I am working on a project which requires me to create a background worker. This
worker checks some array(shared memory) every second and then connects to the
database mentioned within the array. That is I want to connect to different
databases using the same background worker without killing it.
Here is what I tried:
BackgroundWorkerInitializeConnection(“db1", NULL, 0);
//reconnect to another database for that first cleanup
if (IsTransactionState())
{
ereport(LOG, (errmsg("aborting current transaction")));
AbortCurrentTransaction();
}
if (MyProcPort)
{
ereport(LOG, (errmsg("closing connection")));
closesocket(MyProcPort->sock);
MyProcPort = NULL;
}
AtEOXact_Files(false);
AtEOXact_Buffers(false);
MyDatabaseId = InvalidOid;
MyDatabaseTableSpace = InvalidOid;
InitializeTimeouts();
ResetCatalogCaches();
DeinitCatalogCache();
DisablePortalManager();
BackgroundWorkerInitializeConnection(“db2", NULL, 0);
==================
* DisablePortalManager
* Clean up the portal manager by destroying the hash table and memory
context.
*/
void
DisablePortalManager(void)
{
if (PortalHashTable)
{
hash_destroy(PortalHashTable);
PortalHashTable = NULL;
}
if (TopPortalContext)
{
MemoryContextDelete(TopPortalContext);
TopPortalContext = NULL;
}
}
===================
* DeinitCatCache
* Releases all memory associated with a catalog cache entry
*/
void
DeinitCatCache(CatCache *cache)
{
if (!cache)
return;
/* Free all the cached tuples */
for (uint32 i = 0; i < cache->cc_nbuckets; i++)
{
dlist_mutable_iter iter;
dlist_foreach_modify(iter, &cache->cc_bucket[i])
{
CatCTup *ct = dlist_container(CatCTup, cache_elem, iter.cur);
dlist_delete(iter.cur);
pfree(ct);
}
}
/* Free the bucket array */
if (cache->cc_bucket)
pfree(cache->cc_bucket);
cache->cc_bucket = NULL;
/* Free all CatCList entries */
dlist_mutable_iter list_iter;
dlist_foreach_modify(list_iter, &cache->cc_lists)
{
CatCList *cl = dlist_container(CatCList, cache_elem, list_iter.cur);
dlist_delete(&cl->cache_elem);
pfree(cl);
}
/* Reset other fields */
cache->cc_ntup = 0;
cache->cc_nbuckets = 0;
cache->cc_nkeys = 0;
cache->cc_tupdesc = NULL;
memset(cache->cc_skey, 0, sizeof(cache->cc_skey));
cache->cc_reloid = InvalidOid;
cache->cc_indexoid = InvalidOid;
cache->yb_cc_is_fully_loaded = false;
/* Don't free cache itself - that's handled by the memory context */
}
/*
* DeinitCatalogCache
* Deinitialize the catalog cache system, freeing allocated memory
* and resetting state to allow reinitialization.
*/
void
DeinitCatalogCache(void)
{
int cacheId;
/* Only proceed if cache is actually initialized */
if (!CacheInitialized)
return;
/* Free each individual cache */
for (cacheId = 0; cacheId < SysCacheSize; cacheId++)
{
if (SysCache[cacheId])
{
DeinitCatCache(SysCache[cacheId]);
SysCache[cacheId] = NULL;
}
}
/* Reset OID arrays */
SysCacheRelationOidSize = 0;
SysCacheSupportingRelOidSize = 0;
/* Mark cache as uninitialized */
CacheInitialized = false;
}
Wrote this by manually resolving errors one by one from InitPostgresImpl
This still does not work completely. Does anyone know a simpler way which
doesn’t require me to manually write all this?
I feel frontend(libpq) must have this functionality as when I do \c db2 then
it conection to it without killing the session.
How can we do this from backend?
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