kind

It is important to note that while filters can be chained, each is linked by an implied logical AND operation. If you want to match from one of several different patterns, as with a logical OR operation, you can do so with the pattern filtertype using regex as the kind.

This example shows how to select multiple indices based on them beginning with either alpha-, bravo-, or charlie-:

filters:
- filtertype: pattern
  kind: regex
  value: '^(alpha-|bravo-|charlie-).*$'

Explaining all of the different ways in which regular expressions can be used is outside the scope of this document, but hopefully this gives you some idea of how a regular expression pattern can be used when a logical OR is desired.

Timestrings are parsed from strftime patterns, like %Y.%m.%d, into regular expressions. For example, %Y is 4 digits, so the regular expression for that looks like \d{{4}}, and %m is 2 digits, so the regular expression is \d{{2}}.

What this means is that a simple timestring to match year and month, %Y.%m will result in a regular expression like this: ^.*\d{{4}}\.\d{{2}}.*$. This pattern will match any 4 digits, followed by a period ., followed by 2 digits, occurring anywhere in the index name. This means it will match monthly indices, like index-2016.12, as well as daily indices, like index-2017.04.01, which may not be the intended behavior.

To compensate for this, when selecting indices matching a subset of another pattern, use a second filter with exclude set to True

- filtertype: pattern
 kind: timestring
 value: '%Y.%m'
- filtertype: pattern
 kind: timestring
 value: '%Y.%m.%d'
 exclude: True

This will prevent the %Y.%m pattern from matching the %Y.%m part of the daily indices.

This applies whether using timestring as a mere pattern match, or as part of date calculations.