pl_exec.c

关系型数据库 Postgresql 6.5.2

				/* ----------
				 * This is the field to change. Get it's type
				 * and cast the value we insert to that type.
				 * ----------
				 */
				atttype = SPI_gettypeid(rec->tupdesc, i + 1);
				atttypmod = rec->tupdesc->attrs[i]->atttypmod;
				typetup = SearchSysCacheTuple(TYPOID,
									 ObjectIdGetDatum(atttype), 0, 0, 0);
				if (!HeapTupleIsValid(typetup))
					elog(ERROR, "cache lookup for type %u failed", atttype);
				typeStruct = (Form_pg_type) GETSTRUCT(typetup);
				fmgr_info(typeStruct->typinput, &finfo_input);

				attisnull = *isNull;
				values[i] = exec_cast_value(value, valtype,
						   atttype, &finfo_input, atttypmod, &attisnull);
				if (attisnull)
					nulls[i] = 'n';
				else
					nulls[i] = ' ';
			}

			/* ----------
			 * Now call heap_formtuple() to create a new tuple
			 * that replaces the old one in the record.
			 * ----------
			 */
			nulls[i] = '\0';
			rec->tup = heap_formtuple(rec->tupdesc, values, nulls);
			pfree(values);
			pfree(nulls);

			break;

		default:
			elog(ERROR, "unknown dtype %d in exec_assign_value()",
				 target->dtype);
	}
}


/* ----------
 * exec_eval_expr			Evaluate an expression and return
 *					the result Datum.
 * ----------
 */
static Datum
exec_eval_expr(PLpgSQL_execstate * estate,
			   PLpgSQL_expr * expr,
			   bool *isNull,
			   Oid *rettype)
{
	int			rc;

	/* ----------
	 * If not already done create a plan for this expression
	 * ----------
	 */
	if (expr->plan == NULL)
		exec_prepare_plan(estate, expr);

	/* ----------
	 * If this is a simple expression, bypass SPI and use the
	 * executor directly
	 * ----------
	 */
	if (expr->plan_simple_expr != NULL)
		return exec_eval_simple_expr(estate, expr, isNull, rettype);

	rc = exec_run_select(estate, expr, 2);
	if (rc != SPI_OK_SELECT)
		elog(ERROR, "query \"%s\" didn't return data", expr->query);

	/* ----------
	 * If there are no rows selected, the result is NULL.
	 * ----------
	 */
	if (SPI_processed == 0)
	{
		*isNull = true;
		return (Datum) 0;
	}

	/* ----------
	 * Check that the expression returned one single Datum
	 * ----------
	 */
	if (SPI_processed > 1)
		elog(ERROR, "query \"%s\" didn't return a single value", expr->query);
	if (SPI_tuptable->tupdesc->natts != 1)
		elog(ERROR, "query \"%s\" didn't return a single value", expr->query);

	/* ----------
	 * Return the result and it's type
	 * ----------
	 */
	*rettype = SPI_gettypeid(SPI_tuptable->tupdesc, 1);
	return SPI_getbinval(SPI_tuptable->vals[0], SPI_tuptable->tupdesc, 1, isNull);
}


/* ----------
 * exec_run_select			Execute a select query
 * ----------
 */
static int
exec_run_select(PLpgSQL_execstate * estate,
				PLpgSQL_expr * expr, int maxtuples)
{
	PLpgSQL_var *var;
	PLpgSQL_rec *rec;
	PLpgSQL_recfield *recfield;
	PLpgSQL_trigarg *trigarg;
	int			tgargno;
	Oid			tgargoid;
	int			i;
	Datum	   *values;
	char	   *nulls;
	int			rc;
	int			fno;
	bool		isnull;

	/* ----------
	 * On the first call for this expression generate the plan
	 * ----------
	 */
	if (expr->plan == NULL)
		exec_prepare_plan(estate, expr);

	/* ----------
	 * Now build up the values and nulls arguments for SPI_execp()
	 * ----------
	 */
	values = palloc(sizeof(Datum) * (expr->nparams + 1));
	nulls = palloc(expr->nparams + 1);

	for (i = 0; i < expr->nparams; i++)
	{
		switch (estate->datums[expr->params[i]]->dtype)
		{
			case PLPGSQL_DTYPE_VAR:
				var = (PLpgSQL_var *) (estate->datums[expr->params[i]]);
				values[i] = var->value;
				if (var->isnull)
					nulls[i] = 'n';
				else
					nulls[i] = ' ';
				break;

			case PLPGSQL_DTYPE_RECFIELD:
				recfield = (PLpgSQL_recfield *) (estate->datums[expr->params[i]]);
				rec = (PLpgSQL_rec *) (estate->datums[recfield->recno]);

				if (!HeapTupleIsValid(rec->tup))
					elog(ERROR, "record %s is unassigned yet", rec->refname);
				fno = SPI_fnumber(rec->tupdesc, recfield->fieldname);
				if (fno == SPI_ERROR_NOATTRIBUTE)
					elog(ERROR, "record %s has no field %s", rec->refname, recfield->fieldname);

