Manage life-cycle of connections via memory contexts

Tie the life cycle of a data node connection to the memory context it
is created on. Previously, a data node connection was automatically
closed at the end of a transaction, although often a connection needs
to live beyond a single transaction. For example, a connection cache
is maintained for data node connections, and, for such cases, a flag
was set on a connection to avoid closing it automatically.

Instead of tying connections to transactions, they are now life-cycle
managed via memory contexts. This simplifies the handling of
connections and avoids having to create exceptions to closing
connections at transaction end.

CHANGELOG.md

@@ -8,6 +8,7 @@ accidentally triggering the load of a previous DB version.**
 
 **Features**
 * #5241 Allow RETURNING clause when inserting into compressed chunks
+* #5245 Mange life-cycle of connections via memory contexts
 
 **Bugfixes**
 * #4804 Skip bucketing when start or end of refresh job is null

src/cache.h

@@ -65,9 +65,7 @@ extern TSDLLEXPORT void ts_cache_init(Cache *cache);
 extern TSDLLEXPORT void ts_cache_invalidate(Cache *cache);
 extern TSDLLEXPORT void *ts_cache_fetch(Cache *cache, CacheQuery *query);
 extern TSDLLEXPORT bool ts_cache_remove(Cache *cache, void *key);
-
-extern MemoryContext ts_cache_memory_ctx(Cache *cache);
-
+extern TSDLLEXPORT MemoryContext ts_cache_memory_ctx(Cache *cache);
 extern TSDLLEXPORT Cache *ts_cache_pin(Cache *cache);
 extern TSDLLEXPORT int ts_cache_release(Cache *cache);