In 2.x, seems series ids may be possible to be incomplete in series id set cache?

[Rachelint]

Steps to reproduce: I am reading 2.x source codes recently, and found series ids seems can be incomplete in some cases? I am not so sure about it...

The tagValueCache's normal filling path seems like:

• Search series ids by tag key + tag value from each partition(include current inactive log file, active log file, index file) in Index::TagValueSeriesIDIterator.
• Build the multi level index measurement -> tag key -> tag value -> series ids in Index::TagValueSeriesIDIterator.
• Append the new log(include new series and its index entries) into active log file in Index::CreateSeriesIfNotExists or index::CreateSeriesListIfNotExists.
• Insert the new series id if the measurement -> tag key -> tag value -> series ids path above exist in cache in Index::CreateSeriesIfNotExists or index::CreateSeriesListIfNotExists.

However, due to multithreading, the order of steps can be:

• Search series ids by tag key + tag value from each partition(include current inactive log file, active log file, index file) in Index::TagValueSeriesIDIterator.
• Append the new log(include new series and its index entries) into active log file in Index::CreateSeriesIfNotExists or index::CreateSeriesListIfNotExists.
• Try to Insert the new series id, but found the measurement -> tag key -> tag value -> series ids path non-exist in cache in Index::CreateSeriesIfNotExists or index::CreateSeriesListIfNotExists.
• Build the multi level index measurement -> tag key -> tag value -> series ids in Index::TagValueSeriesIDIterator.

And in the later query, because the measurement -> tag key -> tag value -> series ids exists, it won't try to search from files again, so the series ids have no changes to become complete...

Expected behaviour: Complete series ids in cache.

Actual behaviour: Maybe incomplete series ids in cache.

Environment info:

Config:

Logs: