FAQ of the gp_fastsequence table
Article ID: 296833
Updated On:
Products
VMware Tanzu Greenplum
Issue/Introduction
What is the gp_fastsequence and what role does it play in the ao table?
gp_fastsequence is used to generate and keep track of row numbers for AO and CO tables, more preciously, the pg_aoseg.pg_aocsseg_* table information. The aocsseg_* tables are auxiliary tables of the AO table.
What type of storage it had used?
Heap table
Is this table accessible?
Yes
Will there be bloat issues for this table?
Yes, there will be residues after the AOCO table is deleted, so the vacuum is required to eliminate bloat
Where can we find the relevant information?
Doc: https://gpdb.docs.pivotal.io/6-10/ref_guide/system_catalogs/gp_fastsequence.html
Souce Code: .//src/backend/catalog/gp_fastsequence.c
A more detailed explanation:
objid： Object id of the pg_aoseg.pg_aocsseg_* table used to track append-optimized file segments.
objmod： Object modifier ---> It is more like segfile ID of the rel_file_node of the AO tables. The ao tables rel_file_node is like 123456.0 or 123456.1,123456.2. This objmod is the .1, .2 number.
last_sequence： The last sequence number used by the object. ---> Similar to EOF of the AO segfile. The bigger the rel_file_node's size is, the larger the number is.
gp_fastsequence is used to generate and keep track of row numbers for AO and CO tables, more preciously, the pg_aoseg.pg_aocsseg_* table information. The aocsseg_* tables are auxiliary tables of the AO table.
What type of storage it had used?
Heap table
Is this table accessible?
Yes
Will there be bloat issues for this table?
Yes, there will be residues after the AOCO table is deleted, so the vacuum is required to eliminate bloat
Where can we find the relevant information?
Doc: https://gpdb.docs.pivotal.io/6-10/ref_guide/system_catalogs/gp_fastsequence.html
Souce Code: .//src/backend/catalog/gp_fastsequence.c
A more detailed explanation:
objid： Object id of the pg_aoseg.pg_aocsseg_* table used to track append-optimized file segments.
objmod： Object modifier ---> It is more like segfile ID of the rel_file_node of the AO tables. The ao tables rel_file_node is like 123456.0 or 123456.1,123456.2. This objmod is the .1, .2 number.
last_sequence： The last sequence number used by the object. ---> Similar to EOF of the AO segfile. The bigger the rel_file_node's size is, the larger the number is.
Environment
Product Version: 6.21
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