This commit changes the checkpointing to determine a minimum WAL ID
for readers and a max ID based on the writer. Pages are checkpointed
from the WAL up to the writer's max WAL ID but segments are removed
only up to the reader's minimum WAL ID. This ensures that WAL pages
are not removed out from under current read transactions.
Previously, RBF shared a list of WAL segments between the DB & Tx.
However, this increased the need for mutexes to access the data.
WAL segments are effectively immutable on-disk so the list of segments
has been refactored so that changes to the segment list are done via
copy-on-write which allows read transactions to access segment data
without a mutex.
The database checkpointing can remove early, unused segments and
there is an update/add check to make sure that Tx segments pushed back
to the DB do not include removed segments.
- blue_green for doing migration. Called before Holder.Open finishes.
- holdbkg.go added for index lookup. Less wedging between a deadlock and a race.
- fix fault under read-only map under lmdb at
TestExecutor_Execute_Row_Range/RowIDColumnID by doing cow in roaring.
- roaring -tags gofuzz builds again
- roaringparanoia build tag added to make test targets in Makefile
- add rbf.NewDBWithAllocZero for out-of-bounds memory checks
- .circleci/config.yml test-shardwidth-22 with large run container, kept OOM-ing we suspect.
Fixes#819
This commit adds the ability to start a transaction with an exclusive
lock for the entire database. This ensures no other read or write
transactions can run at the same time. Writes in this mode write
directly to the database and skip the WAL entirely.
