/*
Derby - Class org.apache.derby.impl.sql.compile.SelectNode
Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable.
Licensed 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.sql.compile.Optimizer;
import org.apache.derby.iapi.sql.compile.Visitable;
import org.apache.derby.iapi.sql.compile.Visitor;
import org.apache.derby.iapi.sql.compile.C_NodeTypes;
import org.apache.derby.iapi.sql.dictionary.DataDictionary;
import org.apache.derby.iapi.sql.dictionary.TableDescriptor;
import org.apache.derby.iapi.types.TypeId;
import org.apache.derby.iapi.types.DataTypeDescriptor;
import org.apache.derby.iapi.reference.DB2Limit;
import org.apache.derby.iapi.reference.SQLState;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.store.access.TransactionController;
import org.apache.derby.iapi.services.sanity.SanityManager;
import org.apache.derby.iapi.util.JBitSet;
import java.util.Vector;
/**
* A SelectNode represents the result set for any of the basic DML
* operations: SELECT, INSERT, UPDATE, and DELETE. (A RowResultSetNode
* will be used for an INSERT with a VALUES clause.) For INSERT - SELECT,
* any of the fields in a SelectNode can be used (the SelectNode represents
* the SELECT statement in the INSERT - SELECT). For UPDATE and
* DELETE, there will be one table in the fromList, and the groupByList
* fields will be null. For both INSERT and UPDATE,
* the resultColumns in the selectList will contain the names of the columns
* being inserted into or updated.
*
* @author Jeff Lichtman
*/
public class SelectNode extends ResultSetNode
{
/**
* List of tables in the FROM clause of this SELECT
*/
FromList fromList;
FromTable targetTable;
/* Aggregate Vectors for select and where clauses */
Vector selectAggregates ;
Vector whereAggregates;
/**
* The ValueNode for the WHERE clause must represent a boolean
* expression. The binding phase will enforce this - the parser
* does not have enough information to enforce it in all cases
* (for example, user methods that return boolean).
*/
ValueNode whereClause;
ValueNode originalWhereClause;
/**
* List of result columns in GROUP BY clause
*/
GroupByList groupByList;
/* List of columns in ORDER BY list */
OrderByList orderByList;
boolean orderByQuery ;
/* PredicateLists for where clause */
PredicateList wherePredicates;
/* SubqueryLists for select and where clauses */
SubqueryList selectSubquerys;
SubqueryList whereSubquerys;
/* Whether or not we are only binding the target list */
private boolean bindTargetListOnly;
private boolean isDistinct;
private boolean orderByAndDistinctMerged;
private boolean generatedForGroupByClause;
private boolean generatedForHavingClause;
/* Copy of fromList prior to generating join tree */
private FromList preJoinFL;
/**
* Initializer for a SelectNode.
*
* @param selectList The result column list for the SELECT statement
* @param aggregateVector The aggregate vector for this SELECT
* @param fromList The FROM list for the SELECT statement
* @param whereClause An expression representing the WHERE clause.
* It must be a boolean expression, but this is
* not checked until binding.
* @param groupByList The GROUP BY list, if any.
* @exception StandardException Thrown on error
*/
public void init(Object selectList,
Object aggregateVector,
Object fromList,
Object whereClause,
Object groupByList)
throws StandardException
{
/* RESOLVE - remove aggregateList from constructor.
* Consider adding selectAggregates and whereAggregates
*/
resultColumns = (ResultColumnList) selectList;
this.fromList = (FromList) fromList;
this.whereClause = (ValueNode) whereClause;
this.originalWhereClause = (ValueNode) whereClause;
this.groupByList = (GroupByList) groupByList;
bindTargetListOnly = false;
}
/**
* 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
*/
public String toString()
{
if (SanityManager.DEBUG)
{
return "isDistinct: "+ isDistinct + "\n"+
"groupByList: " +
(groupByList != null ? groupByList.toString() : "null") + "\n" +
"orderByList: " +
(orderByList != null ? orderByList.toString() : "null") + "\n" +
"generatedForGroupByClause: " +generatedForGroupByClause +"\n" +
"generatedForHavingClause: " + generatedForHavingClause + "\n" +
super.toString();
}
else
{
return "";
}
}
public String statementToString()
{
return "SELECT";
}
public void makeDistinct()
{
isDistinct = true;
}
public void clearDistinct()
{
isDistinct = false;
}
boolean hasDistinct()
{
return isDistinct;
}
/**
* Mark this SelectNode as being generated for a GROUP BY clause.
*
* @return Nothing.
*/
public void markAsForGroupByClause()
{
generatedForGroupByClause = true;
}
/**
* Return whether or not this SelectNode was generated for a GROUP BY clause.
*
* @return boolean Whether or not this SelectNode was generated for a GROUP BY clause.
*/
public boolean getGeneratedForGroupbyClause()
{
return generatedForGroupByClause;
}
/**
* Mark this SelectNode as being generated for a HAVING clause.
*
* @return Nothing.
*/
public void markAsForHavingClause()
{
generatedForHavingClause = true;
}
/**
* Prints the sub-nodes of this object. See QueryTreeNode.java for
* how tree printing is supposed to work.
*
* @param depth The depth of this node in the tree
*
* @return Nothing
*/
public void printSubNodes(int depth)
{
if (SanityManager.DEBUG)
{
super.printSubNodes(depth);
if (selectSubquerys != null)
{
printLabel(depth, "selectSubquerys: ");
selectSubquerys.treePrint(depth + 1);
}
printLabel(depth, "fromList: ");
if (fromList != null)
{
fromList.treePrint(depth + 1);
}
if (whereClause != null)
{
printLabel(depth, "whereClause: ");
whereClause.treePrint(depth + 1);
}
if ((wherePredicates != null) &&wherePredicates.size() > 0)
{
printLabel(depth, "wherePredicates: ");
wherePredicates.treePrint(depth + 1);
}
if (whereSubquerys != null)
{
printLabel(depth, "whereSubquerys: ");
whereSubquerys.treePrint(depth + 1);
}
printLabel(depth, "preJoinFL: ");
if (preJoinFL != null)
{
preJoinFL.treePrint(depth + 1);
}
}
}
/**
* Return the fromList for this SelectNode.
*
* @return FromList The fromList for this SelectNode.
*/
public FromList getFromList()
{
return fromList;
}
/**
* Return the groupByList for this SelectNode.
*
* @return GroupByList The groupByList for this SelectNode.
*/
public GroupByList getGroupByList()
{
return groupByList;
}
/**
* Return the whereClause for this SelectNode.
*
* @return ValueNode The whereClause for this SelectNode.
*/
public ValueNode getWhereClause()
{
return whereClause;
}
/**
* Return the wherePredicates for this SelectNode.
*
* @return PredicateList The wherePredicates for this SelectNode.
