RowFilter

Takes a row as input and produces an alternate view of the row based on specified rules. For example, a RowFilter might trim down a row to include just the cells from columns matching a given regular expression, or might return all the cells of a row but not their values. More complicated filters can be composed out of these components to express requests such as, "within every column of a particular family, give just the two most recent cells which are older than timestamp X."

There are two broad categories of RowFilters (true filters and transformers), as well as two ways to compose simple filters into more complex ones (chains and interleaves). They work as follows:

• True filters alter the input row by excluding some of its cells wholesale from the output row. An example of a true filter is the value_regex_filter, which excludes cells whose values don't match the specified pattern. All regex true filters use RE2 syntax (https://github.com/google/re2/wiki/Syntax) in raw byte mode (RE2::Latin1), and are evaluated as full matches. An important point to keep in mind is that RE2(.) is equivalent by default to RE2([^&92;n]), meaning that it does not match newlines. When attempting to match an arbitrary byte, you should therefore use the escape sequence &92;C, which may need to be further escaped as &92;&92;C in your client language.

• Transformers alter the input row by changing the values of some of its cells in the output, without excluding them completely. Currently, the only supported transformer is the strip_value_transformer, which replaces every cell's value with the empty string.

• Chains and interleaves are described in more detail in the RowFilter.Chain and RowFilter.Interleave documentation.

The total serialized size of a RowFilter message must not exceed 20480 bytes, and RowFilters may not be nested within each other (in Chains or Interleaves) to a depth of more than 20.