Switch compute-related locales to C.UTF-8 by default

Right now, our environments create databases with the C locale, which is
really unfortunate for users who have data stored in other languages
that they want to analyze. For instance, show_trgm on Hebrew text
currently doesn't work in staging or production.

I don't envision this being the final solution. I think this is just a
way to set a known value so the pageserver doesn't use its parent
environment. The final solution to me is exposing initdb parameters to
users in the console. Then they could use a different locale or encoding
if they so chose.

Signed-off-by: Tristan Partin <tristan@neon.tech>

test_runner/regress/test_compute_locales.py

@@ -0,0 +1,61 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, cast
+
+from fixtures.pg_version import PgVersion
+
+if TYPE_CHECKING:
+    from collections.abc import Sequence
+
+    from fixtures.neon_fixtures import NeonEnv
+
+
+def test_default_locales(neon_simple_env: NeonEnv):
+    """
+    Test that the default locales for compute databases is C.UTF-8.
+    """
+    env = neon_simple_env
+
+    endpoint = env.endpoints.create_start("main")
+
+    domain_locales = cast(
+        "Sequence[str]",
+        endpoint.safe_psql(
+            "SELECT current_setting('lc_messages') AS lc_messages,"
+            + "current_setting('lc_monetary') AS lc_monetary,"
+            + "current_setting('lc_numeric') AS lc_numeric,"
+            + "current_setting('lc_time') AS lc_time"
+        )[0],
+    )
+    for dl in domain_locales:
+        assert dl == "C.UTF-8"
+
+    # Postgres 15 added the locale providers
+    if env.pg_version < PgVersion.V15:
+        results = cast(
+            "Sequence[str]",
+            endpoint.safe_psql(
+                "SELECT datcollate, datctype FROM pg_database WHERE datname = current_database()"
+            )[0],
+        )
+
+        datcollate = results[0]
+        datctype = results[1]
+    else:
+        results = cast(
+            "Sequence[str]",
+            endpoint.safe_psql(
+                "SELECT datlocprovider, datcollate, datctype FROM pg_database WHERE datname = current_database()"
+            )[0],
+        )
+        datlocprovider = results[0]
+        datcollate = results[1]
+        datctype = results[2]
+
+        if env.pg_version >= PgVersion.V17:
+            assert datlocprovider == "b", "The locale provider is not builtin"
+        else:
+            assert datlocprovider == "c", "The locale provider is not libc"
+
+    assert datcollate == "C.UTF-8"
+    assert datctype == "C.UTF-8"

test_runner/regress/test_wal_restore.py

@@ -64,6 +64,7 @@ def test_wal_restore(
                 ),
                 str(data_dir),
                 str(port),
+                env.pg_version,
             ]
         )
         restored.start()
@@ -127,6 +128,7 @@ def test_wal_restore_initdb(
                 ),
                 str(data_dir),
                 str(port),
+                env.pg_version,
             ]
         )
         restored.start()