Experimental feature to support nested joins.

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

@@ -124,6 +124,7 @@ import org.h2.table.RangeTable;
 import org.h2.table.Table;
 import org.h2.table.TableFilter;
 import org.h2.table.TableView;
+import org.h2.table.TableFilter.TableFilterVisitor;
 import org.h2.util.Utils;
 import org.h2.util.MathUtils;
 import org.h2.util.New;
@@ -969,8 +970,17 @@ public class Parser {
                 alias = session.getNextSystemIdentifier(sqlCommand);
                 table = TableView.createTempView(s, session.getUser(), alias, query, currentSelect);
             } else {
-                TableFilter top = readTableFilter(fromOuter);
-                top = readJoin(top, currentSelect, fromOuter);
+                TableFilter top;
+                if (SysProperties.NESTED_JOINS) {
+                    String joinTable = Constants.PREFIX_JOIN + parseIndex;
+                    top = new TableFilter(session, getDualTable(true), joinTable, rightsChecked, currentSelect);
+                    TableFilter n = readTableFilter(false);
+                    n = readJoin(n, currentSelect, false);
+                    top.addJoin(n, false, true, null);
+                } else {
+                    top = readTableFilter(fromOuter);
+                    top = readJoin(top, currentSelect, fromOuter);
+                }
                 read(")");
                 alias = readFromAlias(null);
                 if (alias != null) {
@@ -988,7 +998,7 @@ public class Parser {
                     read(",");
                     Expression max = readExpression();
                     read(")");
-                    table = new RangeTable(mainSchema, min, max);
+                    table = new RangeTable(mainSchema, min, max, false);
                 } else {
                     Expression func = readFunction(schema, tableName);
                     if (!(func instanceof FunctionCall)) {
@@ -997,7 +1007,7 @@ public class Parser {
                     table = new FunctionTable(mainSchema, session, func, (FunctionCall) func);
                 }
             } else if (equalsToken("DUAL", tableName)) {
-                table = getDualTable();
+                table = getDualTable(false);
             } else {
                 table = readTableOrView(tableName);
             }
@@ -1233,7 +1243,14 @@ public class Parser {
                 if (readIf("ON")) {
                     on = readExpression();
                 }
-                newTop.addJoin(top, true, fromOuter, on);
+                if (SysProperties.NESTED_JOINS) {
+                    String joinTable = Constants.PREFIX_JOIN + parseIndex;
+                    TableFilter nt = new TableFilter(session, getDualTable(true), joinTable, rightsChecked, currentSelect);
+                    nt.addJoin(top, false, true, null);
+                    newTop.addJoin(nt, true, false, on);
+                } else {
+                    newTop.addJoin(top, true, false, on);
+                }
                 top = newTop;
                 last = newTop;
             } else if (readIf("LEFT")) {
@@ -1245,7 +1262,7 @@ public class Parser {
                 if (readIf("ON")) {
                     on = readExpression();
                 }
-                top.addJoin(join, true, fromOuter, on);
+                top.addJoin(join, true, false, on);
                 last = join;
             } else if (readIf("FULL")) {
                 throw getSyntaxError();
@@ -1258,9 +1275,9 @@ public class Parser {
                     on = readExpression();
                 }
                 if (SysProperties.NESTED_JOINS) {
-                    top.addJoin(join, false, fromOuter, on);
+                    top.addJoin(join, false, false, on);
                 } else {
-                    top.addJoin(join, fromOuter, fromOuter, on);
+                    top.addJoin(join, fromOuter, false, on);
                 }
                 last = join;
             } else if (readIf("JOIN")) {
@@ -1271,18 +1288,18 @@ public class Parser {
                     on = readExpression();
                 }
                 if (SysProperties.NESTED_JOINS) {
-                    top.addJoin(join, false, fromOuter, on);
+                    top.addJoin(join, false, false, on);
                 } else {
-                    top.addJoin(join, fromOuter, fromOuter, on);
+                    top.addJoin(join, fromOuter, false, on);
                 }
                 last = join;
             } else if (readIf("CROSS")) {
                 read("JOIN");
                 TableFilter join = readTableFilter(fromOuter);
                 if (SysProperties.NESTED_JOINS) {
-                    top.addJoin(join, false, fromOuter, null);
+                    top.addJoin(join, false, false, null);
                 } else {
-                    top.addJoin(join, fromOuter, fromOuter, null);
+                    top.addJoin(join, fromOuter, false, null);
                 }
                 last = join;
             } else if (readIf("NATURAL")) {
@@ -1313,9 +1330,9 @@ public class Parser {
                     }
                 }
                 if (SysProperties.NESTED_JOINS) {
-                    top.addJoin(join, false, fromOuter, on);
+                    top.addJoin(join, false, false, on);
                 } else {
-                    top.addJoin(join, fromOuter, fromOuter, on);
+                    top.addJoin(join, fromOuter, false, on);
                 }
                 last = join;
             } else {
@@ -1558,16 +1575,18 @@ public class Parser {
         } while (readIf(","));
     }
 
