/* attach worker to the shared memory segment, read the job structure */
static void
initialize_worker(uint32 segment)
{
dsm_segment *seg;
ResourceOwner old,
tmp;
/* Connect to dynamic shared memory segment.
*
* In order to attach a dynamic shared memory segment, we need a
* resource owner. We cannot to StartTransactionCommand here, since
* we haven't yet attached to the database: to do this, we need to
* fetch information about connection properties from the shared
* memory segment.
*/
old = CurrentResourceOwner;
CurrentResourceOwner = ResourceOwnerCreate(NULL, "Background Worker");
seg = dsm_attach(segment);
if (seg == NULL)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("unable to map dynamic shared memory segment")));
dsm_pin_mapping(seg);
tmp = CurrentResourceOwner;
CurrentResourceOwner = old;
ResourceOwnerDelete(tmp);
job = palloc(sizeof(JobDesc));
/* copy the arguments from shared memory segment */
memcpy(job, dsm_segment_address(seg), sizeof(JobDesc));
/* and detach it right away */
dsm_detach(seg);
Assert(job->magic == JOB_MAGIC);
job_run_function.schema = quote_identifier(job->schemaname);
job_run_function.name = quote_identifier("run_job");
}
/*
* Initialize dsm segment. Returns true if new segment was created and
* false if attached to existing segment
*/
bool
init_dsm_segment(size_t blocks_count, size_t block_size)
{
bool ret;
/* if there is already an existing segment then attach to it */
if (dsm_cfg->segment_handle != 0)
{
ret = false;
segment = dsm_attach(dsm_cfg->segment_handle);
}
/*
* If segment hasn't been created yet or has already been destroyed
* (it happens when last session detaches segment) then create new one
*/
if (dsm_cfg->segment_handle == 0 || segment == NULL)
{
/* create segment */
segment = dsm_create(block_size * blocks_count, 0);
dsm_cfg->segment_handle = dsm_segment_handle(segment);
dsm_cfg->first_free = 0;
dsm_cfg->block_size = block_size;
dsm_cfg->blocks_count = blocks_count;
init_dsm_table(block_size, 0, dsm_cfg->blocks_count);
ret = true;
}
/*
* Keep mapping till the end of the session. Otherwise it would be
* destroyed by the end of transaction
*/
dsm_pin_mapping(segment);
return ret;
}
