# Index scripts

The basic format is one or more field names followed by a colon, followed by one or more actions. Some actions take an optional or required parameter.

Since Omega 1.4.6, the parameter value can be enclosed in double quotes, which is necessary if it contains whitespace; it's also needed for parameter values containing a comma for actions which support multiple parameters (such as `split`) since there unquoted commas are interpreted as separating parameters.

Since Omega 1.4.8, the following C-like escape sequences are supported for parameter values enclosed in double quotes: `\\`, `\"`, `\0`, `\t`, `\n`, `\r`, and `\x` followed by two hex digits.

The actions are applied in the specified order to each field listed, and fields can be listed in several lines.

Comments are allowed on a line by themselves, introduced by a `#`.

Here's an example:

    desc1 : unhtml index truncate=200 field=sample
    desc2 desc3 desc4 : unhtml index
    # This is a comment.
    name : field=caption weight=3 index
    ref : field=ref boolean=Q unique=Q
    type : field=type boolean=XT

Don't put spaces around the `=` separating an action and its argument - current versions allow spaces here (though this was never documented as supported) but it leads to a missing argument quietly swallowing the next action rather than using an empty value or giving an error, e.g. this takes `hash` as the field name, which is unlikely to be what was intended:

    url : field= hash boolean=Q unique=Q

Since 1.4.6 a deprecation warning is emitted for spaces before or after the `=`.

The actions are:

boolean[=PREFIX]
  index the text as a single boolean term (with prefix PREFIX). If there's no text, no term is added. Omega expects certain prefixes to be used for certain purposes - those starting "X" are reserved for user applications. `Q` is conventionally used as the prefix for a unique ID term.
date=FORMAT

  generate `D`-, `M`- and `Y`-prefixed terms for date range searching (e.g. `D20021221`, `M200212` and `Y2002` for the 21st December 2002). The following values for FORMAT are supported:

  > - `unix`: the value is interpreted as a Unix local time_t (seconds since the start of 1970 in the local timezone).
  > - `unixutc`: the value is interpreted as a Unix UTC time_t (seconds since the start of 1970 in UTC). (Since Omega 1.4.12)
  > - `yyyymmdd`: the value is interpreted as an 8 digit string, e.g. 20021221 for 21st December 2002.

  Unknown formats give an error at script parse time since Omega 1.4.12 (in earlier versions unknown formats uselessly resulted in the terms `D`, `M` and `Y` literally being added to every document).

  Invalid values result in no terms being added (and since Omega 1.4.12 a warning is emitted).

field[=FIELDNAME]
  add as a field to the Xapian record. FIELDNAME defaults to the field name in the dumpfile. It is valid to have more than one instance of a given field: all instances will be processed and stored in the Xapian record.
gap[=SIZE]
  leave a gap of SIZE term positions. SIZE defaults to 100. This provides a way to stop phrases, `NEAR` and `ADJ` from matching across fields.
hash[=LENGTH]
  Xapian has a limit on the length of a term. To handle arbitrarily long URLs as terms, omindex implements a scheme where the end of a long URL is hashed (short URLs are left as-is). You can use this same scheme in scriptindex. LENGTH defaults to 239, which if you index with prefix "U" produces url terms compatible with omindex. If specified, LENGTH must be at least 6 (because the hash takes 6 characters).
hextobin

  converts pairs of hex digits to binary byte values (providing a way to specify arbitrary binary strings e.g. for use in a document value slot). The input must have an even length and be composed entirely of hex digits (if it isn't, an error is reported).

  `hextobin` was added in Omega 1.4.6. Prior to Omega 1.4.20, the "error" on a bad value was really handled like a warning - it didn't cause Omega to exit with non-zero status, instead the value was passed on unchanged.

index[=PREFIX]
  split text into words and index (with prefix PREFIX if specified).
indexnopos[=PREFIX]
  split text into words and index (with prefix PREFIX if specified), but don't include positional information in the database - this makes the database smaller, but phrase searching won't work.
load

  reads the contents of the file using the current text as the filename and then sets the current text to the contents. If the current text is empty, a warning is issued (since Xapian 1.4.10). If the file can't be loaded (not found, wrong permissions, etc) then an error is issued and scriptindex exits (prior to Omega 1.4.20 this "error" was really handled as a warning - scriptindex continued with the current text set to empty, and the final exit status wasn't affected).

  If the next action is `truncate`, then scriptindex is smart enough to know it only needs to load the start of a large file.

lower
  lowercase the text (useful for generating boolean terms)
ltrim[=CHARACTERSTOTRIM]

  remove leading characters from the text which are in `CHARACTERSTOTRIM` (default: space, tab, formfeed, vertical tab, carriage return, linefeed).

  Currently only ASCII characters are supported in `CHARACTERSTOTRIM`.

  See also `rtrim`, `squash` and `trim`.

  `ltrim` was added in Omega 1.4.19.

parsedate=FORMAT

  parse the text as a date string using `strptime()` (or C++11's `std::get_time()` on platforms without `strptime()`) with the format specified by `FORMAT`, and set the text to the result as a Unix `time_t` (seconds since the start of 1970 in UTC), which can then be fed into `date=unixutc` or `valuepacked`, for example:

      last_update : parsedate="%Y%m%d %T" field=lastmod valuepacked=0

  Format strings containing `%Z` are rejected with an error, as it seems that `strptime()` implementations don't properly support this (glibc's just accepts any sequence of non-whitespace and ignores it).

  Format strings containing `%z` are only supported on platforms where `struct tm` has a `tm_gmtoff` member, which is needed to correctly apply the timezone offset. On other platforms `%z` is also rejected with an error.

