Each assertion in the test now prints a short marker describing what
it checks, so a failure in the reference diff is self-explanatory.

The test only exercised the PostgreSQL engine path. MySQL takes the
same code path in DatabaseCatalog::isExternalDatabase, but a regression
that special-cases PostgreSQL would have slipped through. Add a MySQL
case using ATTACH (CREATE DATABASE ... ENGINE = MySQL connects eagerly,
ATTACH does not) with a short connect_timeout so the tolerated failure
is fast.

- DatabaseCatalog.h: fix grammar in the renamed comment ("are implement"
  -> "are implemented", "protect ourself" -> "protect ourselves").
- DatabaseCatalog.cpp:2244: update outdated TableNameHints comment that
  still said "Skip datalake catalogs" to reflect the broader scope.
- 04210: add an assertion that system.completions also does not list
  external databases by default.

The new stateless test runs in about 5 seconds and remains stable across repeated runs, so it should be eligible for fasttest to improve CI coverage.\n\nRef: #104416

Per review feedback from @nikitamikhaylov on PR #104416: replace the
free helper with engine-name string compare in DatabaseCatalog.cpp by
a virtual method on IDatabase. DataLake / MySQL / PostgreSQL override
to return true; the default is false, so other engines (Atomic,
Replicated, MaterializedPostgreSQL, ...) keep the right behavior
without needing to be aware of the new classification.

The naming is intentionally distinct from the existing isExternal()
("engine does not support ClickHouse internal tables") and
isDatalakeCatalog() (narrower). See the doc comment in IDatabase.h.

Fast test does not build libpq or libmysql, so CREATE DATABASE ENGINE =
PostgreSQL/MySQL silently does nothing in that environment, and the
test's reference no longer matches the actual output.

This is the same reason 01114_mysql_database_engine_segfault.sql and
03790_materialized_postgresql_nullptr_dereference.sql carry the tag.

Reverts removal in 527e58e. CI fast-test failure:
https://s3.amazonaws.com/clickhouse-test-reports/json.html?PR=104416&sha=527e58ed25888cbc3061c7c1de91e18777c227ae&name_0=PR

Co-authored-by: Kseniia Sumarokova <sumarokovakseniia@gmail.com>

Rename the database-level helper to avoid confusion with IDatabase::isExternal
and include MaterializedPostgreSQL in remote database filtering.

Pass  through the test client API for integration tests that intentionally inspect MySQL and PostgreSQL metadata in  and .

PR: #104416

CI: https://s3.amazonaws.com/clickhouse-test-reports/json.html?PR=104416&sha=158f2327e19aebbbfd2e588f15754e44210183a7&name_0=PR

Rename the new setting and `DatabaseCatalog` filtering option to use remote database terminology consistently, while keeping `show_data_lake_catalogs_in_system_tables` as the compatibility alias.

Convert the stateless coverage from `.sh` to `.sql` now that the SQL test runner can provide unique database names.

PR: #104416

Use remote database terminology consistently in comments changed by the PR and avoid the old external database wording near `isRemoteDatabase`.

PR: #104416

Explain `isExternal` in terms of database engines that do not own ClickHouse table metadata instead of using vague wording.

PR: #104416

…l-databases-setting

The merged master documentation uses `installable`; add it to the aspell ignore dictionary so the style check passes.

PR: #104416

Use `currentDatabase` after switching to each remote database so the stateless test validates filtering with the same database predicate required by the style check.

PR: #104416

Do not classify `MaterializedPostgreSQL` as a remote database. Its table
enumeration uses local `DatabaseAtomic` metadata, unlike the `PostgreSQL`
database engine remote catalog enumeration.

PR: #104416

Apply the remote database setting override to `SHOW COLUMNS` and `SHOW INDEXES`.

This keeps explicit SHOW entrypoints working for `MySQL` and `PostgreSQL` databases.

PR: #104416

Replace the `HACK` wording with a direct explanation that explicit `SHOW TABLES` should include the requested remote database.

PR: #104416

# Conflicts:
#	ci/jobs/scripts/check_style/aspell-ignore/en/aspell-dict.txt

# Conflicts:
#	ci/jobs/scripts/check_style/aspell-ignore/en/aspell-dict.txt

The `02995_new_settings_history` check now compares against the `26.5.1` baseline, so this PR-only setting must be registered in a later history block.

CI report: https://s3.amazonaws.com/clickhouse-test-reports/json.html?PR=104416&sha=c06e440163ccc3ed3f05c2b97b575b08c586f0a4&name_0=PR&name_1=Fast%20test

PR: #104416

…es-setting

Hide MySQL and PostgreSQL databases from system.tables by default