*/
public PredicateList getWherePredicates()
{
return wherePredicates;
}
/**
* Return the selectSubquerys for this SelectNode.
*
* @return SubqueryList The selectSubquerys for this SelectNode.
*/
public SubqueryList getSelectSubquerys()
{
return selectSubquerys;
}
/**
* Return the specified aggregate vector for this SelectNode.
*
* @param clause Which clause to get the aggregate list for
*
* @return aggregateVector The specified aggregate vector for this SelectNode.
*/
public Vector getAggregateVector(int clause)
{
switch (clause)
{
case ValueNode.IN_SELECT_LIST:
return selectAggregates;
case ValueNode.IN_WHERE_CLAUSE:
if (generatedForHavingClause)
{
return null;
}
else
{
return whereAggregates;
}
case ValueNode.IN_HAVING_CLAUSE:
if (generatedForHavingClause)
{
return whereAggregates;
}
else
{
return null;
}
default:
if (SanityManager.DEBUG)
{
SanityManager.ASSERT(false,
"Unexpected value for clause");
}
return null;
}
}
/**
* Return the whereSubquerys for this SelectNode.
*
* @return SubqueryList The whereSubquerys for this SelectNode.
*/
public SubqueryList getWhereSubquerys()
{
return whereSubquerys;
}
/**
* Bind the tables in this SelectNode. This includes getting their
* TableDescriptors from the DataDictionary and numbering the FromTables.
* NOTE: Because this node represents the top of a new query block, we bind
* both the non VTI and VTI tables under this node in this method call.
*
* @param dataDictionary The DataDictionary to use for binding
* @param fromListParam FromList to use/append to.
*
* @return ResultSetNode
*
* @exception StandardException Thrown on error
*/
public ResultSetNode bindNonVTITables(DataDictionary dataDictionary,
FromList fromListParam)
throws StandardException
{
int fromListParamSize = fromListParam.size();
int fromListSize = fromList.size();
int nestingLevel;
FromList fromListClone = (FromList) getNodeFactory().getNode(
C_NodeTypes.FROM_LIST,
getNodeFactory().doJoinOrderOptimization(),
getContextManager());
wherePredicates = (PredicateList) getNodeFactory().getNode(
C_NodeTypes.PREDICATE_LIST,
getContextManager());
preJoinFL = (FromList) getNodeFactory().getNode(
C_NodeTypes.FROM_LIST,
getNodeFactory().doJoinOrderOptimization(),
getContextManager());
/* Set the nesting level in the fromList */
if (fromListParam.size() == 0)
{
nestingLevel = 0;
}
else
{
nestingLevel = ((FromTable) fromListParam.elementAt(0)).getLevel() + 1;
}
fromList.setLevel(nestingLevel);
/* Splice a clone of our FromList on to the beginning of fromListParam, before binding
* the tables, for correlated column resolution in VTIs.
*/
for (int index = 0; index < fromListSize; index++)
{
fromListParam.insertElementAt(fromList.elementAt(index), 0);
}
// Now bind our from list
fromList.bindTables(dataDictionary, fromListParam);
/* Restore fromListParam */
for (int index = 0; index < fromListSize; index++)
{
fromListParam.removeElementAt(0);
}
return this;
}
/**
* Bind the expressions in this SelectNode. This means binding the
* sub-expressions, as well as figuring out what the return type is
* for each expression.
*
* @param fromListParam FromList to use/append to.
*
* @return Nothing
*
* @exception StandardException Thrown on error
*/
public void bindExpressions(FromList fromListParam)
throws StandardException
{
int fromListParamSize = fromListParam.size();
int fromListSize = fromList.size();
int numDistinctAggs;
if (SanityManager.DEBUG)
SanityManager.ASSERT(fromList != null && resultColumns != null,
"Both fromList and resultColumns are expected to be non-null");
/* NOTE - a lot of this code would be common to bindTargetExpression(),
* so we use a private boolean to share the code instead of duplicating
* it. bindTargetExpression() is responsible for toggling the boolean.
*/
if (! bindTargetListOnly)
{
/* Bind the expressions in FromSubquerys, JoinNodes, etc. */
fromList.bindExpressions();
}
selectSubquerys = (SubqueryList) getNodeFactory().getNode(
C_NodeTypes.SUBQUERY_LIST,
getContextManager());
selectAggregates = new Vector();
/* Splice our FromList on to the beginning of fromListParam, before binding
* the expressions, for correlated column resolution.
*/
for (int index = 0; index < fromListSize; index++)
{
fromListParam.insertElementAt(fromList.elementAt(index), index);
}
resultColumns.setClause(ValueNode.IN_SELECT_LIST);
resultColumns.bindExpressions(fromListParam,
selectSubquerys,
selectAggregates);
/* We're done if we're only binding the target list.
* (After we restore the fromList, of course.)
*/
if (bindTargetListOnly)
{
for (int index = 0; index < fromListSize; index++)
{
fromListParam.removeElementAt(0);
}
return;
}
whereAggregates = new Vector();
whereSubquerys = (SubqueryList) getNodeFactory().getNode(
C_NodeTypes.SUBQUERY_LIST,
getContextManager());
if (whereClause != null)
{
whereClause = whereClause.bindExpression(fromListParam,
whereSubquerys,
whereAggregates);
/* RESOLVE - Temporarily disable aggregates in the HAVING clause.
** (We may remove them in the parser anyway.)
** RESOLVE - Disable aggregates in the WHERE clause. Someday
** Aggregates will be allowed iff they are in a subquery
** of the having clause and they correlate to an outer
** query block. For now, aggregates are not supported
** in the WHERE clause at all.
** Note: a similar check is made in JoinNode.
*/
if ((whereAggregates.size() > 0) &&
!generatedForHavingClause)
{
throw StandardException.newException(SQLState.LANG_NO_AGGREGATES_IN_WHERE_CLAUSE);
}
/* If whereClause is a parameter, (where ?), then we should catch it and throw exception
*/
if (whereClause.isParameterNode())
{
throw StandardException.newException(SQLState.LANG_NON_BOOLEAN_WHERE_CLAUSE, "PARAMETER" );
}
whereClause = whereClause.checkIsBoolean();
}
/* Restore fromList */
for (int index = 0; index < fromListSize; index++)
{
fromListParam.removeElementAt(0);
}
if (SanityManager.DEBUG) {
SanityManager.ASSERT(fromListParam.size() == fromListParamSize,
"fromListParam.size() = " + fromListParam.size() +
", expected to be restored to " + fromListParamSize);
SanityManager.ASSERT(fromList.size() == fromListSize,
"fromList.size() = " + fromList.size() +
", expected to be restored to " + fromListSize);
}
/* If query is grouped, bind the group by list. */
if (groupByList != null)
{
Vector gbAggregateVector = new Vector();
groupByList.bindGroupByColumns(this,
gbAggregateVector);
/*
** There should be no aggregates in the Group By list.
** We don't expect any, but just to be on the safe side
** we will check under sanity.
*/
if (SanityManager.DEBUG)
{
SanityManager.ASSERT(gbAggregateVector.size() == 0,
"Unexpected Aggregate vector generated by Group By clause");
}
}
/* If ungrouped query with aggregates in SELECT list, verify
* that all result columns are valid aggregate expressions -
* no column references outside of an aggregate.
