Will MongoDB Query planner cache data get replicated to secondary from primary?

[Manoj Vivek]

Hi All,

I have a strange problem in mongoDb index selection that makes me ask this question, Does Query planner cache data get replicated to secondaries from primary?

I have a mongoDB cluster running version 2.2, with one primary, one secondary and one hidden secondary. The hidden secondary is used for offline analytics.

I have index 'A' in all servers. And index 'B' in hidden secondary alone(not in other servers) covering analytics queries. Here index 'A' and 'B' has overlapping fields. B covers the analytics query fully, But A partially covers the query. The hidden secondary doesn't receive any query that uses index A, only primary and secondary receives query satisfied by index A. 

But when the analytics query is given, the hidden secondary selects index 'A' instead of index 'B', which fully covers the query.

Can anyone face this issue?

Also is there anyway to view query planner cache data in 2.2 ( like in 2.6)?

-Manoj Vivek

[Asya Kamsky]

There is no replication of query plans.

In 2.2 you can't see the cached plan info but you can run query with explain(true) on a typical query and if you post that here maybe we can see why index A is being selected over index B.

Asya

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