try to update and pin both spanner versions

Author: taddes

.github/workflows/main-workflow.yml

@@ -837,7 +837,7 @@ jobs:
     services:
       spanner-emulator:
         # SPANNER_EMULATOR_VER (unit tests) — keep in sync with docker/docker-compose.spanner.yaml
-        image: gcr.io/cloud-spanner-emulator/emulator:1.4.0
+        image: gcr.io/cloud-spanner-emulator/emulator:1.5.52
         ports:
           - 9010:9010
           - 9020:9020

docker/docker-compose.spanner.yaml

@@ -1,15 +1,7 @@
 services:
   sync-db:
-    # Getting sporadic errors in spanner.
-    # These errors are "INTERNAL: ZETASQL_RET_CHECK failure"
-    # in the `backend/query/query_engine.cc` file for spanner.
-    # These result in a 500 error, which causes the test to fail.
-    # I believe come from the SQL parser, but am not sure. I am
-    # unable to produce these errors locally, and am using the cited
-    # version.
     # SPANNER_EMULATOR_VER (e2e/integration tests) — keep in sync with .github/workflows/main-workflow.yml
-    # Pinned to 1.5.13 (not 1.4.0) to avoid sporadic "INTERNAL: ZETASQL_RET_CHECK failure" errors.
-    image: gcr.io/cloud-spanner-emulator/emulator:1.5.13
+    image: gcr.io/cloud-spanner-emulator/emulator:1.5.52
     ports:
       - "9010:9010"
       - "9020:9020"

docs/src/introduction.md

@@ -357,10 +357,10 @@ Google supports an in-memory Spanner emulator, which can run on your local machi
 
 **Updating the emulator version:** The emulator version is pinned in two places, each marked with `SPANNER_EMULATOR_VER`:
 
-- `docker/docker-compose.spanner.yaml` — used for e2e/integration tests (currently pinned to a specific version to avoid ZetaSQL query engine errors; see the comment there before bumping)
+- `docker/docker-compose.spanner.yaml` — used for e2e/integration tests
 - `.github/workflows/main-workflow.yml` — used for CI unit tests
 
-When upgrading, update both and verify that neither the ZetaSQL issue nor any new regressions appear in CI.
+Both should always be set to the same version. When upgrading, update both and verify no regressions appear in CI.
 
 ##### Quick Setup Using prepare-spanner.sh