* If grouped query with aggregates in SELECT list, verify that all
* result columns are either grouping columns or valid
* grouped aggregate expressions - the only column references allowed
* outside of an aggregage are columns in the group by list.
*/
if (groupByList != null || selectAggregates.size() > 0)
{
VerifyAggregateExpressionsVisitor visitor =
new VerifyAggregateExpressionsVisitor(groupByList);
resultColumns.accept(visitor);
}
/*
** RESOLVE: for now, only one distinct aggregate is supported
** in the select list.
*/
numDistinctAggs = numDistinctAggregates(selectAggregates);
if (numDistinctAggs > 1)
{
throw StandardException.newException(SQLState.LANG_USER_AGGREGATE_MULTIPLE_DISTINCTS);
}
}
/**
* Bind the expressions in this ResultSetNode if it has tables. This means binding the
* sub-expressions, as well as figuring out what the return type is for
* each expression.
*
* @param fromListParam FromList to use/append to.
*
* @return Nothing
*
* @exception StandardException Thrown on error
*/
public void bindExpressionsWithTables(FromList fromListParam)
throws StandardException
{
/* We have tables, so simply call bindExpressions() */
bindExpressions(fromListParam);
}
/**
* Bind the expressions in the target list. This means binding the
* sub-expressions, as well as figuring out what the return type is
* for each expression. This is useful for EXISTS subqueries, where we
* need to validate the target list before blowing it away and replacing
* it with a SELECT true.
*
* @return Nothing
*
* @exception StandardException Thrown on error
*/
public void bindTargetExpressions(FromList fromListParam)
throws StandardException
{
bindTargetListOnly = true;
bindExpressions(fromListParam);
bindTargetListOnly = false;
}
/**
* Bind the result columns of this ResultSetNode when there is no
* base table to bind them to. This is useful for SELECT statements,
* where the result columns get their types from the expressions that
* live under them.
*
* @param fromListParam FromList to use/append to.
*
* @return Nothing
*
* @exception StandardException Thrown on error
*/
public void bindResultColumns(FromList fromListParam)
throws StandardException
{
/* We first bind the resultColumns for any FromTable which
* needs its own binding, such as JoinNodes.
* We pass through the fromListParam without adding our fromList
* to it, since the elements in our fromList can only be correlated
* with outer query blocks.
*/
fromList.bindResultColumns(fromListParam);
super.bindResultColumns(fromListParam);
/* Only 1012 elements allowed in select list */
if (resultColumns.size() > DB2Limit.DB2_MAX_ELEMENTS_IN_SELECT_LIST)
{
throw StandardException.newException(SQLState.LANG_TOO_MANY_ELEMENTS);
}
/* Fix nullability in case of any outer joins in the fromList */
if (fromList.hasOuterJoins())
resultColumns.setNullability(true);
}
/**
* Bind the result columns for this ResultSetNode to a base table.
* This is useful for INSERT and UPDATE statements, where the
* result columns get their types from the table being updated or
* inserted into.
* If a result column list is specified, then the verification that the
* result column list does not contain any duplicates will be done when
* binding them by name.
*
* @param targetTableDescriptor The TableDescriptor for the table being
* updated or inserted into
* @param targetColumnList For INSERT statements, the user
* does not have to supply column
* names (for example, "insert into t
* values (1,2,3)". When this
* parameter is null, it means that
* the user did not supply column
* names, and so the binding should
* be done based on order. When it
* is not null, it means do the binding
* by name, not position.
* @param statement Calling DMLStatementNode (Insert or Update)
* @param fromListParam FromList to use/append to.
*
* @return Nothing
*
* @exception StandardException Thrown on error
*/
public void bindResultColumns(TableDescriptor targetTableDescriptor,
FromVTI targetVTI,
ResultColumnList targetColumnList,
DMLStatementNode statement,
FromList fromListParam)
throws StandardException
{
/* We first bind the resultColumns for any FromTable which
* needs its own binding, such as JoinNodes.
* We pass through the fromListParam without adding our fromList
* to it, since the elements in our fromList can only be correlated
* with outer query blocks.
*/
fromList.bindResultColumns(fromListParam);
super.bindResultColumns(targetTableDescriptor,
targetVTI,
targetColumnList, statement,
fromListParam);
}
/**
* Push an expression into this SELECT (and possibly down into
* one of the tables in the FROM list). This is useful when
* trying to push predicates into unflattened views or
* derived tables.
*
* @param predicate The predicate that we attempt to push
*
* @return None
*
* @exception StandardException Thrown on error
*/
void pushExpressionsIntoSelect(Predicate predicate)
throws StandardException
{
wherePredicates.pullExpressions(referencedTableMap.size(), predicate.getAndNode());
fromList.pushPredicates(wherePredicates);
}
/**
* Verify that a SELECT * is valid for this type of subquery.
*
* @param outerFromList The FromList from the outer query block(s)
* @param subqueryType The subquery type
*
* @return None
*
* @exception StandardException Thrown on error
*/
public void verifySelectStarSubquery(FromList outerFromList, int subqueryType)
throws StandardException
{
if (! ((ResultColumn) resultColumns.elementAt(0) instanceof AllResultColumn) )
{
return;
}
/* Select * always okay when SelectNode generated to wrap
* GROUP BY or HAVING.
*/
if (generatedForGroupByClause || generatedForHavingClause)
{
return;
}
/* Select * currently only valid for EXISTS/NOT EXISTS.
* NOT EXISTS does not appear prior to preprocessing.
*/
if (subqueryType != SubqueryNode.EXISTS_SUBQUERY)
{
throw StandardException.newException(SQLState.LANG_CANT_SELECT_STAR_SUBQUERY);
}
/* If the AllResultColumn is qualified, then we have to verify
* that the qualification is a valid exposed name.
* NOTE: The exposed name can come from an outer query block.
*/
String fullTableName;
fullTableName = ((AllResultColumn) resultColumns.elementAt(0)).getFullTableName();
if (fullTableName != null)
{
if (fromList.getFromTableByName(fullTableName, null, true) == null &&
outerFromList.getFromTableByName(fullTableName, null, true) == null)
{
if (fromList.getFromTableByName(fullTableName, null, false) == null &&
outerFromList.getFromTableByName(fullTableName, null, false) == null)
{
throw StandardException.newException(SQLState.LANG_EXPOSED_NAME_NOT_FOUND, fullTableName);
}
}
}
}
/**
* Determine whether or not the specified name is an exposed name in
* the current query block.
