functions.c

PostgreSQL7.4.6 for Linux

	else
		paramLI = (ParamListInfo) NULL;

	if (fcache->paramLI)
		pfree(fcache->paramLI);

	fcache->paramLI = paramLI;
}

static TupleTableSlot *
copy_function_result(SQLFunctionCachePtr fcache,
					 TupleTableSlot *resultSlot)
{
	TupleTableSlot *funcSlot;
	TupleDesc	resultTd;
	HeapTuple	resultTuple;
	HeapTuple	newTuple;

	Assert(!TupIsNull(resultSlot));
	resultTuple = resultSlot->val;

	funcSlot = fcache->funcSlot;

	if (funcSlot == NULL)
		return resultSlot;		/* no need to copy result */

	/*
	 * If first time through, we have to initialize the funcSlot's tuple
	 * descriptor.
	 */
	if (funcSlot->ttc_tupleDescriptor == NULL)
	{
		resultTd = CreateTupleDescCopy(resultSlot->ttc_tupleDescriptor);
		ExecSetSlotDescriptor(funcSlot, resultTd, true);
		ExecSetSlotDescriptorIsNew(funcSlot, true);
	}

	newTuple = heap_copytuple(resultTuple);

	return ExecStoreTuple(newTuple, funcSlot, InvalidBuffer, true);
}

static Datum
postquel_execute(execution_state *es,
				 FunctionCallInfo fcinfo,
				 SQLFunctionCachePtr fcache)
{
	TupleTableSlot *slot;
	Datum		value;

	if (es->status == F_EXEC_START)
		postquel_start(es, fcache);

	slot = postquel_getnext(es);

	if (TupIsNull(slot))
	{
		postquel_end(es);
		fcinfo->isnull = true;

		/*
		 * If this isn't the last command for the function we have to
		 * increment the command counter so that subsequent commands can
		 * see changes made by previous ones.
		 */
		if (!LAST_POSTQUEL_COMMAND(es))
			CommandCounterIncrement();
		return (Datum) NULL;
	}

	if (LAST_POSTQUEL_COMMAND(es))
	{
		TupleTableSlot *resSlot;

		/*
		 * Copy the result.  copy_function_result is smart enough to do
		 * nothing when no action is called for.  This helps reduce the
		 * logic and code redundancy here.
		 */
		resSlot = copy_function_result(fcache, slot);

		/*
		 * If we are supposed to return a tuple, we return the tuple slot
		 * pointer converted to Datum.	If we are supposed to return a
		 * simple value, then project out the first attribute of the
		 * result tuple (ie, take the first result column of the final
		 * SELECT).
		 */
		if (fcache->returnsTuple)
		{
			/*
			 * XXX do we need to remove junk attrs from the result tuple?
			 * Probably OK to leave them, as long as they are at the end.
			 */
			value = PointerGetDatum(resSlot);
			fcinfo->isnull = false;
		}
		else
		{
			value = heap_getattr(resSlot->val,
								 1,
								 resSlot->ttc_tupleDescriptor,
								 &(fcinfo->isnull));

			/*
			 * Note: if result type is pass-by-reference then we are
			 * returning a pointer into the tuple copied by
			 * copy_function_result.  This is OK.
			 */
		}

		/*
		 * If this is a single valued function we have to end the function
		 * execution now.
		 */
		if (!fcinfo->flinfo->fn_retset)
			postquel_end(es);

		return value;
	}

	/*
	 * If this isn't the last command for the function, we don't return
	 * any results, but we have to increment the command counter so that
	 * subsequent commands can see changes made by previous ones.
	 */
	CommandCounterIncrement();
	return (Datum) NULL;
}

Datum
fmgr_sql(PG_FUNCTION_ARGS)
{
	MemoryContext oldcontext;
	SQLFunctionCachePtr fcache;
	ErrorContextCallback sqlerrcontext;
	execution_state *es;
	Datum		result = 0;

	/*
	 * Switch to context in which the fcache lives.  This ensures that
	 * parsetrees, plans, etc, will have sufficient lifetime.  The
	 * sub-executor is responsible for deleting per-tuple information.
	 */
	oldcontext = MemoryContextSwitchTo(fcinfo->flinfo->fn_mcxt);

	/*
	 * Setup error traceback support for ereport()
	 */
	sqlerrcontext.callback = sql_exec_error_callback;
	sqlerrcontext.arg = fcinfo->flinfo;
	sqlerrcontext.previous = error_context_stack;
	error_context_stack = &sqlerrcontext;

	/*
	 * Initialize fcache (build plans) if first time through.
	 */
	fcache = (SQLFunctionCachePtr) fcinfo->flinfo->fn_extra;
	if (fcache == NULL)
	{
		init_sql_fcache(fcinfo->flinfo);
		fcache = (SQLFunctionCachePtr) fcinfo->flinfo->fn_extra;
	}
	es = fcache->func_state;