-    private void parseJoinTableFilter(TableFilter top, Select command) {
+    private void parseJoinTableFilter(TableFilter top, final Select command) {
         top = readJoin(top, command, top.isJoinOuter());
         command.addTableFilter(top, true);
         boolean isOuter = false;
         while (true) {
-            for (TableFilter n = top.getNestedJoin(); n != null; n = n.getNestedJoin()) {
-                command.addTableFilter(n, false);
-                for (TableFilter j = n.getJoin(); j != null; j = j.getJoin()) {
-                    command.addTableFilter(j, false);
-                }
+            TableFilter n = top.getNestedJoin();
+            if (n != null) {
+                n.visit(new TableFilterVisitor() {
+                    public void accept(TableFilter f) {
+                        command.addTableFilter(f, false);
+                    }
+                });
             }
             TableFilter join = top.getJoin();
             if (join == null) {
@@ -1652,7 +1671,7 @@ public class Parser {
             if (!readIf("FROM")) {
                 // select without FROM: convert to SELECT ... FROM
                 // SYSTEM_RANGE(1,1)
-                Table dual = getDualTable();
+                Table dual = getDualTable(false);
                 TableFilter filter = new TableFilter(session, dual, null, rightsChecked, currentSelect);
                 command.addTableFilter(filter, true);
             } else {
@@ -1688,10 +1707,10 @@ public class Parser {
         return command;
     }
 
-    private Table getDualTable() {
+    private Table getDualTable(boolean noColumns) {
         Schema main = database.findSchema(Constants.SCHEMA_MAIN);
         Expression one = ValueExpression.get(ValueLong.get(1));
-        return new RangeTable(main, one, one);
+        return new RangeTable(main, one, one, noColumns);
     }
 
     private void setSQL(Prepared command, String start, int startIndex) {

h2/src/main/org/h2/command/dml/Select.java

@@ -845,27 +845,35 @@ public class Select extends Query {
         optimizer.optimize();
         topTableFilter = optimizer.getTopFilter();
         double planCost = optimizer.getCost();
-        
+
         setEvaluatableRecursive(topTableFilter);
 
         topTableFilter.prepare();
         return planCost;
     }
-    
+
     private void setEvaluatableRecursive(TableFilter f) {
         for (; f != null; f = f.getJoin()) {
             f.setEvaluatable(f, true);
             if (condition != null) {
                 condition.setEvaluatable(f, true);
             }
+            TableFilter n = f.getNestedJoin();
+            if (n != null) {
+                setEvaluatableRecursive(n);
+            }
             Expression on = f.getJoinCondition();
             if (on != null) {
                 if (!on.isEverything(ExpressionVisitor.EVALUATABLE)) {
-                    if (f.isJoinOuter()) {
-                        // this will check if all columns exist - it may or may not throw an exception
-                        on = on.optimize(session);
-                        // it is not supported even if the columns exist
-                        throw DbException.get(ErrorCode.UNSUPPORTED_OUTER_JOIN_CONDITION_1, on.getSQL());
+                    if (SysProperties.NESTED_JOINS) {
+                        int testCanSupport;
+                    } else {
+                        if (f.isJoinOuter()) {
+                            // this will check if all columns exist - it may or may not throw an exception
+                            on = on.optimize(session);
+                            // it is not supported even if the columns exist
+                            throw DbException.get(ErrorCode.UNSUPPORTED_OUTER_JOIN_CONDITION_1, on.getSQL());
+                        }
                     }
                     f.removeJoinCondition();
                     // need to check that all added are bound to a table
@@ -885,10 +893,6 @@ public class Select extends Query {
             for (Expression e : expressions) {
                 e.setEvaluatable(f, true);
             }
-            TableFilter n = f.getNestedJoin();
-            if (n != null) {
-                setEvaluatableRecursive(n);
-            }
         }
     }
 

