A bug and an error from rewrite

[jwj61]

A call of

db.nf_fields.rewrite(mod, reindex=False, restat=False)

finished with the text below. It

• clearly recreated indices even though it was told not to
• had an error, probably related to recent changes

Looking at the results, the rewrite succeeded, i.e., the error happened after the fact.

Created index nf_fields_relative_class_number in 45.116 secs
2025-07-20 03:34:01,114 - ALTER TABLE "nf_fields_tmp" ADD CONSTRAINT "nf_fields_tmp_pkey" PRIMARY KEY (id) ran in 44.27398085594177s
2025-07-20 03:34:39,133 - ALTER TABLE "nf_fields_extras_tmp" ADD CONSTRAINT "nf_fields_extras_tmp_pkey" PRIMARY KEY (id) ran in 38.01786208152771s
Built primary key on nf_fields in 82.293 secs
resorting disabled
2025-07-20 04:34:23,421 - UPDATE "nf_fields_extras_tmp" SET "dirichlet_group" = "tmp_update_from_file"."dirichlet_group", "frobs" = "tmp_update_from_file"."frobs", "res" = "tmp_update_from_file"."res", "source" = "tmp_update_from_file"."source", "subfield_inclusions" = "tmp_update_from_file"."subfield_inclusions", "torsion_gen" = "tmp_update_from_file"."torsion_gen", "units" = "tmp_update_from_file"."units", "unitsGmodule" = "tmp_update_from_file"."unitsGmodule", "unitsType" = "tmp_update_from_file"."unitsType", "zk" = "tmp_update_from_file"."zk" FROM "tmp_update_from_file" WHERE "nf_fields_extras_tmp"."id" = "tmp_update_from_file"."id" ran in 3584.2863030433655s
Swapped temporary tables for nf_fields into place in 0.3204059600830078 secs
New backup at nf_fields_old2
WARNING: there are now 2 backup tables for nf_fields
You should probably run db.nf_fields.cleanup_from_reload() to save disc space
Updated nf_fields in 12833.157 secs
Traceback (most recent call last):
File "/scratch/home/jj/lmfdb/domaxcm.py", line 21, in
db.nf_fields.rewrite(mod, reindex=False, restat=False)
File "/scratch/sage/sage-10.3/local/var/lib/sage/venv-python3.10/lib/python3.10/site-packages/psycodict/table.py", line 1031, in rewrite
self.log_db_change("rewrite", query=query, projection=projection)
File "/scratch/sage/sage-10.3/local/var/lib/sage/venv-python3.10/lib/python3.10/site-packages/psycodict/table.py", line 2515, in log_db_change
self._db.log_db_change(operation, tablename=self.search_table, **data)
File "/scratch/home/jj/lmfdb/lmfdb/lmfdb_database.py", line 366, in log_db_change
self._execute(inserter, [uid, datetime.datetime.now(datetime.UTC), tablename, operation, data])
AttributeError: module 'datetime' has no attribute 'UTC'

[roed314]

The import error should be fixed by #6584. For the reindex, the problem is that rewrite uses reload under the hood (so that reload_revert is available and so that we don't take out locks on tables that are being actively used on beta). Unfortunately, reload is not compatible with reindex=False since SQL is actually creating a whole new table to swap in, so there's no alternative to recreating the indexes. I think the right solution is to update the documentation of several functions to emphasize this, and perhaps raise an error if the user tries to explicitly set reindex=False.