	/*
	 * Convert params to appropriate format if starting a fresh execution.
	 * (If continuing execution, we can re-use prior params.)
	 */
	if (es && es->status == F_EXEC_START)
		postquel_sub_params(fcache, fcinfo);

	/*
	 * Find first unfinished query in function.
	 */
	while (es && es->status == F_EXEC_DONE)
		es = es->next;

	/*
	 * Execute each command in the function one after another until we're
	 * executing the final command and get a result or we run out of
	 * commands.
	 */
	while (es)
	{
		result = postquel_execute(es, fcinfo, fcache);
		if (es->status != F_EXEC_DONE)
			break;
		es = es->next;
	}

	/*
	 * If we've gone through every command in this function, we are done.
	 */
	if (es == (execution_state *) NULL)
	{
		/*
		 * Reset the execution states to start over again on next call.
		 */
		es = fcache->func_state;
		while (es)
		{
			es->status = F_EXEC_START;
			es = es->next;
		}

		/*
		 * Let caller know we're finished.
		 */
		if (fcinfo->flinfo->fn_retset)
		{
			ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;

			if (rsi && IsA(rsi, ReturnSetInfo))
				rsi->isDone = ExprEndResult;
			else
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("set-valued function called in context that cannot accept a set")));
			fcinfo->isnull = true;
			result = (Datum) 0;

			/* Deregister shutdown callback, if we made one */
			if (fcache->shutdown_reg)
			{
				UnregisterExprContextCallback(rsi->econtext,
											  ShutdownSQLFunction,
											  PointerGetDatum(fcache));
				fcache->shutdown_reg = false;
			}
		}

		error_context_stack = sqlerrcontext.previous;

		MemoryContextSwitchTo(oldcontext);

		return result;
	}

	/*
	 * If we got a result from a command within the function it has to be
	 * the final command.  All others shouldn't be returning anything.
	 */
	Assert(LAST_POSTQUEL_COMMAND(es));

	/*
	 * Let caller know we're not finished.
	 */
	if (fcinfo->flinfo->fn_retset)
	{
		ReturnSetInfo *rsi = (ReturnSetInfo *) fcinfo->resultinfo;

		if (rsi && IsA(rsi, ReturnSetInfo))
			rsi->isDone = ExprMultipleResult;
		else
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("set-valued function called in context that cannot accept a set")));

		/*
		 * Ensure we will get shut down cleanly if the exprcontext is not
		 * run to completion.
		 */
		if (!fcache->shutdown_reg)
		{
			RegisterExprContextCallback(rsi->econtext,
										ShutdownSQLFunction,
										PointerGetDatum(fcache));
			fcache->shutdown_reg = true;
		}
	}

	error_context_stack = sqlerrcontext.previous;

	MemoryContextSwitchTo(oldcontext);

	return result;
}


/*
 * error context callback to let us supply a call-stack traceback
 */
static void
sql_exec_error_callback(void *arg)
{
	FmgrInfo   *flinfo = (FmgrInfo *) arg;
	SQLFunctionCachePtr fcache = (SQLFunctionCachePtr) flinfo->fn_extra;
	char	   *fn_name;

	fn_name = get_func_name(flinfo->fn_oid);
	/* safety check, shouldn't happen */
	if (fn_name == NULL)
		return;

	/*
	 * Try to determine where in the function we failed.  If there is a
	 * query with non-null QueryDesc, finger it.  (We check this rather
	 * than looking for F_EXEC_RUN state, so that errors during
	 * ExecutorStart or ExecutorEnd are blamed on the appropriate query;
	 * see postquel_start and postquel_end.)
	 */
	if (fcache)
	{
		execution_state *es;
		int			query_num;

		es = fcache->func_state;
		query_num = 1;
		while (es)
		{
			if (es->qd)
			{
				errcontext("SQL function \"%s\" statement %d",
						   fn_name, query_num);
				break;
			}
			es = es->next;
			query_num++;
		}
		if (es == NULL)
		{
			/*
			 * couldn't identify a running query; might be function entry,
			 * function exit, or between queries.
			 */
			errcontext("SQL function \"%s\"", fn_name);
		}
	}
	else
	{
		/* must have failed during init_sql_fcache() */
		errcontext("SQL function \"%s\" during startup", fn_name);
	}

	/* free result of get_func_name (in case this is only a notice) */
	pfree(fn_name);
}


/*
 * callback function in case a function-returning-set needs to be shut down
 * before it has been run to completion
 */
static void
ShutdownSQLFunction(Datum arg)
{
	SQLFunctionCachePtr fcache = (SQLFunctionCachePtr) DatumGetPointer(arg);
	execution_state *es = fcache->func_state;

	while (es != NULL)
	{
		/* Shut down anything still running */
		if (es->status == F_EXEC_RUN)
			postquel_end(es);
		/* Reset states to START in case we're called again */
		es->status = F_EXEC_START;
		es = es->next;
	}

	/* execUtils will deregister the callback... */
	fcache->shutdown_reg = false;
}