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From "Peter Ciuffetti (JIRA)" <>
Subject [jira] [Created] (NUTCH-2058) Indexer plugin that allows RegEx replacements on the NutchDocument field values
Date Thu, 02 Jul 2015 20:41:05 GMT
Peter Ciuffetti created NUTCH-2058:

             Summary: Indexer plugin that allows RegEx replacements on the NutchDocument field
                 Key: NUTCH-2058
             Project: Nutch
          Issue Type: Improvement
          Components: indexer
            Reporter: Peter Ciuffetti

This is the description of a IndexingFilter plugin I'm developing that allows regex replacements
on field values prior to indexing to your search engine.

*Plugin name*: index-replace

*Property name*: index.replace.regexp

*Use case example:*

I'm indexing Nutch-created documents to a pre-existing SOLR core.  In this case I need to
coerce the documents into the schema and field formats expected by the existing core.  The
features of index-static and solrindex-mapping.xml get me most of the way.  Among other things,
I need to generate identifiers from the web URLs.  So I need to do something like a regex
replace on the id provided and then (with solrindex-mapping.xml) move this to the field name
defined by the existing core.

Another use case might be to refactor all URLs stored in the document so they route through
a redirector gateway.

The following is from the draft description in nutch-default.xml

Allows indexing-time regexp replace manipulation of metadata fields. The format of the property
is a list of regexp replacements, one line per field being modified.  To use this property,
add index-replace to your list of activated plugins.

Field names would be one of those from The replacements
will happen in the order listed. If a field needs multiple replacement operations they may
be listed more than once.

The *field name* precedes the equal sign.  The first character after the equal sign signifies
the delimiter for the regexp, the replacement value and the flags.

The *regexp* and the optional *flags* should correspond to Pattern.compile(String regexp,
int flags) defined here:,%20int%29

The *flags* is an integer sum of the flag values defined in
(Sec: java.util.regex.Pattern)

Patterns are compiled when the plugin is initialized for efficiency.

*Escaping*: since the regexp is being read from a config file, any escaped values must be
double escaped.  Eg:  {code}
{code} will cause the escaped \s+ match pattern to be used.

The *replacement* value should correspond to Java Matcher(CharSequence input).replaceAll(String
*Multi-valued Fields*
If a field has multiple values, the replacement will be applied to each value in turn.

*Non-string Datatypes*
Replacement is possible only on String field datatypes.  If the field you name in the property
is not a String datatype, it will be silently ignored.

*Host and URL specific replacements*
If the replacements should apply only to specifc pages, then add a sequence like


When using Host and URL replacements, all replacements preceding the first hostmatch or urlmatch
will apply to all Nutch documents.  Replacements following a hostmatch or urlmatch will be
applied to Nutch documents that match the host or url field (up to the next hostmatch or urlmatch
line).  hostmatch and urlmatch patterns must be unique in this property.

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