Important Since version 2.2 we use a different algorithm for tracking changed pages. Thus, data recorded in the ptrack.map using pre 2.2 versions of ptrack is incompatible with newer versions. After extension upgrade and server restart old ptrack.map will be discarded with WARNING and initialized from the scratch.

• ptrack now uses two slots to record page change information. It
  helps significantly reduce number of false positives with the same
  ptrack.map_size. See #5 for details. Many thanks to @funny-falcon for
  ideas, theory and review!
• ptrack_get_pagemapset() now also displays a number of changed blocks
  per file.
• Added ptrack_get_change_stat(start_lsn pg_lsn) that can desplay statistic
  of changes (number of files, pages and size in MB) since specified start_lsn.