*
* @param name The specified name to search for as an exposed name.
* @param schemaName Schema name, if non-null.
* @param exactMatch Whether or not we need an exact match on specified schema and table
* names or match on table id.
*
* @return The FromTable, if any, with the exposed name.
*
* @exception StandardException Thrown on error
*/
protected FromTable getFromTableByName(String name, String schemaName, boolean exactMatch)
throws StandardException
{
return fromList.getFromTableByName(name, schemaName, exactMatch);
}
/**
* Check for (and reject) ? parameters directly under the ResultColumns.
* This is done for SELECT statements.
*
* @return Nothing
*
* @exception StandardException Thrown if a ? parameter found
* directly under a ResultColumn
*/
public void rejectParameters() throws StandardException
{
super.rejectParameters();
fromList.rejectParameters();
}
/**
* Push the order by list down from the cursor node
* into its child result set so that the optimizer
* has all of the information that it needs to
* consider sort avoidance.
*
* @param orderByList The order by list
*
* @return Nothing.
*/
void pushOrderByList(OrderByList orderByList)
{
this.orderByList = orderByList;
// remember that there was an order by list
orderByQuery = true;
}
/**
* Put a ProjectRestrictNode on top of each FromTable in the FromList.
* ColumnReferences must continue to point to the same ResultColumn, so
* that ResultColumn must percolate up to the new PRN. However,
* that ResultColumn will point to a new expression, a VirtualColumnNode,
* which points to the FromTable and the ResultColumn that is the source for
* the ColumnReference.
* (The new PRN will have the original of the ResultColumnList and
* the ResultColumns from that list. The FromTable will get shallow copies
* of the ResultColumnList and its ResultColumns. ResultColumn.expression
* will remain at the FromTable, with the PRN getting a new
* VirtualColumnNode for each ResultColumn.expression.)
* We then project out the non-referenced columns. If there are no referenced
* columns, then the PRN's ResultColumnList will consist of a single ResultColumn
* whose expression is 1.
*
* @param numTables The number of tables in the DML Statement
* @param gbl The outer group by list, if any
* @param fl The from list, if any
*
* @return The generated ProjectRestrictNode atop the original FromTable.
*
* @exception StandardException Thrown on error
*/
public ResultSetNode preprocess(int numTables,
GroupByList gbl,
FromList fl)
throws StandardException
{
ResultSetNode newTop = this;
/* Put the expression trees in conjunctive normal form.
* NOTE - This needs to occur before we preprocess the subqueries
* because the subquery transformations assume that any subquery operator
* negation has already occurred.
*/
normExpressions();
/**
* This method determines if (1) the query is a LOJ, and (2) if the LOJ is a candidate for
* reordering (i.e., linearization). The condition for LOJ linearization is:
* 1. either LOJ or ROJ in the fromList, i.e., no INNER, NO FULL JOINs
* 2. ON clause must be equality join between left and right operands and in CNF (i.e., AND is allowed)
*/
boolean anyChange = fromList.LOJ_reorderable(numTables);
if (anyChange)
{
FromList afromList = (FromList) getNodeFactory().getNode(C_NodeTypes.FROM_LIST,
getNodeFactory().doJoinOrderOptimization(),
getContextManager());
bindExpressions(afromList);
}
/* Preprocess the fromList. For each FromTable, if it is a FromSubquery
* then we will preprocess it, replacing the FromSubquery with a
* ProjectRestrictNode. If it is a FromBaseTable, then we will generate
* the ProjectRestrictNode above it.
*/
fromList.preprocess(numTables, groupByList, whereClause);
/* selectSubquerys is always allocated at bind() time */
if (SanityManager.DEBUG)
{
SanityManager.ASSERT(selectSubquerys != null,
"selectSubquerys is expected to be non-null");
}
/* Preprocess the RCL after the from list so that
* we can flatten/optimize any subqueries in the
* select list.
*/
resultColumns.preprocess(numTables,
fromList, whereSubquerys,
wherePredicates);
/* Preprocess the expressions. (This is necessary for subqueries.
* This is also where we do tranformations such as for LIKE.)
*
* NOTE: We do this after preprocessing the fromList so that, for
* quantified subqueries, the join expression with the outer
* expression will be pushable (to be pushable, the ColumnReference
* has to point to a VirtualColumnNode, and not to a BaseColumnNode).
*/
if (whereClause != null)
{
whereClause.preprocess(numTables,
fromList, whereSubquerys,
wherePredicates);
}
/* Pull apart the expression trees */
if (whereClause != null)
{
wherePredicates.pullExpressions(numTables, whereClause);
whereClause = null;
}
/* RESOLVE - Where should we worry about expression pull up for
* expensive predicates?
*/
// Flatten any flattenable FromSubquerys or JoinNodes
fromList.flattenFromTables(resultColumns,
wherePredicates,
whereSubquerys,
groupByList);
if (wherePredicates != null && wherePredicates.size() > 0 && fromList.size() > 0)
{
// Perform various forms of transitive closure on wherePredicates
if (fromList.size() > 1)
{
performTransitiveClosure(numTables);
}
if (orderByList != null)
{
// Remove constant columns from order by list. Constant
// columns are ones that have equality comparisons with
// constant expressions (e.g. x = 3)
orderByList.removeConstantColumns(wherePredicates);
/*
** It's possible for the order by list to shrink to nothing
** as a result of removing constant columns. If this happens,
** get rid of the list entirely.
*/
if (orderByList.size() == 0)
{
orderByList = null;
}
}
}
/* A valid group by without any aggregates is equivalent to
* a distinct without the group by. We do the transformation
* in order to simplify the group by code.
*/
if (groupByList != null &&
selectAggregates.size() == 0 &&
whereAggregates.size() == 0)
{
isDistinct = true;
groupByList = null;
}
/* Consider distinct elimination based on a uniqueness condition.
* In order to do this:
* o All top level ColumnReferences in the select list are
* from the same base table. (select t1.c1, t2.c2 + t3.c3 is
* okay - t1 is the table of interest.)
* o If the from list is a single table then the columns in the
* select list plus the columns in the where clause that are
* in = comparisons with constants or parameters must be a
* superset of any unique index.
* o If the from list has multiple tables then at least 1 table
* meet the following - the set of columns in = comparisons
* with constants or parameters is a superset of any unique
* index on the table. All of the other tables must meet
* the following - the set of columns in = comparisons with
* constants, parameters or join columns is a superset of
* any unique index on the table. If the table from which
* the columns in the select list are coming from is in this
* later group then the rule for it is to also include
* the columns in the select list in the set of columns that
* needs to be a superset of the unique index. Whew!
