HSQLDB example source code file (TableFilter.java)
The HSQLDB TableFilter.java source code
/*
* For work developed by the HSQL Development Group:
*
* Copyright (c) 2001-2010, The HSQL Development Group
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
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*
* Neither the name of the HSQL Development Group nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
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*
*
* For work originally developed by the Hypersonic SQL Group:
*
* Copyright (c) 1995-2000, The Hypersonic SQL Group.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the Hypersonic SQL Group nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE HYPERSONIC SQL GROUP,
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* This software consists of voluntary contributions made by many individuals
* on behalf of the Hypersonic SQL Group.
*/
package org.hsqldb;
import org.hsqldb.index.RowIterator;
import org.hsqldb.lib.ArrayUtil;
import org.hsqldb.lib.HashMappedList;
import org.hsqldb.lib.HsqlArrayList;
// fredt@users 20030813 - patch 1.7.2 - fix for column comparison within same table bugs #572075 and 722443
// fredt@users 20031012 - patch 1.7.2 - better OUTER JOIN implementation
// fredt@users 20031026 - patch 1.7.2 - more efficient findfirst - especially for multi-column equijoins
// implemented optimisations similart to patch 465542 by hjbush@users
/**
* This class iterates over table rows to select the rows that fulfil join
* or other conditions. It uses indexes if they are availabe.
*
* Extended in successive versions of HSQLDB.
*
* @author Thomas Mueller (Hypersonic SQL Group)
* @version 1.8.0
* @since Hypersonic SQL
*/
final class TableFilter {
static final int CONDITION_NONE = -1; // not a condition expression
static final int CONDITION_UNORDERED = 0; // not candidate for eStart or eEnd
static final int CONDITION_START_END = 1; // candidate for eStart and eEnd
static final int CONDITION_START = 2; // candidate for eStart
static final int CONDITION_END = 3; // candidate for eEnd
static final int CONDITION_OUTER = 4; // add to this
Table filterTable;
private String tableAlias;
HashMappedList columnAliases;
Index filterIndex;
private Object[] emptyData;
boolean[] usedColumns;
private Expression eStart, eEnd;
//
Expression eAnd;
//
boolean isOuterJoin; // table joined with OUTER JOIN
boolean isAssigned; // conditions have been assigned to this
//
boolean isMultiFindFirst; // findFirst() uses multi-column index
int multiFindCount; // column count to match
Expression[] findFirstExpressions; // expressions for column values
//
private RowIterator it;
Object[] currentData;
Row currentRow;
//
Object[] currentJoinData;
// addendum to the result of findFirst() and next() with isOuterJoin==true
// when the result is false, it indicates if a non-join condition caused the failure
boolean nonJoinIsNull;
// indicates current data is empty data produced for an outer join
boolean isCurrentOuter;
/**
* Constructor declaration
*
*
* @param t
* @param alias
* @param outerjoin
*/
TableFilter(Table t, String alias, HashMappedList columnList,
boolean outerjoin) {
filterTable = t;
tableAlias = alias == null ? t.getName().name
: alias;
columnAliases = columnList;
isOuterJoin = outerjoin;
emptyData = filterTable.getEmptyRowData();
usedColumns = filterTable.getNewColumnCheckList();
}
/**
* Returns the alias or the table name.
* Never returns null;
* @return
*/
String getName() {
return tableAlias;
}
/**
* Retrieves this object's filter Table object.
*
* @return this object's filter Table object
*/
Table getTable() {
return filterTable;
}
/**
* Retrieves a CONDITION_XXX code indicating how a condition
* expression can be used for a TableFilter.
*
* @param exprType an expression type code
* @return
*/
static int getConditionType(Expression e) {
int exprType = e.getType();
switch (exprType) {
case Expression.NOT_EQUAL :
case Expression.LIKE :
return CONDITION_UNORDERED;
case Expression.IN : {
return e.isQueryCorrelated ? CONDITION_NONE
: CONDITION_UNORDERED;
}
case Expression.IS_NULL :
case Expression.EQUAL : {
return CONDITION_START_END;
}
case Expression.BIGGER :
case Expression.BIGGER_EQUAL : {
return CONDITION_START;
}
case Expression.SMALLER :
case Expression.SMALLER_EQUAL : {
return CONDITION_END;
}
default : {
// not a condition so forget it
return CONDITION_NONE;
}
}
}
// TODO: Optimize
//
// The current way always chooses eStart, eEnd conditions
// using first encountered eligible index
//
// We should check if current index offers better selectivity/access
// path than previously assigned iIndex.