				if (expr->plan_argtypes[i] != SPI_gettypeid(rec->tupdesc, fno))
					elog(ERROR, "type of %s.%s doesn't match that when preparing the plan", rec->refname, recfield->fieldname);

				values[i] = SPI_getbinval(rec->tup, rec->tupdesc, fno, &isnull);
				if (isnull)
					nulls[i] = 'n';
				else
					nulls[i] = ' ';
				break;

			case PLPGSQL_DTYPE_TRIGARG:
				trigarg = (PLpgSQL_trigarg *) (estate->datums[expr->params[i]]);
				tgargno = (int) exec_eval_expr(estate, trigarg->argnum,
											   &isnull, &tgargoid);
				if (isnull || tgargno < 0 || tgargno >= estate->trig_nargs)
				{
					values[i] = 0;
					nulls[i] = 'n';
				}
				else
				{
					values[i] = estate->trig_argv[tgargno];
					nulls[i] = ' ';
				}
				break;

			default:
				elog(ERROR, "unknown parameter dtype %d in exec_eval_expr()", estate->datums[expr->params[i]]);
		}
	}
	nulls[i] = '\0';

	/* ----------
	 * Execute the query
	 * ----------
	 */
	rc = SPI_execp(expr->plan, values, nulls, maxtuples);
	if (rc != SPI_OK_SELECT)
		elog(ERROR, "query \"%s\" isn't a SELECT", expr->query);
	pfree(values);
	pfree(nulls);

	return rc;
}


/* ----------
 * exec_eval_simple_expr -		Evaluate a simple expression returning
 *								a Datum by directly calling ExecEvalExpr().
 * ----------
 */
static Datum
exec_eval_simple_expr(PLpgSQL_execstate * estate,
					  PLpgSQL_expr * expr,
					  bool *isNull,
					  Oid *rettype)
{
	Datum		retval;
	PLpgSQL_var *var;
	PLpgSQL_rec *rec;
	PLpgSQL_recfield *recfield;
	PLpgSQL_trigarg *trigarg;
	int			tgargno;
	Oid			tgargoid;
	int			fno;
	int			i;
	bool		isnull;
	bool		isdone;
	ExprContext *econtext;
	ParamListInfo paramLI;

	/* ----------
	 * Create a simple expression context to hold the arguments
	 * ----------
	 */
	econtext = makeNode(ExprContext);
	paramLI = (ParamListInfo) palloc((expr->nparams + 1) *
									 sizeof(ParamListInfoData));
	econtext->ecxt_param_list_info = paramLI;

	/* ----------
	 * Put the parameter values into the parameter list info of
	 * the expression context.
	 * ----------
	 */
	for (i = 0; i < expr->nparams; i++, paramLI++)
	{
		paramLI->kind = PARAM_NUM;
		paramLI->id = i + 1;

		switch (estate->datums[expr->params[i]]->dtype)
		{
			case PLPGSQL_DTYPE_VAR:
				var = (PLpgSQL_var *) (estate->datums[expr->params[i]]);
				paramLI->isnull = var->isnull;
				paramLI->value = var->value;
				break;

			case PLPGSQL_DTYPE_RECFIELD:
				recfield = (PLpgSQL_recfield *) (estate->datums[expr->params[i]]);
				rec = (PLpgSQL_rec *) (estate->datums[recfield->recno]);

				if (!HeapTupleIsValid(rec->tup))
					elog(ERROR, "record %s is unassigned yet", rec->refname);
				fno = SPI_fnumber(rec->tupdesc, recfield->fieldname);
				if (fno == SPI_ERROR_NOATTRIBUTE)
					elog(ERROR, "record %s has no field %s", rec->refname, recfield->fieldname);

				if (expr->plan_argtypes[i] != SPI_gettypeid(rec->tupdesc, fno))
					elog(ERROR, "type of %s.%s doesn't match that when preparing the plan", rec->refname, recfield->fieldname);

				paramLI->value = SPI_getbinval(rec->tup, rec->tupdesc, fno, &isnull);
				paramLI->isnull = isnull;
				break;

			case PLPGSQL_DTYPE_TRIGARG:
				trigarg = (PLpgSQL_trigarg *) (estate->datums[expr->params[i]]);
				tgargno = (int) exec_eval_expr(estate, trigarg->argnum,
											   &isnull, &tgargoid);
				if (isnull || tgargno < 0 || tgargno >= estate->trig_nargs)
				{
					paramLI->value = 0;
					paramLI->isnull = TRUE;
				}
				else
				{
					paramLI->value = estate->trig_argv[tgargno];
					paramLI->isnull = FALSE;
				}
				break;

			default:
				elog(ERROR, "unknown parameter dtype %d in exec_eval_simple_expr()", estate->datums[expr->params[i]]->dtype);
		}
	}
	paramLI->kind = PARAM_INVALID;

