pl_exec.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

	 * Determine if we assign to a record or a row
	 */
	if (stmt->rec != NULL)
		rec = (PLpgSQL_rec *) (estate->datums[stmt->rec->recno]);
	else if (stmt->row != NULL)
		row = (PLpgSQL_row *) (estate->datums[stmt->row->rowno]);
	else
		elog(ERROR, "unsupported target");

	/*
	 * Open the implicit cursor for the statement and fetch the initial 10
	 * rows.
	 */
	exec_run_select(estate, stmt->query, 0, &portal);

	SPI_cursor_fetch(portal, true, 10);
	tuptab = SPI_tuptable;
	n = SPI_processed;

	/*
	 * If the query didn't return any rows, set the target to NULL and return
	 * with FOUND = false.
	 */
	if (n == 0)
		exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
	else
		found = true;			/* processed at least one tuple */

	/*
	 * Now do the loop
	 */
	while (n > 0)
	{
		for (i = 0; i < n; i++)
		{
			/*
			 * Assign the tuple to the target
			 */
			exec_move_row(estate, rec, row, tuptab->vals[i], tuptab->tupdesc);

			/*
			 * Execute the statements
			 */
			rc = exec_stmts(estate, stmt->body);
			if (rc != PLPGSQL_RC_OK)
			{
				if (rc == PLPGSQL_RC_EXIT)
				{
					if (estate->exitlabel == NULL)
						/* unlabelled exit, finish the current loop */
						rc = PLPGSQL_RC_OK;
					else if (stmt->label != NULL &&
							 strcmp(stmt->label, estate->exitlabel) == 0)
					{
						/* labelled exit, matches the current stmt's label */
						estate->exitlabel = NULL;
						rc = PLPGSQL_RC_OK;
					}

					/*
					 * otherwise, we processed a labelled exit that does not
					 * match the current statement's label, if any: return
					 * RC_EXIT so that the EXIT continues to recurse upward.
					 */
				}
				else if (rc == PLPGSQL_RC_CONTINUE)
				{
					if (estate->exitlabel == NULL)
					{
						/* anonymous continue, so re-run the current loop */
						rc = PLPGSQL_RC_OK;
						continue;
					}
					else if (stmt->label != NULL &&
							 strcmp(stmt->label, estate->exitlabel) == 0)
					{
						/* label matches named continue, so re-run loop */
						rc = PLPGSQL_RC_OK;
						estate->exitlabel = NULL;
						continue;
					}

					/*
					 * otherwise, we processed a named continue that does not
					 * match the current statement's label, if any: return
					 * RC_CONTINUE so that the CONTINUE will propagate up the
					 * stack.
					 */
				}

				/*
				 * We're aborting the loop, so cleanup and set FOUND. (This
				 * code should match the code after the loop.)
				 */
				SPI_freetuptable(tuptab);
				SPI_cursor_close(portal);
				exec_set_found(estate, found);

				return rc;
			}
		}

		SPI_freetuptable(tuptab);

		/*
		 * Fetch the next 50 tuples
		 */
		SPI_cursor_fetch(portal, true, 50);
		n = SPI_processed;
		tuptab = SPI_tuptable;
	}

	/*
	 * Release last group of tuples
	 */
	SPI_freetuptable(tuptab);

	/*
	 * Close the implicit cursor
	 */
	SPI_cursor_close(portal);

	/*
	 * Set the FOUND variable to indicate the result of executing the loop
	 * (namely, whether we looped one or more times). This must be set here so
	 * that it does not interfere with the value of the FOUND variable inside
	 * the loop processing itself.
	 */
	exec_set_found(estate, found);

	return rc;
}


/* ----------
 * exec_stmt_select			Run a query and assign the first
 *					row to a record or rowtype.
 * ----------
 */
static int
exec_stmt_select(PLpgSQL_execstate *estate, PLpgSQL_stmt_select *stmt)
{
	PLpgSQL_rec *rec = NULL;
	PLpgSQL_row *row = NULL;
	SPITupleTable *tuptab;
	uint32		n;

	/*
	 * Initialize the global found variable to false
	 */
	exec_set_found(estate, false);

	/*
	 * Determine if we assign to a record or a row
	 */
	if (stmt->rec != NULL)
		rec = (PLpgSQL_rec *) (estate->datums[stmt->rec->recno]);
	else if (stmt->row != NULL)
		row = (PLpgSQL_row *) (estate->datums[stmt->row->rowno]);
	else
		elog(ERROR, "unsupported target");

	/*
	 * Run the query
	 */
	exec_run_select(estate, stmt->query, 1, NULL);
	tuptab = estate->eval_tuptable;
	n = estate->eval_processed;

	/*
	 * If the query didn't return any rows, set the target to NULL and return.
	 */
	if (n == 0)
	{
		exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
		exec_eval_cleanup(estate);
		return PLPGSQL_RC_OK;
	}