*/
if (isDistinct && groupByList == null)
{
int distinctTable = resultColumns.allTopCRsFromSameTable();
if (distinctTable != -1)
{
if (fromList.returnsAtMostSingleRow(resultColumns,
whereClause, wherePredicates,
getDataDictionary()))
{
isDistinct = false;
}
}
/* If we were unable to eliminate the distinct and we have
* an order by then we can consider eliminating the sort for the
* order by. All of the columns in the order by list must
* be ascending in order to do this. There are 2 cases:
* o The order by list is an in order prefix of the columns
* in the select list. In this case the output of the
* sort from the distinct will be in the right order
* so we simply eliminate the order by list.
* o The order by list is a subset of the columns in the
* the select list. In this case we need to reorder the
* columns in the select list so that the ordering columns
* are an in order prefix of the select list and put a PRN
* above the select so that the shape of the result set
* is as expected.
*/
if (isDistinct && orderByList != null && orderByList.allAscending())
{
/* Order by list currently restricted to columns in select
* list, so we will always eliminate the order by here.
*/
if (orderByList.isInOrderPrefix(resultColumns))
{
orderByList = null;
}
else
{
/* Order by list is not an in order prefix of the select list
* so we must reorder the columns in the the select list to
* match the order by list and generate the PRN above us to
* preserve the expected order.
*/
newTop = genProjectRestrictForReordering();
orderByList.resetToSourceRCs();
resultColumns = orderByList.reorderRCL(resultColumns);
orderByList = null;
}
orderByAndDistinctMerged = true;
}
}
/*
* Push predicates that are pushable.
*
* NOTE: We pass the wherePredicates down to the new PRNs here,
* so they can pull any clauses and possibily push them down further.
* NOTE: We wait until all of the FromTables have been preprocessed
* until we attempt to push down predicates, because we cannot push down
* a predicate if the immediate source of any of its column references
* is not a ColumnReference or a VirtualColumnNode.
*/
fromList.pushPredicates(wherePredicates);
/* Set up the referenced table map */
referencedTableMap = new JBitSet(numTables);
int flSize = fromList.size();
for (int index = 0; index < flSize; index++)
{
referencedTableMap.or(((FromTable) fromList.elementAt(index)).
getReferencedTableMap());
}
/* Copy the referenced table map to the new tree top, if necessary */
if (newTop != this)
{
newTop.setReferencedTableMap((JBitSet) referencedTableMap.clone());
}
return newTop;
}
/**
* Peform the various types of transitive closure on the where clause.
* The 2 types are transitive closure on join clauses and on search clauses.
* Join clauses will be processed first to maximize benefit for search clauses.
*
* @param numTables The number of tables in the query
*
* @return None.
*
* @exception StandardException Thrown on error
*/
private void performTransitiveClosure(int numTables)
throws StandardException
{
// Join clauses
wherePredicates.joinClauseTransitiveClosure(numTables, fromList, getCompilerContext());
// Search clauses
wherePredicates.searchClauseTransitiveClosure(numTables, fromList.hashJoinSpecified());
}
/** Put the expression trees in conjunctive normal form
*
* @return None.
*
* @exception StandardException Thrown on error
*/
private void normExpressions()
throws StandardException
{
/* For each expression tree:
* o Eliminate NOTs (eliminateNots())
* o Ensure that there is an AndNode on top of every
* top level expression. (putAndsOnTop())
* o Finish the job (changeToCNF())
*/
if (whereClause != null)
{
whereClause = whereClause.eliminateNots(false);
if (SanityManager.DEBUG)
{
if (!(whereClause.verifyEliminateNots()) )
{
whereClause.treePrint();
SanityManager.THROWASSERT(
"whereClause in invalid form: " + whereClause);
}
}
whereClause = whereClause.putAndsOnTop();
if (SanityManager.DEBUG)
{
if (! ((whereClause instanceof AndNode) &&
(whereClause.verifyPutAndsOnTop())) )
{
whereClause.treePrint();
SanityManager.THROWASSERT(
"whereClause in invalid form: " + whereClause);
}
}
whereClause = whereClause.changeToCNF(true);
if (SanityManager.DEBUG)
{
if (! ((whereClause instanceof AndNode) &&
(whereClause.verifyChangeToCNF())) )
{
whereClause.treePrint();
SanityManager.THROWASSERT(
"whereClause in invalid form: " + whereClause);
}
}
}
}
/**
* Add a new predicate to the list. This is useful when doing subquery
* transformations, when we build a new predicate with the left side of
* the subquery operator and the subquery's result column.
*
* @param predicate The predicate to add
*
* @return ResultSetNode The new top of the tree.
*
* @exception StandardException Thrown on error
*/
public ResultSetNode addNewPredicate(Predicate predicate)
throws StandardException
{
wherePredicates.addPredicate(predicate);
return this;
}
/**
* Evaluate whether or not the subquery in a FromSubquery is flattenable.
* Currently, a FSqry is flattenable if all of the following are true:
* o Subquery is a SelectNode. (ie, not a RowResultSetNode or a UnionNode)
* o It contains a single table in its FROM list.
* o It contains no subqueries in the SELECT list.
* o It does not contain a group by or having clause
* o It does not contain aggregates.
* o It is not a DISTINCT.
*
* @param fromList The outer from list
*
* @return boolean Whether or not the FromSubquery is flattenable.
*/
public boolean flattenableInFromSubquery(FromList fromList)
{
if (isDistinct)
{
return false;
}
if (this.fromList.size() > 1)
{
return false;
}
/* Don't flatten (at least for now) if selectNode's SELECT list contains a subquery */
if ((selectSubquerys != null) &&
(selectSubquerys.size() > 0))
{
return false;
}
/* Don't flatten if selectNode contains a group by or having clause */
if ((groupByList != null) || generatedForHavingClause)
{
return false;
}
/* Don't flatten if select list contains something that isn't cloneable.
*/
if (! resultColumns.isCloneable())
{
return false;
}
/* Don't flatten if selectNode contains an aggregate */
if ((selectAggregates != null) &&
(selectAggregates.size() > 0))
{
return false;
}
return true;
}
/**
* Replace this SelectNode with a ProjectRestrictNode,
* since it has served its purpose.
*
* @param origFromListSize The size of the original FROM list, before
* generation of join tree.
* @return ResultSetNode new ResultSetNode atop the query tree.
