org.hbase.async

Class KeyRegexpFilter

java.lang.Object

org.hbase.async.ScanFilter

org.hbase.async.KeyRegexpFilter

public final class KeyRegexpFilter
extends ScanFilter

Filters rows based on an expression applied to the row key.

The regular expression will be applied on the server-side, on the row key. Rows for which the key doesn't match will not be returned to the scanner, which can be useful to carefully select which rows are matched when you can't just do a prefix match, and cut down the amount of data transfered on the network.

Don't use an expensive regular expression, because Java's implementation uses backtracking and matching will happen on the server side, potentially on many many row keys. See Regular Expression Matching Can Be Simple And Fast for more details on regular expression performance (or lack thereof) and what "backtracking" means.

This means you need to be careful about using regular expressions supplied by users as that would allow them to easily DDoS HBase by sending prohibitively expensive regexps that would consume all CPU cycles and cause the entire HBase node to time out.

Since:

1.5

Constructor Summary

Constructors

Constructor and Description
KeyRegexpFilter(byte[] regexp) Sets a regular expression to filter results based on the row key.
KeyRegexpFilter(byte[] regexp, Charset charset) Sets a regular expression to filter results based on the row key.
KeyRegexpFilter(String regexp) Sets a regular expression to filter results based on the row key.
KeyRegexpFilter(String regexp, Charset charset) Sets a regular expression to filter results based on the row key.

Method Summary

Modifier and Type	Method and Description
Charset	getCharset()
byte[]	getRegexp()
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

KeyRegexpFilter

public KeyRegexpFilter(String regexp)

Sets a regular expression to filter results based on the row key.

This is equivalent to calling KeyRegexpFilter(String, Charset) with the ISO-8859-1 charset in argument.

Parameters:

regexp - The regular expression with which to filter the row keys.

KeyRegexpFilter

public KeyRegexpFilter(String regexp,
                       Charset charset)

Sets a regular expression to filter results based on the row key.

Parameters:

regexp - The regular expression with which to filter the row keys.

charset - The charset used to decode the bytes of the row key into a string. The RegionServer must support this charset, otherwise it will unexpectedly close the connection the first time you attempt to use this scanner.

See Also:

KeyRegexpFilter(byte[], Charset)

KeyRegexpFilter

public KeyRegexpFilter(byte[] regexp)

Sets a regular expression to filter results based on the row key.

This is equivalent to calling KeyRegexpFilter(byte[], Charset) with the ISO-8859-1 charset in argument.

Parameters:

regexp - The binary regular expression with which to filter the row keys.

KeyRegexpFilter

public KeyRegexpFilter(byte[] regexp,
                       Charset charset)

Sets a regular expression to filter results based on the row key.

Parameters:

regexp - The regular expression with which to filter the row keys.

charset - The charset used to decode the bytes of the row key into a string. The RegionServer must support this charset, otherwise it will unexpectedly close the connection the first time you attempt to use this scanner.

Method Detail

getRegexp

public byte[] getRegexp()

Returns:

the regular expression, a copy of the byte array

Since:

1.8

getCharset

public Charset getCharset()

Returns:

the character set for this regular expression

Since:

1.8

toString

public String toString()

Overrides:

toString in class Object