worker.bgw_start_time=BgWorkerStart_RecoveryFinished;

worker.bgw_restart_time=BGW_NEVER_RESTART;

worker.bgw_main=worker_spi_main;

worker.bgw_sighup=NULL;

worker.bgw_sigterm=NULL;

worker.bgw_main=NULL;/* new worker might not have library loaded */

sprintf(worker.bgw_library_name,"worker_spi");

sprintf(worker.bgw_function_name,"worker_spi_main");

worker.bgw_sighup=NULL;/* new worker might not have library loaded */

worker.bgw_sigterm=NULL;/* new worker might not have library loaded */

snprintf(worker.bgw_name,BGW_MAXLEN,"worker %d",i);

worker.bgw_main_arg=Int32GetDatum(i);

The structure <structname>BackgroundWorker</structname> is defined thus:

<programlisting>

typedef void (*bgworker_main_type)(void *main_arg);

typedef void (*bgworker_sighdlr_type)(SIGNAL_ARGS);

typedef struct BackgroundWorker

{

char bgw_name[BGW_MAXLEN];

char bgw_library_name[BGW_MAXLEN]; /* only if bgw_main is NULL */

char bgw_function_name[BGW_MAXLEN]; /* only if bgw_main is NULL */

Datum bgw_main_arg;

bgworker_sighdlr_type bgw_sighup;

bgworker_sighdlr_type bgw_sigterm;

} BackgroundWorker;

</programlisting>

</para>

<structfield>bgw_main</structfield> is NULL.

</para>

<para>

<structfield>bgw_sighup</structfield> and <structfield>bgw_sigterm</> are

pointers to functions that will be installed as signal handlers for the new

process. If <structfield>bgw_sighup</> is NULL, then <literal>SIG_IGN</>

is used; if <structfield>bgw_sigterm</> is NULL, a handler is installed that

will terminate the process after logging a suitable message. These

fields should not be used if <structfield>bgw_main</> is NULL; instead,

the worker process should set its own signal handlers before calling

<function>BackgroundWorkerUnblockSignals()</function>.

</para>

<para>Once running, the process can connect to a database by calling

<function>BackgroundWorkerInitializeConnection(<parameter>char *dbname</parameter>, <parameter>char *username</parameter>)</function>.

This allows the process to run transactions and queries using the

<para>

Signals are initially blocked when control reaches the

<structfield>bgw_main</> function, and must be unblocked by it; this is to

allow the process tofurthercustomize its signal handlers, if necessary.

allow the process to customize its signal handlers, if necessary.

Signals can be unblocked in the new process by calling

<function>BackgroundWorkerUnblockSignals</> and blocked by calling

<function>BackgroundWorkerBlockSignals</>.

rw->rw_worker.bgw_restart_time=slot->worker.bgw_restart_time;

rw->rw_worker.bgw_main=slot->worker.bgw_main;

rw->rw_worker.bgw_main_arg=slot->worker.bgw_main_arg;

rw->rw_worker.bgw_sighup=slot->worker.bgw_sighup;

rw->rw_worker.bgw_sigterm=slot->worker.bgw_sigterm;

rw->rw_backend=NULL;

pqsignal(SIGUSR1,bgworker_sigusr1_handler);

pqsignal(SIGFPE,SIG_IGN);

}

if (worker->bgw_sigterm)

pqsignal(SIGTERM,worker->bgw_sigterm);

pqsignal(SIGTERM,bgworker_die);

if (worker->bgw_sighup)

pqsignal(SIGHUP,worker->bgw_sighup);

pqsignal(SIGHUP,SIG_IGN);

pqsignal(SIGTERM,bgworker_die);

pqsignal(SIGHUP,SIG_IGN);

pqsignal(SIGQUIT,bgworker_quickdie);

InitializeTimeouts();/* establishes SIGALRM handler */

typedefvoid (*bgworker_main_type) (Datummain_arg);

typedefvoid (*bgworker_sighdlr_type) (SIGNAL_ARGS);

charbgw_library_name[BGW_MAXLEN];/* only if bgw_main is NULL */

charbgw_function_name[BGW_MAXLEN];/* only if bgw_main is NULL */

Datumbgw_main_arg;

bgworker_sighdlr_typebgw_sighup;

bgworker_sighdlr_typebgw_sigterm;

}BackgroundWorker;