREFIX_JOIN + parseIndex;
+            TableFilter n = new TableFilter(session, getDualTable(true),
+                    joinTable, rightsChecked, currentSelect, join.getOrderInFrom(),
+                    null);
+            n.setNestedJoin(join);
+            join = n;
+        }
+        top.addJoin(join, outer, on);
     }
 
     private Prepared parseExecute() {
@@ -2149,7 +2155,7 @@ public class Parser {
     }
 
     private void parseJoinTableFilter(TableFilter top, final Select command) {
-        top = readJoin(top, false);
+        top = readJoin(top);
         command.addTableFilter(top, true);
         boolean isOuter = false;
         while (true) {

h2/src/main/org/h2/index/IndexCondition.java

@@ -401,7 +401,7 @@ public class IndexCondition {
         return "column=" + column +
                 ", compareType=" + compareTypeToString(compareType) +
                 ", expression=" + expression +
-                ", expressionList=" + expressionList.toString() +
+                ", expressionList=" + expressionList +
                 ", expressionQuery=" + expressionQuery;
     }
 

h2/src/main/org/h2/index/ViewIndex.java

@@ -168,7 +168,6 @@ public class ViewIndex extends BaseIndex implements SpatialIndex {
 
     private static Query prepareSubQuery(String sql, Session session, int[] masks,
             TableFilter[] filters, int filter, SortOrder sortOrder) {
-        assert filters != null;
         Prepared p;
         session.pushSubQueryInfo(masks, filters, filter, sortOrder);
         try {

h2/src/main/org/h2/table/TableFilter.java

@@ -265,15 +265,34 @@ public class TableFilter implements ColumnResolver {
         if (nestedJoin != null) {
             if (item.getNestedJoinPlan() != null) {
                 nestedJoin.setPlanItem(item.getNestedJoinPlan());
+            } else {
+                nestedJoin.setScanIndexes();
             }
         }
         if (join != null) {
             if (item.getJoinPlan() != null) {
                 join.setPlanItem(item.getJoinPlan());
+            } else {
+                join.setScanIndexes();
             }
         }
     }
 
+    /**
+     * Set all missing indexes to scan indexes recursively.
+     */
+    private void setScanIndexes() {
+        if (index == null) {
+            setIndex(table.getScanIndex(session));
+        }
+        if (join != null) {
+            join.setScanIndexes();
+        }
+        if (nestedJoin != null) {
+            nestedJoin.setScanIndexes();
+        }
+    }
+
     /**
      * Prepare reading rows. This method will remove all index conditions that
      * can not be used, and optimize the conditions.

h2/src/test/org/h2/test/scripts/joins.sql

@@ -103,6 +103,21 @@ select a.i from t1 a inner join (select a.i from t2 a inner join (select i from
 > -
 > rows: 0
 
+insert into t1 values (1);
+> update count: 1
+
+insert into t2 values (1);
+> update count: 1
+
+insert into t3 values (1);
+> update count: 1
+
+select a.i from t1 a inner join (select a.i from t2 a inner join (select i from t3) b on a.i=b.i) b on a.i=b.i;
+> I
+> -
+> 1
+> rows: 1
+
 drop table t1, t2, t3;
 > ok
 
@@ -747,3 +762,32 @@ DROP TABLE B;
 
 DROP TABLE C;
 > ok
+
+CREATE TABLE T1(X1 INT);
+CREATE TABLE T2(X2 INT);
+CREATE TABLE T3(X3 INT);
+CREATE TABLE T4(X4 INT);
+CREATE TABLE T5(X5 INT);
+
+INSERT INTO T1 VALUES (1);
+INSERT INTO T1 VALUES (NULL);
+INSERT INTO T2 VALUES (1);
+INSERT INTO T2 VALUES (NULL);
+INSERT INTO T3 VALUES (1);
+INSERT INTO T3 VALUES (NULL);
+INSERT INTO T4 VALUES (1);
+INSERT INTO T4 VALUES (NULL);
+INSERT INTO T5 VALUES (1);
+INSERT INTO T5 VALUES (NULL);
+
+SELECT T1.X1, T2.X2, T3.X3, T4.X4, T5.X5 FROM (
+  T1 INNER JOIN (
+     T2 LEFT OUTER JOIN (
+       T3 INNER JOIN T4 ON T3.X3 = T4.X4
+     ) ON T2.X2 = T4.X4
+  ) ON T1.X1 = T2.X2
+) INNER JOIN T5 ON T2.X2 = T5.X5;
+> X1 X2 X3 X4 X5
+> -- -- -- -- --
+> 1  1  1  1  1
+> rows: 1

h2/src/test/org/h2/test/synth/TestNestedJoins.java

@@ -380,7 +380,7 @@ public class TestNestedJoins extends TestBase {
         assertTrue(rs.next());
         sql = cleanRemarks(rs.getString(1));
         assertEquals("SELECT DISTINCT T1.A, T2.A, T3.A FROM PUBLIC.T2 " +
-                "LEFT OUTER JOIN ( PUBLIC.T3 LEFT OUTER JOIN ( PUBLIC.T1 ) " +
+                "LEFT OUTER JOIN ( PUBLIC.T3 LEFT OUTER JOIN PUBLIC.T1 " +
                 "ON T1.B = T3.A ) ON T2.B = T1.A", sql);
         rs = stat.executeQuery("select distinct t1.a, t2.a, t3.a from t1 " +
                 "right outer join t3 on t1.b=t3.a " +

h2/src/test/org/h2/test/synth/TestOuterJoins.java

@@ -136,7 +136,7 @@ public class TestOuterJoins extends TestBase {
             s.getConnection().close();
         }
         deleteDerby();
-        deleteDb("nestedJoins");
+        deleteDb("outerJoins");
     }
 
     private void deleteDerby() {
@@ -289,7 +289,7 @@ public class TestOuterJoins extends TestBase {
 
     private void testCases() throws Exception {
 
-        Connection conn = getConnection("nestedJoins");
+        Connection conn = getConnection("outerJoins");
         Statement stat = conn.createStatement();
         ResultSet rs;
         String sql;
@@ -334,7 +334,7 @@ public class TestOuterJoins extends TestBase {
         sql = cleanRemarks(rs.getString(1));
         assertEquals("SELECT DISTINCT T1.A, T2.A, T3.A FROM PUBLIC.T2 " +
                 "LEFT OUTER JOIN ( PUBLIC.T3 " +
-                "LEFT OUTER JOIN ( PUBLIC.T1 ) ON T1.B = T3.A ) " +
+                "LEFT OUTER JOIN PUBLIC.T1 ON T1.B = T3.A ) " +
                 "ON T2.B = T1.A", sql);
         rs = stat.executeQuery("select distinct t1.a, t2.a, t3.a from t1 " +
                 "right outer join t3 on t1.b=t3.a right outer join t2 on t2.b=t1.a");
@@ -571,7 +571,7 @@ public class TestOuterJoins extends TestBase {
         // }
 
         conn.close();
-        deleteDb("nestedJoins");
+        deleteDb("outerJoins");
     }
 
     private static String cleanRemarks(String sql) {