/*
* Copyright 2004-2014 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.expression;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import org.h2.api.ErrorCode;
import org.h2.engine.Database;
import org.h2.engine.Session;
import org.h2.index.IndexCondition;
import org.h2.message.DbException;
import org.h2.table.ColumnResolver;
import org.h2.table.TableFilter;
import org.h2.value.CompareMode;
import org.h2.value.Value;
import org.h2.value.ValueBoolean;
import org.h2.value.ValueNull;
import org.h2.value.ValueString;
/**
* Pattern matching comparison expression: WHERE NAME LIKE ?
*/
public class CompareLike extends Condition {
private static final int MATCH = 0, ONE = 1, ANY = 2;
private final CompareMode compareMode;
private final String defaultEscape;
private Expression left;
private Expression right;
private Expression escape;
private boolean isInit;
private char[] patternChars;
private String patternString;
/** one of MATCH / ONE / ANY */
private int[] patternTypes;
private int patternLength;
private final boolean regexp;
private Pattern patternRegexp;
private boolean ignoreCase;
private boolean fastCompare;
private boolean invalidPattern;
/** indicates that we can shortcut the comparison and use startsWith */
private boolean shortcutToStartsWith;
/** indicates that we can shortcut the comparison and use endsWith */
private boolean shortcutToEndsWith;
/** indicates that we can shortcut the comparison and use contains */
private boolean shortcutToContains;
public CompareLike(Database db, Expression left, Expression right,
Expression escape, boolean regexp) {
this(db.getCompareMode(), db.getSettings().defaultEscape, left, right,
escape, regexp);
}
public CompareLike(CompareMode compareMode, String defaultEscape,
Expression left, Expression right, Expression escape, boolean regexp) {
this.compareMode = compareMode;
this.defaultEscape = defaultEscape;
this.regexp = regexp;
this.left = left;
this.right = right;
this.escape = escape;
}
private static Character getEscapeChar(String s) {
return s == null || s.length() == 0 ? null : s.charAt(0);
}
@Override
public String getSQL() {
String sql;
if (regexp) {
sql = left.getSQL() + " REGEXP " + right.getSQL();
} else {
sql = left.getSQL() + " LIKE " + right.getSQL();
if (escape != null) {
sql += " ESCAPE " + escape.getSQL();
}
}
return "(" + sql + ")";
}
@Override
public Expression optimize(Session session) {
left = left.optimize(session);
right = right.optimize(session);
if (left.getType() == Value.STRING_IGNORECASE) {
ignoreCase = true;
}
if (left.isValueSet()) {
Value l = left.getValue(session);
if (l == ValueNull.INSTANCE) {
// NULL LIKE something > NULL
return ValueExpression.getNull();
}
}
if (escape != null) {
escape = escape.optimize(session);
}
if (right.isValueSet() && (escape == null || escape.isValueSet())) {
if (left.isValueSet()) {
return ValueExpression.get(getValue(session));
}
Value r = right.getValue(session);
if (r == ValueNull.INSTANCE) {
// something LIKE NULL > NULL
return ValueExpression.getNull();
}
Value e = escape == null ? null : escape.getValue(session);
if (e == ValueNull.INSTANCE) {
return ValueExpression.getNull();
}
String p = r.getString();
initPattern(p, getEscapeChar(e));
if (invalidPattern) {
return ValueExpression.getNull();
}
if ("%".equals(p)) {
// optimization for X LIKE '%': convert to X IS NOT NULL
return new Comparison(session,
Comparison.IS_NOT_NULL, left, null).optimize(session);
}
if (isFullMatch()) {
// optimization for X LIKE 'Hello': convert to X = 'Hello'
Value value = ValueString.get(patternString);
Expression expr = ValueExpression.get(value);
return new Comparison(session,
Comparison.EQUAL, left, expr).optimize(session);
}
isInit = true;
}
return this;
}
private Character getEscapeChar(Value e) {
if (e == null) {
return getEscapeChar(defaultEscape);
}
String es = e.getString();
Character esc;
if (es == null) {
esc = getEscapeChar(defaultEscape);
} else if (es.length() == 0) {
esc = null;
} else if (es.length() > 1) {
throw DbException.get(ErrorCode.LIKE_ESCAPE_ERROR_1, es);
} else {
esc = es.charAt(0);
}
return esc;
}
@Override
public void createIndexConditions(Session session, TableFilter filter) {
if (regexp) {
return;
}
if (!(left instanceof ExpressionColumn)) {
return;
}
ExpressionColumn l = (ExpressionColumn) left;
if (filter != l.getTableFilter()) {
return;
}
// parameters are always evaluatable, but
// we need to check if the value is set
// (at prepare time)
// otherwise we would need to prepare at execute time,
// which may be slower (possibly not in this case)
if (!right.isEverything(ExpressionVisitor.INDEPENDENT_VISITOR)) {
return;
}
if (escape != null &&
!escape.isEverything(ExpressionVisitor.INDEPENDENT_VISITOR)) {
return;
}
String p = right.getValue(session).getString();
if (!isInit) {
Value e = escape == null ? null : escape.getValue(session);
if (e == ValueNull.INSTANCE) {
// should already be optimized
DbException.throwInternalError();
}
initPattern(p, getEscapeChar(e));
}
if (invalidPattern) {
return;
}
if (patternLength <= 0 || patternTypes[0] != MATCH) {
// can't use an index
return;
}
int dataType = l.getColumn().getType();
if (dataType != Value.STRING && dataType != Value.STRING_IGNORECASE &&
dataType != Value.STRING_FIXED) {
// column is not a varchar - can't use the index
return;
}
// Get the MATCH prefix and see if we can create an index condition from
// that.
