How to Check the Compression and Distribution of an Append-Only Table
Post date: Nov 02, 2012 11:15:32 PM
Greenplum provides built-in functions to check the compression ratio and the distribution of an append-only table. Both functions take either the object ID or name of a table. The table name may be qualified with a schema name.
Function Return Type Description
get_ao_distribution(name) Set of (dbid, tuplecount) rows Shows the distribution of rows of an append-only table across the array. Returns a set of rows,
get_ao_distribution(oid) each of which includes a segment dbid and the number of tuples stored on the segment.
get_ao_compression_ratio(name) float8 Calculates the compression ratio for a compressed append-only table. If information is not
get_ao_compression_ratio(oid) available, this function returns a value of -1.