feat: disable described statement cache timeout by default (GoogleCloudPlatform#4409)

* feat: disable described statement cache timeout by default

The timeout for the described statements cache was set to 30 minutes by default. This default
is now set to Long.MAX_VALUE, as elements in this cache are (almost) never invalidated. They
would only be invalidated if the data type of an existing column would change while the
application is running, which is a very rare event. The added number of roundtrips that are
added by invalidating elements in this cache once every 30 minutes does not weigh up against
the tiny probability that any elements are actually invalid.

* build: add expected system table

Author: olavloite

.ci/e2e-expected/backslash-dt.txt

@@ -47,6 +47,7 @@
  testdb_e2e_psql_v?? | spanner_sys        | column_operations_stats_10minute | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
  testdb_e2e_psql_v?? | spanner_sys        | column_operations_stats_hour     | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
  testdb_e2e_psql_v?? | spanner_sys        | column_operations_stats_minute   | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
+ testdb_e2e_psql_v?? | spanner_sys        | graph_operation_execution_status | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
  testdb_e2e_psql_v?? | spanner_sys        | lock_stats_top_10minute          | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
  testdb_e2e_psql_v?? | spanner_sys        | lock_stats_top_hour              | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
  testdb_e2e_psql_v?? | spanner_sys        | lock_stats_top_minute            | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
@@ -91,5 +92,5 @@
  testdb_e2e_psql_v?? | spanner_sys        | txn_stats_total_minute           | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
  testdb_e2e_psql_v?? | spanner_sys        | user_split_points                | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
  testdb_e2e_psql_v?? | spanner_sys        | vector_index_metrics_history     | VIEW       |                              |                      |                           |                          |                        |                    |          |               |                   |                  |               |                 |
-(90 rows)
+(91 rows)
 

src/main/java/com/google/cloud/spanner/pgadapter/metadata/OptionsMetadata.java

@@ -707,7 +707,11 @@ public enum DdlTransactionMode {
   private static final String OPTION_DESCRIBE_CACHE_EXPIRE_MINUTES =
       "describe_cache_expire_minutes";
   private static final String OPTION_DESCRIBE_CACHE_MAX_SIZE = "describe_cache_max_size";
-  private static final long DEFAULT_DESCRIBE_CACHE_EXPIRE_MINUTES = 30L;
+  // The default for this cache is not to expire elements. The reason is that the values in this
+  // cache would only be invalidated if the datatype of an existing column would change, which is
+  // highly unlikely to occur for a production system.
+  private static final long DEFAULT_DESCRIBE_CACHE_EXPIRE_MINUTES =
+      Duration.ofSeconds(Long.MAX_VALUE).toMinutes();
   private static final long DEFAULT_DESCRIBE_CACHE_MAX_SIZE = 5000L;
 
   private final Map<String, String> environment;

src/test/java/com/google/cloud/spanner/pgadapter/metadata/OptionsMetadataTest.java

@@ -40,6 +40,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.PrintStream;
+import java.time.Duration;
 import java.util.Collections;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -101,7 +102,8 @@ public void testCustomMaxBacklog() {
   public void testDefaultDescribeCacheOptions() {
     OptionsMetadata options =
         new OptionsMetadata(new String[] {"-p", "p", "-i", "i", "-c", "credentials.json"});
-    assertEquals(30L, options.getDescribeCacheExpireMinutes());
+    assertEquals(
+        Duration.ofSeconds(Long.MAX_VALUE).toMinutes(), options.getDescribeCacheExpireMinutes());
     assertEquals(5000L, options.getDescribeCacheMaxSize());
   }