	/*
	 * Put the result into the target and set found to true
	 */
	exec_move_row(estate, rec, row, tuptab->vals[0], tuptab->tupdesc);
	exec_set_found(estate, true);

	exec_eval_cleanup(estate);

	return PLPGSQL_RC_OK;
}


/* ----------
 * exec_stmt_exit			Implements EXIT and CONTINUE
 *
 * This begins the process of exiting / restarting a loop.
 * ----------
 */
static int
exec_stmt_exit(PLpgSQL_execstate *estate, PLpgSQL_stmt_exit *stmt)
{
	/*
	 * If the exit / continue has a condition, evaluate it
	 */
	if (stmt->cond != NULL)
	{
		bool		value;
		bool		isnull;

		value = exec_eval_boolean(estate, stmt->cond, &isnull);
		exec_eval_cleanup(estate);
		if (isnull || value == false)
			return PLPGSQL_RC_OK;
	}

	estate->exitlabel = stmt->label;
	if (stmt->is_exit)
		return PLPGSQL_RC_EXIT;
	else
		return PLPGSQL_RC_CONTINUE;
}


/* ----------
 * exec_stmt_return			Evaluate an expression and start
 *					returning from the function.
 * ----------
 */
static int
exec_stmt_return(PLpgSQL_execstate *estate, PLpgSQL_stmt_return *stmt)
{
	/*
	 * If processing a set-returning PL/PgSQL function, the final RETURN
	 * indicates that the function is finished producing tuples.  The rest of
	 * the work will be done at the top level.
	 */
	if (estate->retisset)
		return PLPGSQL_RC_RETURN;

	/* initialize for null result (possibly a tuple) */
	estate->retval = (Datum) 0;
	estate->rettupdesc = NULL;
	estate->retisnull = true;

	if (stmt->retvarno >= 0)
	{
		PLpgSQL_datum *retvar = estate->datums[stmt->retvarno];

		switch (retvar->dtype)
		{
			case PLPGSQL_DTYPE_VAR:
				{
					PLpgSQL_var *var = (PLpgSQL_var *) retvar;

					estate->retval = var->value;
					estate->retisnull = var->isnull;
					estate->rettype = var->datatype->typoid;
				}
				break;

			case PLPGSQL_DTYPE_REC:
				{
					PLpgSQL_rec *rec = (PLpgSQL_rec *) retvar;

					if (HeapTupleIsValid(rec->tup))
					{
						estate->retval = (Datum) rec->tup;
						estate->rettupdesc = rec->tupdesc;
						estate->retisnull = false;
					}
				}
				break;

			case PLPGSQL_DTYPE_ROW:
				{
					PLpgSQL_row *row = (PLpgSQL_row *) retvar;

					Assert(row->rowtupdesc);
					estate->retval = (Datum) make_tuple_from_row(estate, row,
															row->rowtupdesc);
					if (estate->retval == (Datum) NULL) /* should not happen */
						elog(ERROR, "row not compatible with its own tupdesc");
					estate->rettupdesc = row->rowtupdesc;
					estate->retisnull = false;
				}
				break;

			default:
				elog(ERROR, "unrecognized dtype: %d", retvar->dtype);
		}

		return PLPGSQL_RC_RETURN;
	}

	if (stmt->expr != NULL)
	{
		if (estate->retistuple)
		{
			exec_run_select(estate, stmt->expr, 1, NULL);
			if (estate->eval_processed > 0)
			{
				estate->retval = (Datum) estate->eval_tuptable->vals[0];
				estate->rettupdesc = estate->eval_tuptable->tupdesc;
				estate->retisnull = false;
			}
		}
		else
		{
			/* Normal case for scalar results */
			estate->retval = exec_eval_expr(estate, stmt->expr,
											&(estate->retisnull),
											&(estate->rettype));
		}

		return PLPGSQL_RC_RETURN;
	}

	/*
	 * Special hack for function returning VOID: instead of NULL, return a
	 * non-null VOID value.  This is of dubious importance but is kept for
	 * backwards compatibility.  Note that the only other way to get here is
	 * to have written "RETURN NULL" in a function returning tuple.
	 */
	if (estate->fn_rettype == VOIDOID)
	{
		estate->retval = (Datum) 0;
		estate->retisnull = false;
		estate->rettype = VOIDOID;
	}

	return PLPGSQL_RC_RETURN;
}

/* ----------
 * exec_stmt_return_next		Evaluate an expression and add it to the
 *								list of tuples returned by the current
 *								SRF.
 * ----------
 */
static int
exec_stmt_return_next(PLpgSQL_execstate *estate,
					  PLpgSQL_stmt_return_next *stmt)
{
	TupleDesc	tupdesc;
	int			natts;
	HeapTuple	tuple;
	bool		free_tuple = false;

	if (!estate->retisset)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("cannot use RETURN NEXT in a non-SETOF function")));

	if (estate->tuple_store == NULL)
		exec_init_tuple_store(estate);