int maxMatch = 0;
StringBuilder buff = new StringBuilder();
while (maxMatch < patternLength && patternTypes[maxMatch] == MATCH) {
buff.append(patternChars[maxMatch++]);
}
String begin = buff.toString();
if (maxMatch == patternLength) {
filter.addIndexCondition(IndexCondition.get(Comparison.EQUAL, l,
ValueExpression.get(ValueString.get(begin))));
} else {
// TODO check if this is correct according to Unicode rules
// (code points)
String end;
if (begin.length() > 0) {
//例如like 'bcde%'
//则建立两个IndexCondition，分别是>=bcde，以及<bcdf
filter.addIndexCondition(IndexCondition.get(
Comparison.BIGGER_EQUAL, l,
ValueExpression.get(ValueString.get(begin))));
char next = begin.charAt(begin.length() - 1);
// search the 'next' unicode character (or at least a character
// that is higher)
for (int i = 1; i < 2000; i++) {
end = begin.substring(0, begin.length() - 1) + (char) (next + i);
if (compareMode.compareString(begin, end, ignoreCase) == -1) {
filter.addIndexCondition(IndexCondition.get(
Comparison.SMALLER, l,
ValueExpression.get(ValueString.get(end))));
break;
}
}
}
}
}
@Override
public Value getValue(Session session) {
Value l = left.getValue(session);
if (l == ValueNull.INSTANCE) {
return l;
}
if (!isInit) {
Value r = right.getValue(session);
if (r == ValueNull.INSTANCE) {
return r;
}
String p = r.getString();
Value e = escape == null ? null : escape.getValue(session);
if (e == ValueNull.INSTANCE) {
return ValueNull.INSTANCE;
}
initPattern(p, getEscapeChar(e));
}
if (invalidPattern) {
return ValueNull.INSTANCE;
}
String value = l.getString();
boolean result;
if (regexp) {
result = patternRegexp.matcher(value).find();
} else if (shortcutToStartsWith) {
result = value.regionMatches(ignoreCase, 0, patternString, 0, patternLength - 1);
} else if (shortcutToEndsWith) {
result = value.regionMatches(ignoreCase, value.length() -
patternLength + 1, patternString, 1, patternLength - 1);
} else if (shortcutToContains) {
String p = patternString.substring(1, patternString.length() - 1);
if (ignoreCase) {
result = containsIgnoreCase(value, p);
} else {
result = value.contains(p);
}
} else {
result = compareAt(value, 0, 0, value.length(), patternChars, patternTypes);
}
return ValueBoolean.get(result);
}
private static boolean containsIgnoreCase(String src, String what) {
final int length = what.length();
if (length == 0) {
// Empty string is contained
return true;
}
final char firstLo = Character.toLowerCase(what.charAt(0));
final char firstUp = Character.toUpperCase(what.charAt(0));
for (int i = src.length() - length; i >= 0; i--) {
// Quick check before calling the more expensive regionMatches()
final char ch = src.charAt(i);
if (ch != firstLo && ch != firstUp) {
continue;
}
if (src.regionMatches(true, i, what, 0, length)) {
return true;
}
}
return false;
}
private boolean compareAt(String s, int pi, int si, int sLen,
char[] pattern, int[] types) {
for (; pi < patternLength; pi++) {
switch (types[pi]) {
case MATCH:
if ((si >= sLen) || !compare(pattern, s, pi, si++)) {
return false;
}
break;
case ONE:
if (si++ >= sLen) {
return false;
}
break;
case ANY:
if (++pi >= patternLength) {
return true;
}
while (si < sLen) {
if (compare(pattern, s, pi, si) &&
compareAt(s, pi, si, sLen, pattern, types)) {
return true;
}
si++;
}
return false;
default:
DbException.throwInternalError("" + types[pi]);
}
}
return si == sLen;
}
private boolean compare(char[] pattern, String s, int pi, int si) {
return pattern[pi] == s.charAt(si) ||
(!fastCompare && compareMode.equalsChars(patternString, pi, s,
si, ignoreCase));
}
/**
* Test if the value matches the pattern.
