tests: enable vectored get only in regress tests

.github/workflows/build_and_test.yml

@@ -472,6 +472,7 @@ jobs:
           CHECK_ONDISK_DATA_COMPATIBILITY: nonempty
           BUILD_TAG: ${{ needs.tag.outputs.build-tag }}
           PAGESERVER_VIRTUAL_FILE_IO_ENGINE: std-fs
+          PAGESERVER_GET_VECTORED_IMPL: vectored
 
       - name: Merge and upload coverage data
         if: matrix.build_type == 'debug' && matrix.pg_version == 'v14'

test_runner/fixtures/neon_fixtures.py

@@ -486,6 +486,11 @@ class NeonEnvBuilder:
 
         self.pageserver_virtual_file_io_engine: Optional[str] = pageserver_virtual_file_io_engine
 
+        self.pageserver_get_vectored_impl: Optional[str] = None
+        if os.getenv("PAGESERVER_GET_VECTORED_IMPL", "") == "vectored":
+            self.pageserver_get_vectored_impl = "vectored"
+            log.debug('Overriding pageserver get_vectored_impl config to "vectored"')
+
         assert test_name.startswith(
             "test_"
         ), "Unexpectedly instantiated from outside a test function"
@@ -1053,6 +1058,8 @@ class NeonEnv:
             }
             if self.pageserver_virtual_file_io_engine is not None:
                 ps_cfg["virtual_file_io_engine"] = self.pageserver_virtual_file_io_engine
+            if config.pageserver_get_vectored_impl is not None:
+                ps_cfg["get_vectored_impl"] = config.pageserver_get_vectored_impl
 
             # Create a corresponding NeonPageserver object
             self.pageservers.append(

test_runner/regress/test_compatibility.py

@@ -226,6 +226,10 @@ def test_forward_compatibility(
     )
 
     try:
+        # TODO: remove this once the previous pageserrver version understands
+        # the 'get_vectored_impl' config
+        neon_env_builder.pageserver_get_vectored_impl = None
+
         neon_env_builder.num_safekeepers = 3
         neon_local_binpath = neon_env_builder.neon_binpath
         env = neon_env_builder.from_repo_dir(