Mark, It specifies the group that you want to be extract after the Regex has been matched. Group numbers are 1-referenced. In the example you gave, the first group corresponds to "the", the second group corresponds to "bar". A group in Regex is specified by a pair of parenthesis.
You can also look at the source code to gain further understanding. http://www.javasourcecode.org/html/open-source/hive/hive-0.7.1/org/apache/hadoop/hive/ql/udf/UDFRegExpExtract.java.html Matcher is the API that is used to match the Regex. More on that at: http://download.oracle.com/javase/1.4.2/docs/api/java/util/regex/Matcher.html Mark ----- Original Message ----- From: "Mark Sunderlin" <mark.sunder...@teamaol.com> To: "user@hive.apache.org" <user@hive.apache.org> Sent: Thursday, October 27, 2011 1:57:08 PM Subject: Question on regexp_extract() , Index? I've been working with the hive regexp_extract(string subject, string pattern, int index) command. In the hive language manual, https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-StringFunctions, the following description for this function is given: Returns the string extracted using the pattern. e.g. regexp_extract('foothebar', 'foo(.*?)(bar)', 2) returns 'bar.' Note that some care is necessary in using predefined character classes: using '\s' as the second argument will match the letter s; ' s' is necessary to match whitespace, etc. The 'index' parameter is the Java regex Matcher group() method index. See docs/api/java/util/regex/Matcher.html for more information on the 'index' or Java regex group() method. I tried doing some basic web searches and cannot find what I seek, understanding of what the Index value in the regexp() call does. Where exactly is the information listed as, "See docs/api/java/util/regex/Matcher.html?" Is it online somewhere? --- Mark E. Sunderlin Solutions Architect |AOL Data Warehouse P: 703-256-6935 | C: 540-327-6222 AIM: MESunderlin 22000 AOL Way | Dulles, VA | 20166