	/* rettupdesc will be filled by exec_init_tuple_store */
	tupdesc = estate->rettupdesc;
	natts = tupdesc->natts;

	if (stmt->retvarno >= 0)
	{
		PLpgSQL_datum *retvar = estate->datums[stmt->retvarno];

		switch (retvar->dtype)
		{
			case PLPGSQL_DTYPE_VAR:
				{
					PLpgSQL_var *var = (PLpgSQL_var *) retvar;
					Datum		retval = var->value;
					bool		isNull = var->isnull;

					if (natts != 1)
						ereport(ERROR,
								(errcode(ERRCODE_DATATYPE_MISMATCH),
						errmsg("wrong result type supplied in RETURN NEXT")));

					/* coerce type if needed */
					retval = exec_simple_cast_value(retval,
													var->datatype->typoid,
												 tupdesc->attrs[0]->atttypid,
												tupdesc->attrs[0]->atttypmod,
													isNull);

					tuple = heap_form_tuple(tupdesc, &retval, &isNull);

					free_tuple = true;
				}
				break;

			case PLPGSQL_DTYPE_REC:
				{
					PLpgSQL_rec *rec = (PLpgSQL_rec *) retvar;

					if (!HeapTupleIsValid(rec->tup))
						ereport(ERROR,
						  (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
						   errmsg("record \"%s\" is not assigned yet",
								  rec->refname),
						   errdetail("The tuple structure of a not-yet-assigned record is indeterminate.")));
					if (!compatible_tupdesc(tupdesc, rec->tupdesc))
						ereport(ERROR,
								(errcode(ERRCODE_DATATYPE_MISMATCH),
						errmsg("wrong record type supplied in RETURN NEXT")));
					tuple = rec->tup;
				}
				break;

			case PLPGSQL_DTYPE_ROW:
				{
					PLpgSQL_row *row = (PLpgSQL_row *) retvar;

					tuple = make_tuple_from_row(estate, row, tupdesc);
					if (tuple == NULL)
						ereport(ERROR,
								(errcode(ERRCODE_DATATYPE_MISMATCH),
						errmsg("wrong record type supplied in RETURN NEXT")));
					free_tuple = true;
				}
				break;

			default:
				elog(ERROR, "unrecognized dtype: %d", retvar->dtype);
				tuple = NULL;	/* keep compiler quiet */
				break;
		}
	}
	else if (stmt->expr)
	{
		Datum		retval;
		bool		isNull;
		Oid			rettype;

		if (natts != 1)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("wrong result type supplied in RETURN NEXT")));

		retval = exec_eval_expr(estate,
								stmt->expr,
								&isNull,
								&rettype);

		/* coerce type if needed */
		retval = exec_simple_cast_value(retval,
										rettype,
										tupdesc->attrs[0]->atttypid,
										tupdesc->attrs[0]->atttypmod,
										isNull);

		tuple = heap_form_tuple(tupdesc, &retval, &isNull);

		free_tuple = true;

		exec_eval_cleanup(estate);
	}
	else
	{
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("RETURN NEXT must have a parameter")));
		tuple = NULL;			/* keep compiler quiet */
	}

	if (HeapTupleIsValid(tuple))
	{
		MemoryContext oldcxt;

		oldcxt = MemoryContextSwitchTo(estate->tuple_store_cxt);
		tuplestore_puttuple(estate->tuple_store, tuple);
		MemoryContextSwitchTo(oldcxt);

		if (free_tuple)
			heap_freetuple(tuple);
	}

	return PLPGSQL_RC_OK;
}

static void
exec_init_tuple_store(PLpgSQL_execstate *estate)
{
	ReturnSetInfo *rsi = estate->rsi;
	MemoryContext oldcxt;

	/*
	 * Check caller can handle a set result in the way we want
	 */
	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
		(rsi->allowedModes & SFRM_Materialize) == 0 ||
		rsi->expectedDesc == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that cannot accept a set")));

	estate->tuple_store_cxt = rsi->econtext->ecxt_per_query_memory;

	oldcxt = MemoryContextSwitchTo(estate->tuple_store_cxt);
	estate->tuple_store = tuplestore_begin_heap(true, false, work_mem);
	MemoryContextSwitchTo(oldcxt);

	estate->rettupdesc = rsi->expectedDesc;
}

/* ----------
 * exec_stmt_raise			Build a message and throw it with elog()
 * ----------
 */
static int
exec_stmt_raise(PLpgSQL_execstate *estate, PLpgSQL_stmt_raise *stmt)
{
	char	   *cp;