more operations;

tuned signature;

tuned signature: more uniform SQL.Data instances;

tuned signature;

tuned signature;

disable write_updates from f425bbc4b2eb for now: "isabelle build_process -rf" does not quite work yet;

revert part of 5969ead9f900 that does not quite work yet: only one accidental host is used;

record updates within database, based on serial;

proper tables (amending 4611b7b47b42);

tuned;

clarified signature: improved data integrity;

clarified modules;

clarified modules;

obsolete;

misc tuning: prefer Build_Process.Update operations;

misc tuning and clarification: prefer explicit type Build_Process.Update;

misc tuning and clarification;

tuned signature;

clarified data representation: more uniform treatment of State.Pending vs. State.Running;

tuned: drop pointless SQL.order_by (see also 5f706f7c624b);

upgrade pretty_maybe_quote following 2746dfc9ceae;

tuned;

eliminate odd aliases (see also 2746dfc9ceae);

tuned signature: prefer bottom-up construction;

tuned;

tuned signature;

clarified signature;

tuned;