| /* |
| |
| Derby - Class org.apache.derby.impl.sql.compile.RowCountNode |
| |
| Licensed to the Apache Software Foundation (ASF) under one or more |
| contributor license agreements. See the NOTICE file distributed with |
| this work for additional information regarding copyright ownership. |
| The ASF licenses this file to you under the Apache License, Version 2.0 |
| (the "License"); you may not use this file except in compliance with |
| the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| |
| */ |
| |
| package org.apache.derby.impl.sql.compile; |
| |
| import org.apache.derby.iapi.error.StandardException; |
| import org.apache.derby.iapi.services.compiler.MethodBuilder; |
| import org.apache.derby.shared.common.sanity.SanityManager; |
| import org.apache.derby.iapi.services.classfile.VMOpcode; |
| import org.apache.derby.iapi.reference.ClassName; |
| import org.apache.derby.iapi.services.context.ContextManager; |
| |
| /** |
| * The result set generated by this node (RowCountResultSet) implements the |
| * filtering of rows needed for the <result offset clause> and the <fetch first |
| * clause>. It sits on top of the normal SELECT's top result set, but under any |
| * ScrollInsensitiveResultSet. The latter's positioning is needed for the correct |
| * functioning of <result offset clause> and <fetch first clause> in the |
| * presence of scrollable and/or updatable result sets and CURRENT OF cursors. |
| */ |
| public final class RowCountNode extends SingleChildResultSetNode |
| { |
| /** |
| * If not null, this represents the value of a <result offset clause>. |
| */ |
| private ValueNode offset; |
| /** |
| * If not null, this represents the value of a <fetch first clause>. |
| */ |
| private ValueNode fetchFirst; |
| /** |
| * True if the offset/fetchFirst clauses were added by JDBC LIMIT syntax. |
| */ |
| private boolean hasJDBClimitClause; |
| |
| |
| /** |
| * Constructor for a RowCountNode |
| * |
| * @exception StandardException |
| */ |
| |
| /** |
| * Constructor for a RowCountNode |
| * @param childResult The result set for which we want to get |
| * only a subset |
| * @param rcl The result columns we want |
| * @param offset The offset, if any, in the result set |
| * @param fetchFirst The number of rows to inspect to get |
| * @param hasJDBClimitClause {@code true} if a JDBC limit syntax was used |
| * @param cm The context manager |
| * @throws StandardException |
| */ |
| RowCountNode(ResultSetNode childResult, |
| ResultColumnList rcl, |
| ValueNode offset, |
| ValueNode fetchFirst, |
| boolean hasJDBClimitClause, |
| ContextManager cm) |
| throws StandardException { |
| |
| super(childResult, null, cm); |
| setResultColumns( rcl ); |
| |
| this.offset = offset; |
| this.fetchFirst = fetchFirst; |
| this.hasJDBClimitClause = hasJDBClimitClause; |
| } |
| |
| |
| /** |
| * Generate code. |
| * |
| * @param acb activation class builder |
| * @param mb method builder |
| * |
| * @exception StandardException Thrown on error |
| */ |
| @Override |
| void generate(ActivationClassBuilder acb, MethodBuilder mb) |
| throws StandardException { |
| |
| /* Get the next ResultSet #, so that we can number this ResultSetNode, |
| * its ResultColumnList and ResultSet. |
| */ |
| assignResultSetNumber(); |
| |
| setCostEstimate( childResult.getFinalCostEstimate() ); |
| |
| acb.pushGetResultSetFactoryExpression(mb); |
| |
| childResult.generate(acb, mb); // arg1 |
| |
| acb.pushThisAsActivation(mb); // arg2 |
| mb.push(getResultSetNumber()); // arg3 |
| |
| boolean dynamicOffset = false; |
| boolean dynamicFetchFirst = false; |
| |
| // arg4 |
| if (offset != null) { |
| generateExprFun(acb, mb, offset); |
| } else { |
| mb.pushNull(ClassName.GeneratedMethod); |
| } |
| |
| // arg5 |
| if (fetchFirst != null) { |
| generateExprFun(acb, mb, fetchFirst); |
| } else { |
| mb.pushNull(ClassName.GeneratedMethod); |
| } |
| |
| mb.push( hasJDBClimitClause ); // arg6 |
| |
| mb.push(getCostEstimate().rowCount()); // arg7 |
| mb.push(getCostEstimate().getEstimatedCost()); // arg8 |
| |
| mb.callMethod(VMOpcode.INVOKEINTERFACE, |
| (String) null, |
| "getRowCountResultSet", |
| ClassName.NoPutResultSet, |
| 8); |
| } |
| |
| |
| private void generateExprFun( |
| ExpressionClassBuilder ecb, |
| MethodBuilder mb, |
| ValueNode vn) throws StandardException { |
| |
| // Generates: |
| // Object exprFun { } |
| MethodBuilder exprFun = ecb.newExprFun(); |
| |
| /* generates: |
| * return <dynamic parameter.generate(ecb)>; |
| * and adds it to exprFun |
| */ |
| vn.generateExpression(ecb, exprFun); |
| exprFun.methodReturn(); |
| |
| // we are done modifying exprFun, complete it. |
| exprFun.complete(); |
| |
| // Pass in the method that will be used to evaluates the dynamic |
| // parameter in RowCountResultSet. |
| ecb.pushMethodReference(mb, exprFun); |
| } |
| |
| |
| /** |
| * Convert this object to a String. See comments in QueryTreeNode.java |
| * for how this should be done for tree printing. |
| * |
| * @return This object as a String |
| */ |
| @Override |
| public String toString() { |
| if (SanityManager.DEBUG) { |
| return "offset: " + offset + "\n" + |
| "fetchFirst:" + fetchFirst + "\n" + |
| super.toString(); |
| } else { |
| return ""; |
| } |
| } |
| } |