Limit the amount of disk space that a table can use.

[BaiShaoqi]

Main purpose is to limit a table usage of disk space. and use pg_total_relation_size function to calcuate a table size.

load quota and refresh fs in one function load_quotas_refresh_fs_model.
Main logic is following
SPI_execute("select relationid, pg_total_relation_size(relationid) int8, quota int8 from quota.config", true, 0);

Have a question I would like to consult you, on applying disk quota on greenplum, you have said in README:

Quotas are only checked at the beginning of INSERT and COPY statements.
As long as the user has not exceeded the quota at the beginning of the
statement, the INSERT or COPY is allowed to go through, even if it
causes the quota to be exceeded.

how can greenplum overcome the weakness: allow COPY to cancel on the progress once disk usage is higher than quota not after the query has done, would like to hear your ideas.