//
// EXAMPLE 1:
//
// CREATE TABLE t (c1 int, c2 int primary key)
// CREATE INDEX I1 ON t(c1)
// SELECT
// *
// FROM
// t
// WHERE
// c1 = | < | <= | >= | > ...
// AND
// c2 = | < | <= | >= | > ...
//
// currently always chooses iIndex / condition (c1/I1), over
// index / condition (c2/pk), whereas index / condition (c2/pk)
// may well be better, especially if condition on c2 is equality
// (condition_start_end) and conditionon(s) on c1 involve range
// (condition_start, condition_end, or some composite).
//
// Currently, the developer/client software must somehow know facts
// both about the table, the query and the way HSQLDB forms its
// plans and, based on this knowlege, perhaps decide to reverse
// order by explicitly issuing instead:
//
// SELECT
// *
// FROM
// t
// WHERE
// c2 = | < | <= | >= | > ...
// AND
// c1 = | < | <= | >= | > ...
//
// to get optimal index choice.
//
// The same thing applies to and is even worse for joins.
//
// Consider the following (highly artificial, but easy to
// understand) case:
//
// CREATE TABLE T1(ID INTEGER PRIMARY KEY, C1 INTEGER)
// CREATE INDEX I1 ON T1(C1)
// CREATE TABLE T2(ID INTEGER PRIMARY KEY, C1 INTEGER)
// CREATE INDEX I2 ON T2(C1)
//
// select * from t1, t2 where t1.c1 = t2.c1 and t1.id = t2.id
//
// Consider the worst value distribution where t1 and t2 are both
// 10,000 rows, c1 selectivity is nil (all values are identical)
// for both tables, and, say, id values span the range 0..9999
// for both tables.
//
// Then time to completion on 500 MHz Athlon testbed using memory
// tables is:
//
// 10000 row(s) in 309114 ms
//
// whereas for:
//
// select * from t1, t2 where t1.id = t2.id and t1.c1 = t2.c1
//
// time to completion is:
//
// 10000 row(s) in 471 ms
//
// Hence, the unoptimized query takes 656 times as long as the
// optimized one!!!
//
// EXAMPLE 2:
//
// If there are, say, two non-unique candidate indexes,
// and some range or equality predicates against
// them, preference should be given to the one with
// better selectivity (if the total row count of the
// table is large, otherwise the overhead of making
// the choice is probably large w.r.t. any possible
// savings). Might require maintaining some basic
// statistics or performing appropriate index probes
// at the time the plan is being generated.
/**
* Chooses certain query conditions and assigns a copy of them to this
* filter. The original condition is set to Expression.TRUE once assigned.
*
* @param condition
*
* @throws HsqlException
*/
void setConditions(Session session,
Expression condition) throws HsqlException {
setCondition(session, condition);
if (filterIndex == null) {
filterIndex = filterTable.getPrimaryIndex();
}
if (filterIndex.getVisibleColumns() == 1 || eStart == null
|| eAnd == null || eStart.exprType != Expression.EQUAL) {
return;
}
boolean[] check = filterTable.getNewColumnCheckList();
Expression[] expr = new Expression[check.length];
int colindex = eStart.getArg().getColumnNr();
HsqlArrayList indexConditions = new HsqlArrayList();
for (int i = 0; i < filterIndex.colIndex.length; i++) {
indexConditions.add(null);
}
check[colindex] = true;
expr[colindex] = eStart.getArg2();
eAnd.getEquiJoinColumns(this, check, expr, indexConditions);
int count = ArrayUtil.countStartIntIndexesInBooleanArray(
filterIndex.getColumns(), check);
if (count <= 1) {
return;
}
for (int i = count; i < filterIndex.colIndex.length; i++) {
expr[filterIndex.colIndex[i]] = null;
}
indexConditions.setSize(count);
isMultiFindFirst = true;
findFirstExpressions = expr;
multiFindCount = count;
for (int i = 1; i < indexConditions.size(); i++) {
eEnd = new Expression(Expression.AND, eEnd,
(Expression) indexConditions.get(i));
}
//
}
private void setCondition(Session session,
Expression e) throws HsqlException {
int type = e.getType();
Expression e1 = e.getArg();
Expression e2 = e.getArg2();
isAssigned = true;
if (type == Expression.AND) {
setCondition(session, e1);