h2/src/main/org/h2/engine/Constants.java

@@ -222,6 +222,11 @@ public class Constants {
      */
     public static final String PREFIX_INDEX = "INDEX_";
 
+    /**
+     * The name prefix used for synthetic nested join tables.
+     */
+    public static final String PREFIX_JOIN = "SYSTEM_JOIN_";
+
     /**
      * The name prefix used for primary key constraints that are not explicitly
      * named.

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

@@ -11,6 +11,7 @@ import org.h2.command.Parser;
 import org.h2.command.dml.Select;
 import org.h2.command.dml.SelectListColumnResolver;
 import org.h2.constant.ErrorCode;
+import org.h2.constant.SysProperties;
 import org.h2.engine.Database;
 import org.h2.engine.Session;
 import org.h2.index.IndexCondition;
@@ -244,6 +245,12 @@ public class ExpressionColumn extends Expression {
             // if the current value is known (evaluatable set)
             // or if this columns belongs to a 'higher level' query and is
             // therefore just a parameter
+            if (SysProperties.NESTED_JOINS) {
+                if (getTableFilter() == null) {
+                    return false;
+                }
+                return getTableFilter().isEvaluatable();
+            }
             return evaluatable || visitor.getQueryLevel() < this.queryLevel;
         case ExpressionVisitor.SET_MAX_DATA_MODIFICATION_ID:
             visitor.addDataModificationId(column.getTable().getMaxDataModificationId());

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

@@ -11,6 +11,7 @@ import java.util.HashMap;
 import org.h2.engine.Session;
 import org.h2.expression.Expression;
 import org.h2.expression.ExpressionVisitor;
+import org.h2.table.TableFilter.TableFilterVisitor;
 import org.h2.util.New;
 
 /**
@@ -33,20 +34,21 @@ public class Plan {
     public Plan(TableFilter[] filters, int count, Expression condition) {
         this.filters = new TableFilter[count];
         System.arraycopy(filters, 0, this.filters, 0, count);
-        ArrayList<Expression> allCond = New.arrayList();
-        ArrayList<TableFilter> all = New.arrayList();
+        final ArrayList<Expression> allCond = New.arrayList();
+        final ArrayList<TableFilter> all = New.arrayList();
         if (condition != null) {
             allCond.add(condition);
         }
         for (int i = 0; i < count; i++) {
             TableFilter f = filters[i];
-            do {
-                all.add(f);
-                if (f.getJoinCondition() != null) {
-                    allCond.add(f.getJoinCondition());
+            f.visit(new TableFilterVisitor() {
+                public void accept(TableFilter f) {
+                    all.add(f);
+                    if (f.getJoinCondition() != null) {
+                        allCond.add(f.getJoinCondition());
+                    }
                 }
-                f = f.getJoin();
-            } while(f != null);
+            });
         }
         allConditions = new Expression[allCond.size()];
         allCond.toArray(allConditions);
@@ -126,6 +128,7 @@ public class Plan {
     }
 
     private void setEvaluatable(TableFilter filter, boolean b) {
+        filter.setEvaluatable(filter, b);
         for (Expression e : allConditions) {
             e.setEvaluatable(filter, b);
         }