*
* @param testPattern the pattern
* @param value the value
* @param escapeChar the escape character
* @return true if the value matches
*/
public boolean test(String testPattern, String value, char escapeChar) {
initPattern(testPattern, escapeChar);
if (invalidPattern) {
return false;
}
return compareAt(value, 0, 0, value.length(), patternChars, patternTypes);
}
private void initPattern(String p, Character escapeChar) {
if (compareMode.getName().equals(CompareMode.OFF) && !ignoreCase) {
fastCompare = true;
}
if (regexp) {
patternString = p;
try {
if (ignoreCase) {
patternRegexp = Pattern.compile(p, Pattern.CASE_INSENSITIVE);
} else {
patternRegexp = Pattern.compile(p);
}
} catch (PatternSyntaxException e) {
throw DbException.get(ErrorCode.LIKE_ESCAPE_ERROR_1, e, p);
}
return;
}
patternLength = 0;
if (p == null) {
patternTypes = null;
patternChars = null;
return;
}
int len = p.length();
patternChars = new char[len];
patternTypes = new int[len];
boolean lastAny = false;
for (int i = 0; i < len; i++) {
char c = p.charAt(i);
int type;
if (escapeChar != null && escapeChar == c) {
if (i >= len - 1) {
invalidPattern = true;
return;
}
c = p.charAt(++i);
type = MATCH;
lastAny = false;
} else if (c == '%') {
if (lastAny) {
continue;
}
type = ANY;
lastAny = true;
} else if (c == '_') {
type = ONE;
} else {
type = MATCH;
lastAny = false;
}
patternTypes[patternLength] = type;
patternChars[patternLength++] = c;
}
for (int i = 0; i < patternLength - 1; i++) {
if ((patternTypes[i] == ANY) && (patternTypes[i + 1] == ONE)) {
patternTypes[i] = ONE;
patternTypes[i + 1] = ANY;
}
}
patternString = new String(patternChars, 0, patternLength);
// optimizes the common case of LIKE 'foo%'
if (compareMode.getName().equals(CompareMode.OFF) && patternLength > 1) {
int maxMatch = 0;
while (maxMatch < patternLength && patternTypes[maxMatch] == MATCH) {
maxMatch++;
}
if (maxMatch == patternLength - 1 && patternTypes[patternLength - 1] == ANY) {
shortcutToStartsWith = true;
return;
}
}
// optimizes the common case of LIKE '%foo'
if (compareMode.getName().equals(CompareMode.OFF) && patternLength > 1) {
if (patternTypes[0] == ANY) {
int maxMatch = 1;
while (maxMatch < patternLength && patternTypes[maxMatch] == MATCH) {
maxMatch++;
}
if (maxMatch == patternLength) {
shortcutToEndsWith = true;
return;
}
}
}
// optimizes the common case of LIKE '%foo%'
if (compareMode.getName().equals(CompareMode.OFF) && patternLength > 2) {
if (patternTypes[0] == ANY) {
int maxMatch = 1;
while (maxMatch < patternLength && patternTypes[maxMatch] == MATCH) {
maxMatch++;
}
if (maxMatch == patternLength - 1 && patternTypes[patternLength - 1] == ANY) {
shortcutToContains = true;
}
}
}
}
private boolean isFullMatch() {
if (patternTypes == null) {
return false;
}
for (int type : patternTypes) {
if (type != MATCH) {
return false;
}
}
return true;
}
@Override
public void mapColumns(ColumnResolver resolver, int level) {
left.mapColumns(resolver, level);
right.mapColumns(resolver, level);
if (escape != null) {
escape.mapColumns(resolver, level);
}
}
@Override
public void setEvaluatable(TableFilter tableFilter, boolean b) {
left.setEvaluatable(tableFilter, b);
right.setEvaluatable(tableFilter, b);
if (escape != null) {
escape.setEvaluatable(tableFilter, b);
}
}
@Override
public void updateAggregate(Session session) {
left.updateAggregate(session);
right.updateAggregate(session);
if (escape != null) {
escape.updateAggregate(session);
}
}
@Override
public boolean isEverything(ExpressionVisitor visitor) {
return left.isEverything(visitor) && right.isEverything(visitor)
&& (escape == null || escape.isEverything(visitor));
}
@Override
public int getCost() {
return left.getCost() + right.getCost() + 3;
}
}