[MCOL-492] Vacuum function to clear unused segments Created: 2017-01-04 Updated: 2023-11-21 Resolved: 2017-01-04 |
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| Status: | Closed |
| Project: | MariaDB ColumnStore |
| Component/s: | None |
| Affects Version/s: | 1.0.6.1 |
| Fix Version/s: | Icebox |
| Type: | New Feature | Priority: | Major |
| Reporter: | Nivesh | Assignee: | Todd Stoffel (Inactive) |
| Resolution: | Won't Do | Votes: | 0 |
| Labels: | None | ||
| Environment: |
Redhat 7 |
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| Description |
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The commands below show reserved space vs used space on the dbroots. databaseSizeReport -s [schemaname] -t [tablename] (show reserved space) a new feature needs to be introduced to clean/vacuum/delete unused space in reserved segments. |
| Comments |
| Comment by Dipti Joshi (Inactive) [ 2017-01-04 ] |
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MariaDB ColumnStore reserves space in unit of extents. An extent is 8 million rows. So if you have less than 8 million rows for a table, it is going to reserve minimum 1 extent worth of space. So the space reserved is for as many extents as ceiling of (number of rows/8 million). Thus all the extents for a table will be full except for the last extent. This is the only case in which used space will be less than reserved space. It is not due to fragmentation from deletes or drop partitions. When you drop a partition - space for all the extents in the partition is released. So vacuum operation is not applicable for mariadb columnstore. |
| Comment by Dipti Joshi (Inactive) [ 2017-01-04 ] |
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As explained in the comment vacuum is not applicable to mariadb columnstore |
| Comment by Nivesh [ 2017-01-05 ] |
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Thanks for the info Dipti. |