Accumulo

Appendix B. Metadata Table

The metadata table contains a row for every tablet in Accumulo. Tablets are uniquely described by the ID of their table and the last row in the range assigned to the tablet, or end row. Table B-1 describes the columns that can appear in a tablet’s row in the metadata table, and Table B-2 shows some sample entries from a real metadata table.

In addition to tablet entries, there is a section of the metadata table that records file deletion entries. There is also a section for files that are in the process of being bulk-imported into Accumulo, to assist the garbage collector in not deleting these files prematurely. More about file deletion can be found in “Garbage Collector”.

Table B-1. Metadata table description

Row	Column family	Column qualifier	Value
table id ; tablet end row	file	regular data file name	size in bytes , number of keys
table id ; tablet end row	future	tablet server session id	tserver IP : port
table id ; tablet end row	last	tablet server session id	tserver IP : port
table id ; tablet end row	loc	tablet server session id	tserver IP : port
table id ; tablet end row	log	server / log file name	log set | table id
table id ; tablet end row	scan	file currently being scanned
table id ; tablet end row	srv	compact	compaction id
table id ; tablet end row	srv	dir	tablet directory
table id ; tablet end row	srv	flush	flush id
table id ; tablet end row	srv	lock	zookeeper lock location
table id ; tablet end row	srv	time	M