Hello, Matthias!
>> - I notice you've added a new argument to
>> heapam_index_build_range_scan. I think this could just as well be
>> implemented by reading the indexInfo->ii_Concurrent field, as the
>> values should be equivalent, right?
> Not always; currently, it is set by ResetSnapshotsAllowed[5].
> We fall back to regular index build if there is a predicate or expression in the index (which should be considered "safe" according to [6]).
> However, we may remove this check later.
> Additionally, there is no sense in resetting the snapshot if we already have an xmin assigned to the backend for some reason.
I realized you were right. It's always possible to reset snapshots for concurrent index building without any limitations related to predicates or expressions.
Additionally, the PROC_IN_SAFE_IC flag is no longer necessary since snapshots are rotating quickly, and it's possible to wait for them without requiring any special exceptions for CREATE/REINDEX INDEX CONCURRENTLY.
Currently, it looks like this [1]. I've also attached a single large patch just for the case.
I plan to restructure the patch into the following set:
* Introduce catalogXmin as a separate value to calculate the horizon for the catalog.
* Add the STIR access method.
* Modify concurrent build/reindex to use an aux-index approach without snapshot rotation.
* Add support for snapshot rotation for non-parallel and non-unique cases.
* Extend support for snapshot rotation in parallel index builds.
* Implement snapshot rotation support for unique indexes.
Best regards,
Mikhail