*
* @exception StandardException Thrown on error
*/
public ResultSetNode genProjectRestrict(int origFromListSize)
throws StandardException
{
boolean orderingDependent = false;
PredicateList restrictionList;
ResultColumnList prRCList;
ResultSetNode prnRSN;
prnRSN = (ResultSetNode) getNodeFactory().getNode(
C_NodeTypes.PROJECT_RESTRICT_NODE,
fromList.elementAt(0), /* Child ResultSet */
resultColumns, /* Projection */
whereClause, /* Restriction */
wherePredicates,/* Restriction as PredicateList */
selectSubquerys,/* Subquerys in Projection */
whereSubquerys, /* Subquerys in Restriction */
null,
getContextManager() );
/*
** If we have aggregates OR a select list we want
** to generate a GroupByNode. In the case of a
** scalar aggregate we have no grouping columns.
**
** JRESOLVE: what about correlated aggregates from another
** block.
*/
if (((selectAggregates != null) && (selectAggregates.size() > 0))
|| (groupByList != null))
{
GroupByNode gbn = (GroupByNode) getNodeFactory().getNode(
C_NodeTypes.GROUP_BY_NODE,
prnRSN,
groupByList,
selectAggregates,
null,
getContextManager());
gbn.considerPostOptimizeOptimizations(originalWhereClause != null);
gbn.assignCostEstimate(optimizer.getOptimizedCost());
groupByList = null;
prnRSN = gbn.getParent();
// Remember if the result is dependent on the ordering
orderingDependent = orderingDependent || gbn.getIsInSortedOrder();
}
// if it is distinct, that must also be taken care of.
if (isDistinct)
{
// We first verify that a distinct is valid on the
// RCL.
resultColumns.verifyAllOrderable();
/* See if we can push duplicate elimination into the store
* via a hash scan. This is possible iff:
* o A single table query
* o We haven't merged the order by and distinct sorts.
* (Results do not have to be in a particular order.)
* o All entries in the select's RCL are ColumnReferences.
* o No predicates (This is because we currently do not
* differentiate between columns referenced in the select
* list and columns referenced in other clauses. In other
* words, the store will do duplicate elimination based on
* all referenced columns.)
* RESOLVE - We can change this to be all referenced columns
* have to be in the select list. In that case, we need to
* refine which predicates are allowed. Basically, all predicates
* must have been pushed down to the index/table scan.(If we make
* this change, then we need to verify that non of the columns in
* the predicates are correlated columns.)
* o NOTE: The implementation of isPossibleDistinctScan() will return
* false if there is an IndexRowToBaseRow above the
* FromBaseTable. This is because all of a table's columns must come
* from the same conglomerate in order to get consistent data.
*/
if (origFromListSize == 1 &&
(! orderByAndDistinctMerged) &&
resultColumns.countNumberOfSimpleColumnReferences() == resultColumns.size() &&
prnRSN.isPossibleDistinctScan())
{
prnRSN.markForDistinctScan();
}
else
{
/* We can't do a distinct scan. Determine if we can filter out
* duplicates without a sorter.
*/
boolean inSortedOrder = isOrderedResult(resultColumns, prnRSN, !(orderByAndDistinctMerged));
prnRSN = (ResultSetNode) getNodeFactory().getNode(
C_NodeTypes.DISTINCT_NODE,
prnRSN,
new Boolean(inSortedOrder),
null,
getContextManager());
prnRSN.costEstimate = costEstimate.cloneMe();
// Remember if the result is dependent on the ordering
orderingDependent = orderingDependent || inSortedOrder;
}
}
/* Generate the OrderByNode if a sort is still required for
* the order by.
*/
if (orderByList != null)
{
if (orderByList.getSortNeeded())
{
prnRSN = (ResultSetNode) getNodeFactory().getNode(
C_NodeTypes.ORDER_BY_NODE,
prnRSN,
orderByList,
null,
getContextManager());
prnRSN.costEstimate = costEstimate.cloneMe();
}
int orderBySelect = this.getResultColumns().getOrderBySelect();
if (orderBySelect > 0)
{
ResultColumnList selectRCs = prnRSN.getResultColumns().copyListAndObjects();
int wholeSize = selectRCs.size();
for (int i = wholeSize - 1; orderBySelect > 0; i--, orderBySelect--)
selectRCs.removeElementAt(i);
selectRCs.genVirtualColumnNodes(prnRSN, prnRSN.getResultColumns());
prnRSN = (ResultSetNode) getNodeFactory().getNode(
C_NodeTypes.PROJECT_RESTRICT_NODE,
prnRSN,
selectRCs,
null,
null,
null,
null,
null,
getContextManager());
}
}
if (!(orderByList != null && orderByList.getSortNeeded()) && orderByQuery)
{
// Remember if the result is dependent on the ordering
orderingDependent = true;
}
/* If the result is ordering dependent, then we must
* tell the underlying tree. At minimum, this means no
* group fetch on an index under an IndexRowToBaseRow
* since that could lead to incorrect results. (Bug 2347.)
*/
if (orderingDependent)
{
prnRSN.markOrderingDependent();
}
/* Set the cost of this node in the generated node */
prnRSN.costEstimate = costEstimate.cloneMe();
return prnRSN;
}
/**
* Is the result of this node an ordered result set. An ordered result set
* means that the results from this node will come in a known sorted order.
* This means that the data is ordered according to the order of the elements in the RCL.
* Today, the data is considered ordered if:
* o The RCL is composed entirely of CRs or ConstantNodes
* o The underlying tree is ordered on the CRs in the order in which
* they appear in the RCL, taking equality predicates into account.
* Future Enhancements:
* o The prefix will not be required to be in order. (We will need to
* reorder the RCL and generate a PRN with an RCL in the expected order.)
*
* @return boolean Whether or not this node returns an ordered result set.
*
* @exception StandardException Thrown on error
*/
private boolean isOrderedResult(ResultColumnList resultColumns,
ResultSetNode newTopRSN,
boolean permuteOrdering)
throws StandardException
{
int rclSize = resultColumns.size();
/* Not ordered if RCL contains anything other than a ColumnReference
* or a ConstantNode.
*/
int numCRs = 0;
for (int index = 0; index < rclSize; index++)
{
ResultColumn rc = (ResultColumn) resultColumns.elementAt(index);
if (rc.getExpression() instanceof ColumnReference)
{
numCRs++;
}
else if (! (rc.getExpression() instanceof ConstantNode))
{
return false;
}
}
// Corner case, all constants
if (numCRs == 0)
{
return true;
}
ColumnReference[] crs = new ColumnReference[numCRs];
// Now populate the CR array and see if ordered
int crsIndex = 0;
for (int index = 0; index < rclSize; index++)
{
ResultColumn rc = (ResultColumn) resultColumns.elementAt(index);
if (rc.getExpression() instanceof ColumnReference)
{
crs[crsIndex++] = (ColumnReference) rc.getExpression();
}
}
return newTopRSN.isOrderedOn(crs, permuteOrdering, (Vector)null);
}
/**
* Ensure that the top of the RSN tree has a PredicateList.
*
* @param numTables The number of tables in the query.
* @return ResultSetNode A RSN tree with a node which has a PredicateList on top.
