/*
* Main entry point for clients that request versions for objects. Returns
* the most recent visible version of an object when requested by a
* backend/client.
*
* If no version is found, a new version for the object is generated and
* recorded in the caches. New versioning events are potentially generated
* as well if needed.
*
* This function never returns INVALID_MD_VERSION as a result.
*
* 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
*
*/
void
mdver_request_version(Oid key, uint64 *ddl_version, uint64 *dml_version)
{
Assert(NULL != ddl_version);
Assert(NULL != dml_version);
*dml_version = INVALID_MD_VERSION;
*ddl_version = INVALID_MD_VERSION;
if (!mdver_enabled())
{
/*
* MD Versioning feature is turned off. Return (1,0) as a fixed
* version so that ORCA can check for equality etc.
*/
*ddl_version = 1;
*dml_version = 0;
return;
}
/*
* Basic flow is described below. More details can be found in
* the Metadata Versioning design document.
*
* - Do a look-up in the Local MDVSN. If the object is found there,
* return its version.
* - If not found in Local MDVSN, and nuke_happened is not set,
* do a look-up in the Global MDVSN.
* - If the object is found there,
* - Add it to the Local MDVSN and
* - Return its version.
* - If the object is not in Global MDVSN
* - Generate a new version for the object
* - Record the version in Global MDVSN
* - Add new version to Local MDVSN
* - Return new version
* - If not found in Local MDVSN and nuke_happened is set, the object
* needs a new version.
* - Generate a new version for the object
* - Read current version from Global MDVSN (if exists)
* - Add a versioning event to the CVQ with the new version
* - Record the new version in the Local MDVSN
* - Return the new version.
*/
/* Try Local MDVSN first */
mdver_local_mdvsn *local_mdvsn = GetCurrentLocalMDVSN();
Assert(NULL != local_mdvsn);
mdver_entry *crt_entry = mdver_local_mdvsn_find(local_mdvsn, key);
if (NULL != crt_entry)
{
#ifdef MD_VERSIONING_INSTRUMENTATION
elog(gp_mdversioning_loglevel, "Found version in Local MDVSN: (%d, " UINT64_FORMAT ", " UINT64_FORMAT ")",
key, crt_entry->ddl_version, crt_entry->dml_version);
#endif
*ddl_version = crt_entry->ddl_version;
*dml_version = crt_entry->dml_version;
return;
}
if (!local_mdvsn->nuke_happened)
{
/* TODO gcaragea 6/3/2014: Traverse subtransaction contexts during look-up (MPP-22935) */
mdver_request_from_global(key, ddl_version, dml_version);
}
else
{
mdver_request_after_nuke(key, ddl_version, dml_version);
}
Assert(INVALID_MD_VERSION != *ddl_version ||
INVALID_MD_VERSION != *dml_version);
mdver_entry new_entry = { key, *ddl_version, *dml_version};
mdver_local_mdvsn_add(local_mdvsn, &new_entry, true /* local */);
}
/*
* 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) */
}
}
}