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

@@ -38,9 +38,9 @@ public class RangeTable extends Table {
      * @param min the start expression
      * @param max the end expression
      */
-    public RangeTable(Schema schema, Expression min, Expression max) {
+    public RangeTable(Schema schema, Expression min, Expression max, boolean noColumns) {
         super(schema, 0, NAME, true, true);
-        Column[] cols = { new Column("X", Value.LONG) };
+        Column[] cols = noColumns ? new Column[0] : new Column[] { new Column("X", Value.LONG) };
         this.min = min;
         this.max = max;
         setColumns(cols);

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

@@ -40,6 +40,7 @@ public class TableFilter implements ColumnResolver {
     private Session session;
     private Index index;
     private int scanCount;
+    private boolean evaluatable;
 
     /**
      * Indicates that this filter is used in the plan.
@@ -70,22 +71,22 @@ public class TableFilter implements ColumnResolver {
     private SearchRow currentSearchRow;
     private Row current;
     private int state;
-    
+
     /**
      * The joined table (if there is one).
      */
     private TableFilter join;
-    
+
     /**
      * Whether this table is an outer join.
      */
     private boolean joinOuter;
-    
+
     /**
      * The nested joined table (if there is one).
      */
     private TableFilter nestedJoin;
-    
+
     private ArrayList<Column> naturalJoinColumns;
     private boolean foundOne;
     private Expression fullCondition;
@@ -186,6 +187,10 @@ public class TableFilter implements ColumnResolver {
     }
 
     private void setEvaluatable(TableFilter join) {
+        if (SysProperties.NESTED_JOINS) {
+            setEvaluatable(true);
+            return;
+        }
         // this table filter is now evaluatable - in all sub-joins
         do {
             Expression e = join.getJoinCondition();
@@ -306,25 +311,8 @@ public class TableFilter implements ColumnResolver {
         } else {
             // state == FOUND || NULL_ROW
             // the last row was ok - try next row of the join
-            if (nestedJoin != null) {
-                if (join == null) {
-                    if (nestedJoin.next()) {
-                        return true;
-                    }
-                } else {
-                    while (true) {
-                        if (nestedJoin.next()) {
-                            if (join.next()) {
-                                return true;
-                            }
-                            join.reset();
-                        }
-                    }
-                }
-            } else {
-                if (join != null && join.next()) {
-                    return true;
-                }
+            if (join != null && join.next()) {
+                return true;
             }
         }
         while (true) {
@@ -334,6 +322,10 @@ public class TableFilter implements ColumnResolver {
             }
             if (cursor.isAlwaysFalse()) {
                 state = AFTER_LAST;
+            } else if (nestedJoin != null) {
+                if (state == BEFORE_FIRST) {
+                    state = FOUND;
+                }
             } else {
                 if ((++scanCount & 4095) == 0) {
                     checkTimeout();
@@ -346,6 +338,16 @@ public class TableFilter implements ColumnResolver {
                     state = AFTER_LAST;
                 }
             }
+            if (nestedJoin != null && state == FOUND) {
+                if (!nestedJoin.next()) {
+                    state = AFTER_LAST;
+                    if (joinOuter && !foundOne) {
+                        // possibly null row
+                    } else {
+                        continue;
+                    }
+                }
+            }
             // if no more rows found, try the null row (for outer joins only)
             if (state == AFTER_LAST) {
                 if (joinOuter && !foundOne) {
@@ -354,12 +356,6 @@ public class TableFilter implements ColumnResolver {
                     break;
                 }
             }
-            if (state == FOUND && nestedJoin != null) {
-                nestedJoin.reset();
-                if (!nestedJoin.next()) {
-                    continue;
-                }
-            }
             if (!isOk(filterCondition)) {
                 continue;
             }
@@ -385,14 +381,17 @@ public class TableFilter implements ColumnResolver {
         state = AFTER_LAST;
         return false;
     }
-    
-    private void setNullRow() {
+
+    protected void setNullRow() {
         state = NULL_ROW;
         current = table.getNullRow();
         currentSearchRow = current;
         if (nestedJoin != null) {
-            int todoRecurse;
-            nestedJoin.setNullRow();
+            nestedJoin.visit(new TableFilterVisitor() {
+                public void accept(TableFilter f) {
+                    f.setNullRow();
+                }
+            });
         }
     }
 
