Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.iapi.types.Like

Modifier and Type	Field and Description
private static final char	anyChar
private static final char	anyString
private static final String	SUPER_STRING

Access	Constructor and Description
private	Like()

Method Summary

Modifier and Type	Method and Description
private static boolean	Returns: TRUE if the character in val and vLoc match based on straight equality or collation element based equality. Otherwise we will return FALSE. checkEquality(char[] value to compare. val, int character position in val. vLoc, char[] pattern to look for in val. pat, int character position in pat. pLoc, RuleBasedCollator null if we are dealing with UCS_BASIC character string types. If not null, then we use it to determine the equality of the 2 characters in pat and val if they are not same. collator) If the character in val matches the character in pat, then it does not matter if the database is UCS_BASIC or territory based, we simply return TRUE from the method.
pack-priv static Boolean	checkLengths(int current index into char[] val vLoc, int end index or our value vEnd, int current index into our char[] pattern pLoc, char[] pattern char [] pat, int end index of our pattern [] pEnd) checkLengths Returns null if we are not done.
pack-priv static int	getMinLen(char[] pattern, int pStart, int pEnd, boolean haveEsc, char escChar) Calculate the shortest length string that could match this pattern
public static String	Returns: The String for the >= clause greaterEqualString(String The right side of the LIKE pattern, String The escape clause escape, int Maximum length of column, for null padding maxWidth) Return the substring from the pattern for the optimization >= clause.
private static String	greaterEqualString(String like pattern to build from pattern, char the escape character in the pattern escChar) greaterEqualString -- for Escape clause only Walk the pattern character by character
public static String	greaterEqualStringFromParameter(String pattern, int maxWidth)
public static String	greaterEqualStringFromParameterWithEsc(String pattern, String escape, int maxWidth)
public static boolean	Returns: Whether or not the like comparison is still needed. isLikeComparisonNeeded(String The right side of the LIKE pattern) Return whether or not the like comparison is still needed after performing the like transformation on a constant string.
public static boolean	Returns: Whether or not the LIKE can be transformed isOptimizable(String The right side of the LIKE pattern) Determine whether or not this LIKE can be transformed into optimizable clauses.
public static String	Returns: The String for the < clause lessThanString(String The right side of the LIKE pattern, String The escape clause escape, int Maximum length of column, for null padding maxWidth) Return the substring from the pattern for the < clause.
public static String	lessThanStringFromParameter(String pattern, int maxWidth)
public static String	lessThanStringFromParameterWithEsc(String pattern, String escape, int maxWidth)
public static Boolean	Returns: null if val or pat null, otherwise true if match and false if not. like(char[] value to compare. if null, result is null. val, int length of val valLength, char[] pattern to compare. if null, result is null. pat, int length of pat patLength, char[] escape character. Must be 1 char long. if null, no escape character is used. escape, int length of escape escapeLength, RuleBasedCollator null if we are dealing with UCS_BASIC character string types. If not null, then we use it to get collation elements for characters in val and non-metacharacters in pat to do the comparison. collator) This method gets called for UCS_BASIC and territory based character string types to look for a pattern in a value string.
private static Boolean	like(char[] val, int vLoc, int vEnd, char[] pat, int pLoc, int pEnd, char[] escape, int escapeLength, RuleBasedCollator collator)
public static Boolean	like(char[] value, int valueLength, char[] pattern, int patternLength, RuleBasedCollator collator)
private static String	Returns: the string padded with 0s up to the given length padWithNulls(String The string to pad string, int Max number of characters to pad to len) Pad a string with null characters, in order to make it > and < comparable with SQLChar.
public static String	Returns: a stripped of ESC char string if no pattern chars, null otherwise stripEscapesNoPatternChars(String pattern String to search pattern, char the escape character escChar) stripEscapesNoPatternChars

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

anyChar	back to summary
private static final char anyChar

anyString	back to summary
private static final char anyString

SUPER_STRING	back to summary
private static final String SUPER_STRING

Like	back to summary
private Like()

Method Detail

checkEquality	back to summary
private static boolean checkEquality(char[] val, int vLoc, char[] pat, int pLoc, RuleBasedCollator collator) If the character in val matches the character in pat, then it does not matter if the database is UCS_BASIC or territory based, we simply return TRUE from the method. If the characters do not match and we are running with UCS_BASIC collation, then we will return FALSE. But if the database is territory based, then we want to use the Collator for the territory to determine if the Collator treats the 2 characters as equal (ie if their collation elements match, then the 2 characters are equal even if they are not the same character). Parameters val:char[] value to compare. vLoc:int character position in val. pat:char[] pattern to look for in val. pLoc:int character position in pat. collator:RuleBasedCollator null if we are dealing with UCS_BASIC character string types. If not null, then we use it to determine the equality of the 2 characters in pat and val if they are not same. Returns:boolean TRUE if the character in val and vLoc match based on straight equality or collation element based equality. Otherwise we will return FALSE.