*
* @exception StandardException Thrown on error
*/
public ResultSetNode ensurePredicateList(int numTables)
throws StandardException
{
return this;
}
/**
* Optimize this SelectNode. This means choosing the best access path
* for each table, among other things.
*
* @param dataDictionary The DataDictionary to use for optimization
* @param predicateList The predicate list to optimize against
* @param outerRows The number of outer joining rows
*
* @return ResultSetNode The top of the optimized tree
*
* @exception StandardException Thrown on error
*/
public ResultSetNode optimize(DataDictionary dataDictionary,
PredicateList predicateList,
double outerRows)
throws StandardException
{
Optimizer optimizer;
/* Optimize any subquerys before optimizing the underlying result set */
/* selectSubquerys is always allocated at bind() time */
if (SanityManager.DEBUG)
SanityManager.ASSERT(selectSubquerys != null,
"selectSubquerys is expected to be non-null");
/* Get a new optimizer */
optimizer = getOptimizer(fromList,
wherePredicates,
dataDictionary,
orderByList);
optimizer.setOuterRows(outerRows);
/* Optimize this SelectNode */
while (optimizer.getNextPermutation())
{
while (optimizer.getNextDecoratedPermutation())
{
optimizer.costPermutation();
}
}
/* Get the cost */
costEstimate = optimizer.getOptimizedCost();
/* Update row counts if this is a scalar aggregate */
if ((selectAggregates != null) && (selectAggregates.size() > 0))
{
costEstimate.setEstimatedRowCount((long) outerRows);
costEstimate.setSingleScanRowCount(1);
}
selectSubquerys.optimize(dataDictionary, costEstimate.rowCount());
if (whereSubquerys != null && whereSubquerys.size() > 0)
{
whereSubquerys.optimize(dataDictionary, costEstimate.rowCount());
}
return this;
}
/**
* Modify the access paths according to the choices the optimizer made.
*
* @return A QueryTree with the necessary modifications made
*
* @exception StandardException Thrown on error
*/
public ResultSetNode modifyAccessPaths() throws StandardException
{
int origFromListSize = fromList.size();
ResultColumnList leftRCList;
ResultColumnList rightRCList;
ResultSetNode leftResultSet;
ResultSetNode rightResultSet;
/*
** Modify the access path for each Optimizable, as necessary
**
** This should be the same optimizer we got above.
*/
optimizer.modifyAccessPaths();
selectSubquerys.modifyAccessPaths();
if (whereSubquerys != null && whereSubquerys.size() > 0)
{
whereSubquerys.modifyAccessPaths();
}
/* Build a temp copy of the current FromList for sort elimination, etc. */
preJoinFL.removeAllElements();
preJoinFL.nondestructiveAppend(fromList);
/* Now we build a JoinNode tree from the bottom up until there is only
* a single entry in the fromList and that entry points to the top of
* the JoinNode tree.
*
* While there is still more than 1 entry in the list, create a JoinNode
* which points to the 1st 2 entries in the list. This JoinNode becomes
* the new 1st entry in the list and the 2nd entry is deleted. The
* old 1st and 2nd entries will get shallow copies of their
* ResultColumnLists. The JoinNode's ResultColumnList will be the
* concatenation of the originals from the old 1st and 2nd entries.
* The virtualColumnIds will be updated to reflect there new positions
* and each ResultColumn.expression will be replaced with a new
* VirtualColumnNode.
*/
while (fromList.size() > 1)
{
/* Get left's ResultColumnList, assign shallow copy back to it
* and create new VirtualColumnNodes for the original's
* ResultColumn.expressions.
*/
leftResultSet = (ResultSetNode) fromList.elementAt(0);
leftRCList = leftResultSet.getResultColumns();
leftResultSet.setResultColumns(leftRCList.copyListAndObjects());
leftRCList.genVirtualColumnNodes(leftResultSet, leftResultSet.resultColumns);
/* Get right's ResultColumnList, assign shallow copy back to it,
* create new VirtualColumnNodes for the original's
* ResultColumn.expressions and increment the virtualColumnIds.
* (Right gets appended to left, so only right's ids need updating.)
*/
rightResultSet = (ResultSetNode) fromList.elementAt(1);
rightRCList = rightResultSet.getResultColumns();
rightResultSet.setResultColumns(rightRCList.copyListAndObjects());
rightRCList.genVirtualColumnNodes(rightResultSet, rightResultSet.resultColumns);
rightRCList.adjustVirtualColumnIds(leftRCList.size());
/* Concatenate the 2 ResultColumnLists */
leftRCList.nondestructiveAppend(rightRCList);
/* Now we're finally ready to generate the JoinNode and have it
* replace the 1st 2 entries in the FromList.
*/
fromList.setElementAt(
(JoinNode) getNodeFactory().getNode(
C_NodeTypes.JOIN_NODE,
leftResultSet,
rightResultSet,
null,
null,
leftRCList,
null,
getContextManager()
),
0
);
fromList.removeElementAt(1);
}
return genProjectRestrict(origFromListSize);
}
/**
Determine if this select is updatable or not, for a cursor.
*/
boolean isUpdatableCursor(DataDictionary dd) throws StandardException
{
TableDescriptor targetTableDescriptor;
if (isDistinct)
{
if (SanityManager.DEBUG)
SanityManager.DEBUG("DumpUpdateCheck","cursor select has distinct");
return false;
}
if ((selectAggregates == null) || (selectAggregates.size() > 0))
{
return false;
}
if (groupByList != null || generatedForHavingClause)
{
return false;
}
if (SanityManager.DEBUG)
SanityManager.ASSERT(fromList!=null, "select must have from tables");
if (fromList.size() != 1)
{
if (SanityManager.DEBUG)
SanityManager.DEBUG("DumpUpdateCheck","cursor select has more than one from table");
return false;
}
targetTable = (FromTable)(fromList.elementAt(0));
if (targetTable instanceof FromVTI) {
return ((FromVTI) targetTable).isUpdatableCursor();
}
if (! (targetTable instanceof FromBaseTable))
{
if (SanityManager.DEBUG)
SanityManager.DEBUG("DumpUpdateCheck","cursor select has non base table as target table");
return false;
}
/* Get the TableDescriptor and verify that it is not for a
* view or a system table.
* NOTE: We need to use the base table name for the table.
* Simplest way to get it is from a FromBaseTable. We
* know that targetTable is a FromBaseTable because of check
* just above us.
