google cloud bigtable column versions are not dele

问题:

We have created a table in cloud bigtable with two column families. One column family with 30 versions and the other with 1 version. However, when we query the table we are getting multiple versions of the columns for which we have set max number of versions to 1.

Table create statement:

create 'myTable', {NAME => 'cf1', VERSIONS => '30'}, {NAME => 'cf2', VERSIONS => '1'}


Describe 'myTable':

{NAME => ‘cf2’, BLOOMFILTER => ‘ROW’, VERSIONS => ‘**1**’, IN_MEMORY => ‘false’, KEEP_DELETED_CELLS => ‘FALSE’, DATA_BLOCK_ENCODING => ‘NONE’, TTL => ‘FOREVER’, COMPRESSION => ‘NONE’, MIN_VERSIONS => ‘0’, BLOCKCACHE => ‘true’, BLOCKSIZE => ‘65536’, REPLICATION_SCOPE
 => ‘0’}                                                                                                                                                                                                                                                                        
{NAME => ‘cf1’, BLOOMFILTER => ‘ROW’, VERSIONS => ‘**30**’, IN_MEMORY => ‘false’, KEEP_DELETED_CELLS => ‘FALSE’, DATA_BLOCK_ENCODING => ‘NONE’, TTL => ‘FOREVER’, COMPRESSION => ‘NONE’, MIN_VERSIONS => ‘0’, BLOCKCACHE => ‘true’, BLOCKSIZE => ‘65536’, REPLICATION_SCOPE
 => ‘0’}

How does the bigtable garbage collection work? How frequently does it delete the older versions? or are we missing something while creating the table ?

回答1:

From Bigtable Docs: Deletion of values happens opportunistically in the background, so you might still be able to read the data for several days after it has expired.

Link to docs