setCondition(session, e2);
return;
}
if (type == Expression.OR && isOuterJoin && e.isInJoin
&& e.outerFilter == this) {
addAndCondition(e);
e.setTrue();
return;
}
int conditionType = getConditionType(e);
if (conditionType == CONDITION_NONE) {
// not a condition expression
return;
}
// fredt@users 20030813 - patch 1.7.2 - fix for column comparison within same table bugs #572075 and 722443
if (e1.getFilter() == this && e2.getFilter() == this) {
conditionType = CONDITION_UNORDERED;
} else if (e1.getFilter() == this) {
if (!e.isInJoin && isOuterJoin) {
// do not use a where condition on the second table in outer joins
return;
}
// ok include this
} else if ((e2.getFilter() == this)
&& (conditionType != CONDITION_UNORDERED)) {
// swap and try again to allow index usage
e.swapCondition();
setCondition(session, e);
return;
} else if (e1.outerFilter == this) {
// fredt - this test is last to allow swapping the terms above
conditionType = CONDITION_OUTER;
} else {
// unrelated: don't include
return;
}
// Trace.doAssert(e1.getFilter() == this, "setCondition");
if (!e2.isResolved()) {
return;
}
// fredt - condition defined in outer but not this one
if (e1.outerFilter != null && e1.outerFilter != this) {
return;
}
if (conditionType == CONDITION_UNORDERED) {
addAndCondition(e);
return;
}
if (conditionType == CONDITION_OUTER) {
addAndCondition(e);
return;
}
int i = e1.getColumnNr();
Index index = filterTable.getIndexForColumn(session, i);
if (index == null || (filterIndex != index && filterIndex != null)) {
addAndCondition(e);
return;
}
filterIndex = index;
switch (conditionType) {
case CONDITION_START_END : {
// candidate for both start and end
if ((eStart != null) || (eEnd != null)) {
addAndCondition(e);
return;
}
eStart = new Expression(e);
eEnd = eStart;
break;
}
case CONDITION_START : {
// candidate for start
if (eStart != null) {
addAndCondition(e);
return;
}
eStart = new Expression(e);
break;
}
case CONDITION_END : {
// candidate for end
if (eEnd != null) {
addAndCondition(e);
return;
}
eEnd = new Expression(e);
break;
}
}
e.setTrue();
}
/**
* Finds the first row in the table (using an index if there is one) and
* checks it against the eEnd (range) and eAnd (other conditions)
* Expression objects. (fredt)
*
* @return true if first row was found, else false
*/
boolean findFirst(Session session) throws HsqlException {
nonJoinIsNull = false;
isCurrentOuter = false;
if (filterIndex == null) {
filterIndex = filterTable.getPrimaryIndex();
}
if (isMultiFindFirst) {
boolean convertible = true;
int[] types = filterTable.getColumnTypes();
currentJoinData = filterTable.getEmptyRowData();
for (int i = 0; i < findFirstExpressions.length; i++) {
Expression e = findFirstExpressions[i];
if (e != null) {
Object value = e.getValue(session);
if (Column.compareToTypeRange(value, types[i]) != 0) {
convertible = false;
break;
}
value = Column.convertObject(value, types[i]);
currentJoinData[i] = e.getValue(session, types[i]);
}
}
it = convertible
? filterIndex.findFirstRow(session, currentJoinData,
multiFindCount)
: filterIndex.emptyIterator();
if (!it.hasNext()) {
ArrayUtil.clearArray(ArrayUtil.CLASS_CODE_OBJECT,
currentJoinData, 0,
currentJoinData.length);
}
} else if (eStart == null) {
it = eEnd == null ? filterIndex.firstRow(session)
: filterIndex.findFirstRowNotNull(session);
} else {
Object value = eStart.getArg2().getValue(session);
int valuetype = eStart.getArg2().getDataType();
int targettype = eStart.getArg().getDataType();
it = getFirstIterator(session, eStart.getType(), value, valuetype,
filterIndex, targettype);
}
while (true) {
currentRow = it.next();
if (currentRow == null) {
break;
}
currentData = currentRow.getData();
if (!(eEnd == null || eEnd.testCondition(session))) {
break;
}
if (eAnd == null || eAnd.testCondition(session)) {
return true;
}
}
currentRow = null;
currentData = emptyData;
return false;
}
static RowIterator getFirstIterator(Session session, int eType,
