Merge branch 'drop-constraint-fixes'
Merge remote-tracking branch 'github/master'
Replace the (unused) table list with a TableName list.
Remove the affectedTables altogether.
Clean up the imports
merge tjoneslo: Remove affectedTables set from PostgresBaseOperatorStatement

Merge pull request #1113 from tjoneslo/sql-layer/base-operator-memory-leak
https://github.com/FoundationDB/sql-layer/pull/1113