* NOTE: We also need to use the base table's schema name; otherwise
* we will think it is the default schema Beetle 4417
*/
targetTableDescriptor = getTableDescriptor(
((FromBaseTable)targetTable).getBaseTableName(),
getSchemaDescriptor(((FromBaseTable)targetTable).getTableNameField().getSchemaName()));
if (targetTableDescriptor.getTableType() == TableDescriptor.SYSTEM_TABLE_TYPE)
{
if (SanityManager.DEBUG)
SanityManager.DEBUG("DumpUpdateCheck","cursor select is on system table");
return false;
}
if (targetTableDescriptor.getTableType() == TableDescriptor.VIEW_TYPE)
{
if (SanityManager.DEBUG)
SanityManager.DEBUG("DumpUpdateCheck","cursor select is on view");
return false;
}
if ((getSelectSubquerys() != null) &&
(getSelectSubquerys().size() != 0))
{
if (SanityManager.DEBUG)
SanityManager.DEBUG("DumpUpdateCheck","cursor select has subquery in SELECT list");
return false;
}
if ((getWhereSubquerys() != null) &&
(getWhereSubquerys().size() != 0))
{
if (SanityManager.DEBUG)
SanityManager.DEBUG("DumpUpdateCheck","cursor select has subquery in WHERE clause");
return false;
}
return true;
}
/**
Assumes that isCursorUpdatable has been called, and that it
is only called for updatable cursors.
*/
FromTable getCursorTargetTable()
{
if (SanityManager.DEBUG)
SanityManager.ASSERT(targetTable!=null,
"must call isUpdatableCursor() first, and must be updatable");
return targetTable;
}
/**
* Search to see if a query references the specifed table name.
*
* @param name Table name (String) to search for.
* @param baseTable Whether or not name is for a base table
*
* @return true if found, else false
*
* @exception StandardException Thrown on error
*/
public boolean referencesTarget(String name, boolean baseTable)
throws StandardException
{
if (fromList.referencesTarget(name, baseTable) ||
(selectSubquerys != null && selectSubquerys.referencesTarget(name, baseTable)) ||
(whereSubquerys != null && whereSubquerys.referencesTarget(name, baseTable))
)
{
return true;
}
return false;
}
/**
* Return whether or not this ResultSetNode contains a subquery with a
* reference to the specified target table.
*
* @param name The table name.
* @param baseTable Whether or not table is a base table.
*
* @return boolean Whether or not a reference to the table was found.
*
* @exception StandardException Thrown on error
*/
boolean subqueryReferencesTarget(String name, boolean baseTable)
throws StandardException
{
if ((selectSubquerys != null && selectSubquerys.referencesTarget(name, baseTable)) ||
(whereSubquerys != null && whereSubquerys.referencesTarget(name, baseTable))
)
{
return true;
}
return false;
}
/**
* Bind any untyped null nodes to the types in the given ResultColumnList.
*
* @param bindingRCL The ResultColumnList with the types to bind to.
*
* @exception StandardException Thrown on error
*/
public void bindUntypedNullsToResultColumns(ResultColumnList bindingRCL)
throws StandardException
{
fromList.bindUntypedNullsToResultColumns(bindingRCL);
}
/**
* Decrement (query block) level (0-based) for
* all of the tables in this ResultSet tree.
* This is useful when flattening a subquery.
*
* @param decrement The amount to decrement by.
*
* @return Nothing;
*/
void decrementLevel(int decrement)
{
/* Decrement the level in the tables */
fromList.decrementLevel(decrement);
selectSubquerys.decrementLevel(decrement);
whereSubquerys.decrementLevel(decrement);
/* Decrement the level in any CRs in predicates
* that are interesting to transitive closure.
*/
wherePredicates.decrementLevel(fromList, decrement);
}
/**
* Determine whether or not this subquery,
* the SelectNode is in a subquery, can be flattened
* into the outer query block based on a uniqueness condition.
* A uniqueness condition exists when we can guarantee
* that at most 1 row will qualify in each table in the
* subquery. This is true if every table in the from list is
* (a base table and the set of columns from the table that
* are in equality comparisons with expressions that do not
* include a column from the same table is a superset of any unique index
* on the table) or an ExistsBaseTable.
*
* @param additionalEQ Whether or not the column returned
* by this select, if it is a ColumnReference,
* is in an equality comparison.
*
* @return Whether or not this subquery can be flattened based
* on a uniqueness condition.
*
* @exception StandardException Thrown on error
*/
boolean uniqueSubquery(boolean additionalEQ)
throws StandardException
{
ColumnReference additionalCR = null;
ResultColumn rc = (ResultColumn) getResultColumns().elementAt(0);
/* Figure out if we have an additional ColumnReference
* in an equality comparison.
*/
if (additionalEQ &&
rc.getExpression() instanceof ColumnReference)
{
additionalCR = (ColumnReference) rc.getExpression();
/* ColumnReference only interesting if it is
* not correlated.
*/
if (additionalCR.getCorrelated())
{
additionalCR = null;
}
}
return fromList.returnsAtMostSingleRow((additionalCR == null) ? null : getResultColumns(),
whereClause, wherePredicates,
getDataDictionary());
}
/**
* Get the lock mode for the target of an update statement
* (a delete or update). The update mode will always be row for
* CurrentOfNodes. It will be table if there is no where clause.
*
* @see TransactionController
*
* @return The lock mode
*/
public int updateTargetLockMode()
{
/* Do row locking if there is a restriction */
return fromList.updateTargetLockMode();
}
/**
* Return whether or not this ResultSet tree is guaranteed to return
* at most 1 row based on heuristics. (A RowResultSetNode and a
* SELECT with a non-grouped aggregate will return at most 1 row.)
*
* @return Whether or not this ResultSet tree is guaranteed to return
* at most 1 row based on heuristics.
*/
boolean returnsAtMostOneRow()
{
return (groupByList == null && selectAggregates != null && selectAggregates.size() != 0);
}
/**
* Return true if the node references SESSION schema tables (temporary or permanent)
*
* @return true if references SESSION schema tables, else false
*
* @exception StandardException Thrown on error
*/
public boolean referencesSessionSchema()
throws StandardException
{
if (fromList.referencesSessionSchema() ||
(selectSubquerys != null && selectSubquerys.referencesSessionSchema()) ||
(whereSubquerys != null && whereSubquerys.referencesSessionSchema()))
return true;
return false;
}
/**
* Accept a visitor, and call v.visit()
* on child nodes as necessary.
*
* @param v the visitor
*
* @exception StandardException on error
*/
public Visitable accept(Visitor v)
throws StandardException
{
Visitable returnNode = v.visit(this);
if (v.skipChildren(this))
{
return returnNode;
}
if (!v.stopTraversal())
{
super.accept(v);
}
if (fromList != null && !v.stopTraversal())
{
fromList = (FromList)fromList.accept(v);
}
if (whereClause != null && !v.stopTraversal())
{
whereClause = (ValueNode)whereClause.accept(v);
}
if (wherePredicates != null && !v.stopTraversal())
{
wherePredicates = (PredicateList)wherePredicates.accept(v);
}
return returnNode;
}
}