[CASSANDRA-17357] Snapshot true size computation does not include secondary indexes

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Duplicate
• Component/s: Local/Snapshots
• Bug Category: Correctness - API / Semantic Definition
• Severity: Low
• Complexity: Normal
• Discovered By: Code Inspection
• Platform: All
• Assignee: Paulo Motta
• Reporter: Paulo Motta

Authors

Paulo Motta

• Created: 07/Feb/22 23:16
• Updated: 11/May/22 18:16
• Resolved: 11/May/22 18:16

Description

The true size is supposed to show the total size of the snapshot minus any live sstables.

Nevertheless, sstables from secondary indexes are not included in the computation of the true size, causing a mismatch between the true size and snapshot size when there are indexes and no live sstables.

It's possible to fetch the global snapshot size per table and indexes separately via nodetool tablestats, but not for individual snapshots.

This behavior seems to be there since before 3.0, so I think it has always been like this.

Reproduction steps:

% ccm node1 nodetool -- snapshot -t test test_ks

Requested creating snapshot(s) for [test_ks] with snapshot name [test]
Snapshot directory: test

% ccm node1 nodetool listsnapshots

Snapshot Details:
Snapshot name Keyspace name Column family name True size Size on disk
test          test_ks       tbl                0 bytes   10.76 KB

Total TrueDiskSpaceUsed: 0 bytes

% ccm node1 nodetool tablestats test_ks.tbl | grep -i snapshot
    Space used by snapshots (total): 0

% ccm node1 nodetool tablestats test_ks.tbl.tbl_val_idx | grep -i snapshot
    Space used by snapshots (total): 0

% ccm node1 nodetool compact test_ks tbl.tbl_val_idx

% ccm node1 nodetool compact test_ks tbl_val_idx

% ccm node1 nodetool tablestats test_ks.tbl | grep -i snapshot
    Space used by snapshots (total): 5027

% ccm node1 nodetool tablestats test_ks.tbl.tbl_val_idx | grep -i snapshot
    Space used by snapshots (total): 5060

% ccm node1 nodetool listsnapshots

Snapshot Details:
Snapshot name Keyspace name Column family name True size Size on disk
test          test_ks       tbl                4.91 KB   10.76 KB

Total TrueDiskSpaceUsed: 4.91 KB

Issue Links

• Discovered while testing: CASSANDRA-17267 Snapshot true size is miscalculated
• is fixed by: CASSANDRA-16843 List snapshots of dropped tables
• relates to: CASSANDRA-16843 List snapshots of dropped tables