checkEquality

back to summary

private static boolean checkEquality(char[] val, int vLoc, char[] pat, int pLoc, RuleBasedCollator collator)

If the character in val matches the character in pat, then it does not matter if the database is UCS_BASIC or territory based, we simply return TRUE from the method. If the characters do not match and we are running with UCS_BASIC collation, then we will return FALSE. But if the database is territory based, then we want to use the Collator for the territory to determine if the Collator treats the 2 characters as equal (ie if their collation elements match, then the 2 characters are equal even if they are not the same character).

Parameters

val:char[]: value to compare.
vLoc:int: character position in val.
pat:char[]: pattern to look for in val.
pLoc:int: character position in pat.
collator:RuleBasedCollator: null if we are dealing with UCS_BASIC character string types. If not null, then we use it to determine the equality of the 2 characters in pat and val if they are not same.

Returns:boolean

TRUE if the character in val and vLoc match based on straight equality or collation element based equality. Otherwise we will return FALSE.

checkLengths	back to summary
pack-priv static Boolean checkLengths(int vLoc, int vEnd, int pLoc, char[] pat, int pEnd) checkLengths Returns null if we are not done. Returns true if we are at the end of our value and pattern Returns false if there is more pattern left but out of input value Parameters vLoc:int current index into char[] val vEnd:int end index or our value pLoc:int current index into our char[] pattern pat:char[] pattern char [] pEnd:int end index of our pattern []

checkLengths

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pack-priv static Boolean checkLengths(int vLoc, int vEnd, int pLoc, char[] pat, int pEnd)

checkLengths Returns null if we are not done. Returns true if we are at the end of our value and pattern Returns false if there is more pattern left but out of input value

Parameters

vLoc:int: current index into char[] val
vEnd:int: end index or our value
pLoc:int: current index into our char[] pattern
pat:char[]: pattern char []
pEnd:int: end index of our pattern []

getMinLen	back to summary
pack-priv static int getMinLen(char[] pattern, int pStart, int pEnd, boolean haveEsc, char escChar) Calculate the shortest length string that could match this pattern

greaterEqualString	back to summary
public static String greaterEqualString(String pattern, String escape, int maxWidth) throws StandardException Return the substring from the pattern for the optimization >= clause. Parameters pattern:String The right side of the LIKE escape:String The escape clause maxWidth:int Maximum length of column, for null padding Returns:String The String for the >= clause

greaterEqualString

back to summary

public static String greaterEqualString(String pattern, String escape, int maxWidth) throws StandardException

Return the substring from the pattern for the optimization >= clause.

Parameters

pattern:String: The right side of the LIKE
escape:String: The escape clause
maxWidth:int: Maximum length of column, for null padding

Returns:String

The String for the >= clause

greaterEqualString	back to summary
private static String greaterEqualString(String pattern, char escChar) throws StandardException greaterEqualString -- for Escape clause only Walk the pattern character by character Parameters pattern:String like pattern to build from escChar:char the escape character in the pattern

greaterEqualString

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private static String greaterEqualString(String pattern, char escChar) throws StandardException

greaterEqualString -- for Escape clause only Walk the pattern character by character

Parameters

pattern:String: like pattern to build from
escChar:char: the escape character in the pattern

greaterEqualStringFromParameter	back to summary
public static String greaterEqualStringFromParameter(String pattern, int maxWidth) throws StandardException

greaterEqualStringFromParameterWithEsc	back to summary
public static String greaterEqualStringFromParameterWithEsc(String pattern, String escape, int maxWidth) throws StandardException

isLikeComparisonNeeded	back to summary
public static boolean isLikeComparisonNeeded(String pattern) Return whether or not the like comparison is still needed after performing the like transformation on a constant string. The comparison is not needed if the constant string is of the form: CONSTANT% (constant followed by a trailing %) Parameters pattern:String The right side of the LIKE Returns:boolean Whether or not the like comparison is still needed.

isLikeComparisonNeeded

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public static boolean isLikeComparisonNeeded(String pattern)

Return whether or not the like comparison is still needed after performing the like transformation on a constant string. The comparison is not needed if the constant string is of the form: CONSTANT% (constant followed by a trailing %)

Parameters

pattern:String: The right side of the LIKE

Returns:boolean

Whether or not the like comparison is still needed.

isOptimizable	back to summary
public static boolean isOptimizable(String pattern) Determine whether or not this LIKE can be transformed into optimizable clauses. It can if the pattern is non-null and if the length == 0 or the first character is not a wild card. Parameters pattern:String The right side of the LIKE Returns:boolean Whether or not the LIKE can be transformed

isOptimizable

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public static boolean isOptimizable(String pattern)

Determine whether or not this LIKE can be transformed into optimizable clauses. It can if the pattern is non-null and if the length == 0 or the first character is not a wild card.