  `parsedate` was added in Omega 1.4.6.

rtrim[=CHARACTERSTOTRIM]

  remove trailing characters from the text which are in `CHARACTERSTOTRIM` (default: space, tab, formfeed, vertical tab, carriage return, linefeed).

  Currently only ASCII characters are supported in `CHARACTERSTOTRIM`.

  See also `ltrim`, `squash` and `trim`.

  `rtrim` was added in Omega 1.4.19.

spell
  Generate spelling correction data for any `index` or `indexnopos` actions in the remainder of this list of actions.
split=DELIMITER[,OPERATION]

  Split the text at each occurrence of `DELIMITER`, discard any empty strings, perform `OPERATION` on the resulting list, and then for each entry perform all the actions which follow `split` in the current rule.

  `OPERATION` can be `dedup` (remove second and subsequent occurrences from the list of any value), `prefixes` (which instead of just giving the text between delimiters, gives the text up to each delimiter), `sort` (sort), or `none` (default: none).

  If you want to specify `,` for delimiter, you need to quote it, e.g. `split=",",dedup`.

squash[=CHARACTERSTOTRIM]

  replace runs of one or more characters from `CHARACTERSTOTRIM` in the text with a single space. Leading and trailing runs are removed entirely.

  `CHARACTERSTOTRIM` defaults to: space, tab, formfeed, vertical tab, carriage return, linefeed).

  Currently only ASCII characters are supported in `CHARACTERSTOTRIM`.

  See also `ltrim`, `rtrim` and `trim`.

  `squash` was added in Omega 1.4.19.

trim[=CHARACTERSTOTRIM]

  remove leading and trailing characters from the text which are in `CHARACTERSTOTRIM` (default: space, tab, formfeed, vertical tab, carriage return, linefeed).

  Currently only ASCII characters are supported in `CHARACTERSTOTRIM`.

  See also `ltrim`, `rtrim` and `squash`.

  `trim` was added in Omega 1.4.19.

truncate=LENGTH
  truncate to at most LENGTH bytes, but avoid chopping off a word (useful for sample and title fields)
unhtml
  strip out HTML tags
unique[=PREFIX[,missing=MISSINGACTION]]

  use the value in this field for a unique ID. If the value is empty, a warning is issued but nothing else is done. Only one record with each value of the ID may be present in the index: adding a new record with an ID which is already present will cause the old record to be replaced or deleted.

  Deletion happens if the only input field present has the `unique` action applied to it. (Prior to 1.5.0, if there were multiple lists of actions applied to an input field this triggered replacement instead of deletion). If you want to suppress this deletion feature, supplying a dummy input field which doesn't match the index script will achieve this.

  You should also index the field as a boolean field using the same prefix so that the old record can be found. In Omega, `Q` is conventionally used as the prefix of a unique term.

  You can use `unique` at most once in each index script (this is only enforced since Omega 1.4.5, but older versions didn't handle multiple instances usefully).

  The optional `missing` parameter is supported since Omega 1.4.20. It controls what happens when a record is processed which doesn't trigger the `unique` action or triggers the `unique` action with an empty value. It can be one of:

  > - `error`: Exit with an error upon encountering such a document (default in Omega >= 1.5.0)
  > - `new`: Create a new document (default in Omega < 1.4.20 when `unique` not triggered)
  > - `warn+new`: Issue a warning and create a new document (default in Omega >= 1.4.20 and in older versions when `unique` is triggered with an empty value)
  > - `skip`: Move on to the next record
  > - `warn+skip`: Issue a warning and move on to the next record

value=VALUESLOT
  add as a Xapian document value in slot VALUESLOT. Values can be used for collapsing equivalent documents, sorting the MSet, etc. If you want to perform numeric sorting, use the valuenumeric action instead.
valuenumeric=VALUESLOT
  Like value=VALUESLOT, this adds as a Xapian document value in slot VALUESLOT, but it first encodes for numeric sorting using Xapian::sortable_serialise(). Values set with this action can be used for numeric sorting of the MSet.
valuepacked=VALUESLOT

  Like value=VALUESLOT, this adds as a Xapian document value in slot VALUESLOT, but it first encodes as a 4 byte big-endian binary string. If the input is a Unix time_t value, the resulting slot can be used for date range filtering and to sort the MSet by date. Can be used in combination with `parsedate`, for example:

      last_update : parsedate="%Y%m%d %T" field=lastmod valuepacked=0

  `valuepacked` was added in Omega 1.4.6.

weight=FACTOR
  set the weighting factor to FACTOR (a non-negative integer) for any `index` or `indexnopos` actions in the remainder of this list of actions. The default is 1. Use this to add extra weight to titles, keyword fields, etc, so that words in them are regarded as more important by searches.

# Input files:

The data to be indexed is read in from one or more input files. Each input file consists of zero or more records, each separated by one or more blank lines.

Omega 1.4.20 and later explicitly allow multiple blank lines between records, and also blank lines before the first record and after the last record - in earlier versions only a single blank line after each record was explicitly handled, and extra blank lines were handled as an empty records. If you want to be compatible with older versions we recommend a single blank line after each record (with the blank line after the final record being optional).

Each record contains one or more fields of the form "name=value". If value contains newlines, these must be escaped by inserting an equals sign ('=') after each newline. Here's an example record:

    id=ghq147
    title=Sample Record
    value=This is a multi-line
    =value.  Note how each newline
    =is escaped.
    format=HTML

# Example:

See mbox2omega and mbox2omega.script for an example of how you can generate a dump file from an external source and write an index script to be used with it. Try "mbox2omega --help" for more information.