[MB-60260] Using count(*) function on system:indexes can return incorrect amount of indexes

Product: Couchbase Server
Component: Query-Service
Issue Link: MB-60260
Affects Versions: 7.0.x, 7.1.x, 7.2.x
Fix Versions: 7.2.5, 7.6.0

Summary

• The following query reports the correct number of indexes present in the cluster:

SELECT * FROM system:indexes

• However, the query below returns an incorrect count, displaying a higher number of indexes than are actually present:

SELECT COUNT(*) FROM system:indexes

Symptoms 

• The two queries report different numbers of indexes present in the cluster.

Triggers

• This issue occurs because the implementation of the COUNT function counts some indexes more than once.

Verification

• Run both queries and compare the results.
• Observe that the reported counts for the number of indexes are different

Workarounds

• There is currently no workaround for this issue. To obtain the correct count of indexes, use the query:
  SELECT * FROM system:indexes
• Alternatively, upgrade to a version of Couchbase Server that includes the fix for this issue.