@@ -484,9 +483,21 @@ public class TableFilter implements ColumnResolver {
      * @param outer if this is an outer join
      * @param on the join condition
      */
-    public void addJoin(TableFilter filter, boolean outer, boolean nested, Expression on) {
+    public void addJoin(TableFilter filter, boolean outer, boolean nested, final Expression on) {
         if (on != null) {
             on.mapColumns(this, 0);
+            if (SysProperties.NESTED_JOINS) {
+                visit(new TableFilterVisitor() {
+                    public void accept(TableFilter f) {
+                        on.mapColumns(f, 0);
+                    }
+                });
+                filter.visit(new TableFilterVisitor() {
+                    public void accept(TableFilter f) {
+                        on.mapColumns(f, 0);
+                    }
+                });
+            }
         }
         if (nested && SysProperties.NESTED_JOINS) {
             if (nestedJoin != null) {
@@ -529,9 +540,6 @@ public class TableFilter implements ColumnResolver {
         on.mapColumns(this, 0);
         addFilterCondition(on, true);
         on.createIndexConditions(session, this);
-        if (nestedJoin != null) {
-            nestedJoin.mapAndAddFilter(on);
-        }
         if (join != null) {
             join.mapAndAddFilter(on);
         }
@@ -566,7 +574,22 @@ public class TableFilter implements ColumnResolver {
             }
         }
         if (nestedJoin != null) {
-            buff.append("(");
+            buff.append("(\n");
+            TableFilter n = nestedJoin;
+            do {
+                buff.append(n.getPlanSQL(n != nestedJoin));
+                buff.append("\n");
+                n = (TableFilter) n.getJoin();
+            } while (n != null);
+            buff.append(") ON ");
+            if (joinCondition == null) {
+                // need to have a ON expression, 
+                // otherwise the nesting is unclear
+                buff.append("1=1");
+            } else {
+                buff.append(StringUtils.unEnclose(joinCondition.getSQL()));
+            }
+            return buff.toString();
         }
         buff.append(table.getSQL());
         if (alias != null) {
@@ -586,11 +609,6 @@ public class TableFilter implements ColumnResolver {
             String plan = StringUtils.quoteRemarkSQL(planBuff.toString());
             buff.append(plan).append(" */");
         }
-        if (nestedJoin != null) {
-            buff.append('\n');
-            buff.append(nestedJoin.getPlanSQL(true));
-            buff.append(")");
-        }
         if (isJoin) {
             buff.append(" ON ");
             if (joinCondition == null) {
@@ -713,6 +731,7 @@ public class TableFilter implements ColumnResolver {
      * @param b the new flag
      */
     public void setEvaluatable(TableFilter filter, boolean b) {
+        setEvaluatable(b);
         if (filterCondition != null) {
             filterCondition.setEvaluatable(filter, b);
         }
@@ -727,6 +746,10 @@ public class TableFilter implements ColumnResolver {
         }
     }
 
+    public void setEvaluatable(boolean evaluatable) {
+        this.evaluatable = evaluatable;
+    }
+
     public String getSchemaName() {
         return table.getSchema().getName();
     }
@@ -855,4 +878,24 @@ public class TableFilter implements ColumnResolver {
         return nestedJoin;
     }
 
+    public void visit(TableFilterVisitor visitor) {
+        TableFilter f = this;
+        do {
+            visitor.accept(f);
+            TableFilter n = f.nestedJoin;
+            if (n != null) {
+                n.visit(visitor);
+            }
+            f = (TableFilter) f.join;
+        } while (f != null);
+    }
+
+    public static interface TableFilterVisitor {
+        public void accept(TableFilter f);
+    }
+
+    public boolean isEvaluatable() {
+        return evaluatable;
+    }
+
 }