/*
* Reconcile and resolve conflicts for incoming versioning events.
*
* This function handles both events generated locally and remotely by other
* backends.
*
* When a new versioning event is received at the Local MDVSN,
* look up if the same object has a conflicting version locally.
*
* If a conflict is detected, resolve by generating a new version for
* the "combined" object. We don't generate a new VE for the conflict.
* This means the combined object version is only visible to the
* current backend.
*
* event: The new event to be considered
* local_entry: The conflicting entry in the Local MDVSN cache
*/
static void
mdver_localhandler_reconcile(mdver_event *event, mdver_entry *local_entry)
{
#ifdef MD_VERSIONING_INSTRUMENTATION
char *mdev_str = mdver_event_str(event);
elog(gp_mdversioning_loglevel, "Local VE Handler: Reconcile: Local entry = %d: (%d, %d). Incoming event %s",
local_entry->key,
(int) local_entry->ddl_version,
(int) local_entry->dml_version,
mdev_str);
pfree(mdev_str);
#endif
uint64 new_ddl_version = event->new_ddl_version;
uint64 new_dml_version = event->new_dml_version;
bool conflict = false;
if (local_entry->ddl_version != event->old_ddl_version)
{
new_ddl_version = mdver_next_global_version();
conflict = true;
}
if (local_entry->dml_version != event->old_dml_version)
{
new_dml_version = mdver_next_global_version();
conflict = true;
}
#if MD_VERSIONING_INSTRUMENTATION
if (conflict)
{
elog(gp_mdversioning_loglevel, "Local VE Handler: Conflict resolved. New"
"version generated, updated local entry to %d : (%d,%d) -> (%d, %d)",
local_entry->key,
(int) local_entry->ddl_version, (int) local_entry->dml_version,
(int) new_ddl_version, (int) new_dml_version);
}
else
{
elog(gp_mdversioning_loglevel, "Local VE Handler: No conflict. Update local entry to %d : (%d,%d) -> (%d, %d)",
local_entry->key,
(int) event->old_ddl_version, (int) event->old_dml_version,
(int) event->new_ddl_version, (int) event->new_dml_version);
}
#endif
/* Update local entry with the resolved versions */
local_entry->ddl_version = new_ddl_version;
local_entry->dml_version = new_dml_version;
}
/*
* When a backend is requesting the more recent version of an object,
* if the Local MDVSN cache doesn't have the version, and if a NUKE event
* has been encountered in the current transaction, a new version is
* generated and returned for the object. A new versioning event is also
* produced.
*
* key: The key of the looked-up object
* ddl_version: used to return the ddl version for the object
* dml_version: used to return the dml version for the object
*
*/
static void
mdver_request_after_nuke(Oid key, uint64 *ddl_version, uint64 *dml_version)
{
Assert(NULL != ddl_version);
Assert(NULL != dml_version);
/* Generate new version */
*ddl_version = mdver_next_global_version();
*dml_version = mdver_next_global_version();
mdver_event *new_event = (mdver_event *) palloc0(sizeof(mdver_event));
new_event->key = key;
new_event->new_ddl_version = *ddl_version;
new_event->new_dml_version = *dml_version;
new_event->old_ddl_version = INVALID_MD_VERSION;
new_event->old_dml_version = INVALID_MD_VERSION;
#ifdef MD_VERSIONING_INSTRUMENTATION
/* Add my current process id as the originating backend pid */
new_event->backend_pid = MyProcPid;
#endif
/* Annotate Versioning Event with the current version from Global MDVSN if exists */
mdver_entry *crt_entry = mdver_glob_mdvsn_find(key);
if (NULL != crt_entry)
{
new_event->old_ddl_version = crt_entry->ddl_version;
new_event->old_dml_version = crt_entry->dml_version;
}
CacheAddVersioningEvent(new_event);
#ifdef MD_VERSIONING_INSTRUMENTATION
char *mdev_str = mdver_event_str(new_event);
ereport(gp_mdversioning_loglevel,
(errmsg("mdver_consume_after_nuke: generated new VE %s",
mdev_str),
errprintstack(false)));
pfree(mdev_str);
#endif
/* A copy of the event is added to the queue above. We can pfree our local copy */
pfree(new_event);
}
/*
* Entry point for the Local Versioning Event Handler. This gets called
* for every message that is executed locally at a backend.
*/
extern void
mdver_localhandler_new_event(SharedInvalidationMessage *msg)
{
Assert(NULL != msg);
Assert(SHAREDVERSIONINGMSG_ID == msg->id);
#ifdef MD_VERSIONING_INSTRUMENTATION
char *mdev_str = mdver_event_str(&msg->ve.verEvent);
ereport(gp_mdversioning_loglevel,
(errmsg("LocalExecuteVE: got %s event %s",
msg->ve.local ? "LOCAL" : "REMOTE",
mdev_str),
errprintstack(false)));
pfree(mdev_str);
#endif
/*
* There are some cases where we don't have a transInvalInfo structure,
* and thus we don't have a Local MDVSN. For example:
* - an auxiliary process (fts prober comes to mind) that queries
* catalog tables directly using heap functions (no transaction)
* - updating persistent tables during transaction commit
* (transInvalInfo has already been reset).
* - bootstrap
*
* In other cases, we simply don't have a Local MDVSN since we don't
* cache versions:
* - a QE process running on the master or segments will have a
* syscache, but not a Metadata Version cache
*
* In those cases we don't care about versioning, so skip adding
* to local MDVSN.
*/
mdver_local_mdvsn *local_mdvsn = GetCurrentLocalMDVSN();
if (NULL != local_mdvsn)
{
mdver_event *event = &msg->ve.verEvent;
if (mdver_is_nuke_event(event))
{
elog(gp_mdversioning_loglevel, "Local VE Handler: Received NUKE event");
mdver_local_mdvsn_nuke(local_mdvsn);
return;
}
if (msg->ve.local)
{
/*
* Locally generated event, we must add or update the version
* in the Local MDVSN.
*/
mdver_entry entry;
entry.key = event->key;
/* FIXME gcaragea 7/4/2014: Can we assert anything here? */
entry.ddl_version = event->new_ddl_version;
entry.dml_version = event->new_dml_version;
mdver_local_mdvsn_add(local_mdvsn, &entry, msg->ve.local);
}
else
{
/*
* An event coming from the global queue (GVQ)
* If we are interested in this object, add / update
* version in Local MDVSN.
*
*/
mdver_entry *local_entry = mdver_local_mdvsn_find(local_mdvsn, event->key);
if (NULL != local_entry)
{
/*
* A VE came from SVQ for a key that we already have locally.
* Need to reconcile and record.
*/
mdver_localhandler_reconcile(event, local_entry);
}
else
{
elog(gp_mdversioning_loglevel, "Local VE Handler: Ignoring remote event for object not of interest key=%d", event->key);
}
/* TODO gcaragea 5/27/2014: For subtransactions, keep all messages (MPP-22935) */
}
}
}