Parameters

pattern:String: The right side of the LIKE

Returns:boolean

Whether or not the LIKE can be transformed

lessThanString	back to summary
public static String lessThanString(String pattern, String escape, int maxWidth) throws StandardException Return the substring from the pattern for the < clause. Parameters pattern:String The right side of the LIKE escape:String The escape clause maxWidth:int Maximum length of column, for null padding Returns:String The String for the < clause Exceptions StandardException: thrown if data invalid

lessThanString

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public static String lessThanString(String pattern, String escape, int maxWidth) throws StandardException

Return the substring from the pattern for the < clause.

Parameters

pattern:String: The right side of the LIKE
escape:String: The escape clause
maxWidth:int: Maximum length of column, for null padding

Returns:String

The String for the < clause

Exceptions

StandardException:: thrown if data invalid

lessThanStringFromParameter	back to summary
public static String lessThanStringFromParameter(String pattern, int maxWidth) throws StandardException

lessThanStringFromParameterWithEsc	back to summary
public static String lessThanStringFromParameterWithEsc(String pattern, String escape, int maxWidth) throws StandardException

like	back to summary
public static Boolean like(char[] val, int valLength, char[] pat, int patLength, char[] escape, int escapeLength, RuleBasedCollator collator) throws StandardException This method gets called for UCS_BASIC and territory based character string types to look for a pattern in a value string. It also deals with escape character if user has provided one. Parameters val:char[] value to compare. if null, result is null. valLength:int length of val pat:char[] pattern to compare. if null, result is null. patLength:int length of pat escape:char[] escape character. Must be 1 char long. if null, no escape character is used. escapeLength:int length of escape collator:RuleBasedCollator null if we are dealing with UCS_BASIC character string types. If not null, then we use it to get collation elements for characters in val and non-metacharacters in pat to do the comparison. Returns:Boolean null if val or pat null, otherwise true if match and false if not. Exceptions StandardException: thrown if data invalid

back to summary

public static Boolean like(char[] val, int valLength, char[] pat, int patLength, char[] escape, int escapeLength, RuleBasedCollator collator) throws StandardException

This method gets called for UCS_BASIC and territory based character string types to look for a pattern in a value string. It also deals with escape character if user has provided one.

Parameters

val:char[]: value to compare. if null, result is null.
valLength:int: length of val
pat:char[]: pattern to compare. if null, result is null.
patLength:int: length of pat
escape:char[]: escape character. Must be 1 char long. if null, no escape character is used.
escapeLength:int: length of escape
collator:RuleBasedCollator: null if we are dealing with UCS_BASIC character string types. If not null, then we use it to get collation elements for characters in val and non-metacharacters in pat to do the comparison.

Returns:Boolean

null if val or pat null, otherwise true if match and false if not.

Exceptions

StandardException:: thrown if data invalid

like	back to summary
private static Boolean like(char[] val, int vLoc, int vEnd, char[] pat, int pLoc, int pEnd, char[] escape, int escapeLength, RuleBasedCollator collator) throws StandardException

like	back to summary
public static Boolean like(char[] value, int valueLength, char[] pattern, int patternLength, RuleBasedCollator collator) throws StandardException

padWithNulls	back to summary
private static String padWithNulls(String string, int len) Pad a string with null characters, in order to make it > and < comparable with SQLChar. Parameters string:String The string to pad len:int Max number of characters to pad to Returns:String the string padded with 0s up to the given length

padWithNulls

back to summary

private static String padWithNulls(String string, int len)

Pad a string with null characters, in order to make it > and < comparable with SQLChar.

Parameters

string:String: The string to pad
len:int: Max number of characters to pad to

Returns:String

the string padded with 0s up to the given length

stripEscapesNoPatternChars	back to summary
public static String stripEscapesNoPatternChars(String pattern, char escChar) throws StandardException stripEscapesNoPatternChars Parameters pattern:String pattern String to search escChar:char the escape character Returns:String a stripped of ESC char string if no pattern chars, null otherwise Exceptions StandardException: thrown if data invalid

stripEscapesNoPatternChars

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public static String stripEscapesNoPatternChars(String pattern, char escChar) throws StandardException

stripEscapesNoPatternChars

Parameters

pattern:String: pattern String to search
escChar:char: the escape character

Returns:String

a stripped of ESC char string if no pattern chars, null otherwise

Exceptions

StandardException:: thrown if data invalid

public Class Like

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