MySQL ADBC driver ignores the target schema when creating an ingest table

[alxmrs]

Summary

The ADBC Driver Foundry's MySQL driver (0.6.1, the latest release at the time of writing) ignores the target schema when it creates the table for an ingest. Given db_schema_name, it creates the table in the connection's default database, then inserts into the target database, so the ingest fails.

#255 works around this in the ADBC adapter. This issue tracks the workaround until the driver is fixed.

Reproduction

MySQL 8.4.11, adbc-driver-manager 1.12.0, MySQL driver 0.6.1 (dbc install mysql):

import pyarrow as pa
from adbc_driver_manager import dbapi

con = dbapi.connect(driver="mysql", db_kwargs={"uri": "mysql://root@127.0.0.1:3306/xql"})
with con.cursor() as cur:
    cur.execute("CREATE DATABASE IF NOT EXISTS era5")
    cur.adbc_ingest("surface", pa.table({"x": [1.0]}), mode="create", db_schema_name="era5")

• Expected: a table era5.surface holding one row.

• Actual:

  ProgrammingError: NOT_FOUND: [MySQL] failed to prepare batch insert statement:
  Error 1146 (42S02): Table 'era5.surface' doesn't exist.
  

  The table was created as xql.surface, in the connection's default database, according to information_schema.tables.

Workaround in xarray-sql

For MySQL and MariaDB, xarray_sql/backends/adbc.py doesn't pass db_schema_name at all. Instead, _default_database makes the target database the connection's default (USE era5) for the duration of the ingest, then restores the previous default. MySQL can't unset a default database, so a connection that had no default keeps the target afterwards.

This is how mixed-dimension Datasets register as era5.<group> on MySQL. test_mysql_mixed_dimensions_register_in_a_database covers it; the test runs when XARRAY_SQL_TEST_MYSQL_URI is set.

Next steps

• Report upstream at adbc-drivers/mysql (no existing issue covered it at the time of writing).
• Once a fixed driver is released, remove _default_database and pass db_schema_name through on MySQL, as on every other database.

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