Object value, int valueType,
Index index,
int targetType) throws HsqlException {
RowIterator it;
int range = 0;
if (targetType != valueType) {
range = Column.compareToTypeRange(value, targetType);
}
if (range == 0) {
value = Column.convertObject(value, targetType);
it = index.findFirstRow(session, value, eType);
} else {
switch (eType) {
case Expression.BIGGER_EQUAL :
case Expression.BIGGER :
if (range < 0) {
it = index.findFirstRowNotNull(session);
break;
}
default :
it = index.emptyIterator();
}
}
return it;
}
/**
* Advances to the next available value. <p>
*
* @return true if a next value is available upon exit
*
* @throws HsqlException if a database access error occurs
*/
boolean next(Session session) throws HsqlException {
boolean result = false;
nonJoinIsNull = false;
isCurrentOuter = false;
while (true) {
currentRow = it.next();
if (currentRow == null) {
break;
}
currentData = currentRow.getData();
if (isMultiFindFirst) {
if (filterIndex.compareRowNonUnique(
session, currentJoinData, filterIndex.colIndex,
currentData, multiFindCount) != 0) {
break;
}
}
if (!(eEnd == null || eEnd.testCondition(session))) {
break;
}
if (eAnd == null || eAnd.testCondition(session)) {
result = true;
break;
}
}
if (result) {
return true;
}
if (isMultiFindFirst) {
ArrayUtil.clearArray(ArrayUtil.CLASS_CODE_OBJECT, currentJoinData,
0, currentJoinData.length);
}
currentRow = null;
currentData = emptyData;
return false;
}
boolean nextOuter(Session session) throws HsqlException {
nonJoinIsNull = false;
isCurrentOuter = true;
currentData = emptyData;
currentRow = null;
return eAnd == null || (eAnd.getFilter() != this && eAnd.isInJoin)
|| eAnd.testCondition(session);
}
/**
* Forms a new conjunction using the given condition and this filter's
* pre-existing AND condition, or sets the given condition as this filter's
* AND condition when there is no such pre-exisiting object.
*
* @param e the condition to add
*/
private void addAndCondition(Expression e) {
Expression e2 = new Expression(e);
if (eAnd == null) {
eAnd = e2;
} else {
Expression and = new Expression(Expression.AND, eAnd, e2);
eAnd = and;
}
e.setTrue();
}
/**
* Removes reference to Index to avoid possible memory leaks after alter
* table or drop index
*/
void setAsCheckFilter() {
filterIndex = null;
}
// boucheb@users 20030415 - added for debugging support
/**
* Retreives a String representation of this obejct. <p>
*
* The returned String describes this object's table, alias
* access mode, index, join mode, Start, End and And conditions.
*
* @return a String representation of this object
*/
public String describe(Session session) {
StringBuffer sb;
String temp;
Index index;
Index primaryIndex;
int[] primaryKey;
boolean hidden;
boolean fullScan;
sb = new StringBuffer();
index = filterIndex;
primaryIndex = filterTable.getPrimaryIndex();
primaryKey = filterTable.getPrimaryKey();
hidden = false;
fullScan = (eStart == null && eEnd == null);
if (index == null) {
index = primaryIndex;
}
if (index == primaryIndex && primaryKey.length == 0) {
hidden = true;
fullScan = true;
}
sb.append(super.toString()).append('\n');
sb.append("table=[").append(filterTable.getName().name).append("]\n");
sb.append("alias=[").append(tableAlias).append("]\n");
sb.append("access=[").append(fullScan ? "FULL SCAN"
: "INDEX PRED").append("]\n");
sb.append("index=[");
sb.append(index == null ? "NONE"
: index.getName() == null ? "UNNAMED"
: index.getName()
.name);
sb.append(hidden ? "[HIDDEN]]\n"
: "]\n");
sb.append("isOuterJoin=[").append(isOuterJoin).append("]\n");
temp = eStart == null ? "null"
: eStart.describe(session);
sb.append("eStart=[").append(temp).append("]\n");
temp = eEnd == null ? "null"
: eEnd.describe(session);
sb.append("eEnd=[").append(temp).append("]\n");
temp = eAnd == null ? "null"
: eAnd.describe(session);
sb.append("eAnd=[").append(temp).append("]");
return sb.toString();
}
}
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