	/* ----------
	 * Initialize things
	 * ----------
	 */
	*isNull = FALSE;
	*rettype = expr->plan_simple_type;
	isdone = FALSE;

	/* ----------
	 * Clear the function cache
	 * ----------
	 */
	exec_eval_clear_fcache(expr->plan_simple_expr);

	/* ----------
	 * Now call the executor to evaluate the expression
	 * ----------
	 */
	SPI_push();
	retval = ExecEvalExpr(expr->plan_simple_expr,
						  econtext,
						  isNull,
						  &isdone);
	SPI_pop();

	/* ----------
	 * That's it.
	 * ----------
	 */
	return retval;
}


/* ----------
 * exec_move_row			Move one tuples values into a
 *					record or row
 * ----------
 */
static void
exec_move_row(PLpgSQL_execstate * estate,
			  PLpgSQL_rec * rec,
			  PLpgSQL_row * row,
			  HeapTuple tup, TupleDesc tupdesc)
{
	PLpgSQL_var *var;
	int			i;
	Datum		value;
	Oid			valtype;
	bool		isnull;

	/* ----------
	 * Record is simple - just put the tuple and it's descriptor
	 * into the record
	 * ----------
	 */
	if (rec != NULL)
	{
		if (HeapTupleIsValid(tup))
		{
			rec->tup = tup;
			rec->tupdesc = tupdesc;
		}
		else
		{
			rec->tup = NULL;
			rec->tupdesc = NULL;
		}

		return;
	}


	/* ----------
	 * Row is a bit more complicated in that we assign the single
	 * attributes of the query to the variables the row points to.
	 * ----------
	 */
	if (row != NULL)
	{
		if (HeapTupleIsValid(tup))
		{
			if (row->nfields != tupdesc->natts)
			{
				elog(ERROR, "query didn't return correct # of attributes for %s",
					 row->refname);
			}

			for (i = 0; i < row->nfields; i++)
			{
				var = (PLpgSQL_var *) (estate->datums[row->varnos[i]]);

				valtype = SPI_gettypeid(tupdesc, i + 1);
				value = SPI_getbinval(tup, tupdesc, i + 1, &isnull);
				exec_assign_value(estate, estate->datums[row->varnos[i]],
								  value, valtype, &isnull);

			}
		}
		else
		{
			for (i = 0; i < row->nfields; i++)
			{
				bool		nullval = true;

				exec_assign_value(estate, estate->datums[row->varnos[i]],
								  (Datum) 0, 0, &nullval);
			}
		}

		return;
	}

	elog(ERROR, "unsupported target in exec_move_row()");
}


/* ----------
 * exec_cast_value			Cast a value if required
 * ----------
 */
static Datum
exec_cast_value(Datum value, Oid valtype,
				Oid reqtype,
				FmgrInfo *reqinput,
				int16 reqtypmod,
				bool *isnull)
{
	if (!*isnull)
	{
		/* ----------
		 * If the type of the queries return value isn't
		 * that of the variable, convert it.
		 * ----------
		 */
		if (valtype != reqtype || reqtypmod > 0)
		{
			HeapTuple	typetup;
			Form_pg_type typeStruct;
			FmgrInfo	finfo_output;
			char	   *extval;

			typetup = SearchSysCacheTuple(TYPOID,
									 ObjectIdGetDatum(valtype), 0, 0, 0);
			if (!HeapTupleIsValid(typetup))
				elog(ERROR, "cache lookup for type %u failed", valtype);
			typeStruct = (Form_pg_type) GETSTRUCT(typetup);

			fmgr_info(typeStruct->typoutput, &finfo_output);
			extval = (char *) (*fmgr_faddr(&finfo_output)) (value, &isnull, -1);
			value = (Datum) (*fmgr_faddr(reqinput)) (extval, &isnull, reqtypmod);
		}
	}

	return value;
}


/* ----------
 * exec_simple_check_node -		Recursively check if an expression
 *								is made only of simple things we can
 *								hand out directly to ExecEvalExpr()
 *								instead of calling SPI.
 * ----------
 */
static bool
exec_simple_check_node(Node *node)
{
	switch (nodeTag(node))
	{
			case T_Expr:
			{
				Expr	   *expr = (Expr *) node;
				List	   *l;

				switch (expr->opType)
				{
					case OP_EXPR:
					case FUNC_EXPR:
					case OR_EXPR:
					case AND_EXPR:
					case NOT_EXPR:
						break;

					default:
						return FALSE;
				}

				foreach(l, expr->args)
				{
					if (!exec_simple_check_node(lfirst(l)))
						return FALSE;
				}

				return TRUE;
			}

		case T_Param:
			return TRUE;

		case T_Const:
			return TRUE;

		default:
			return FALSE;
	}
}


/* ----------
 * exec_simple_check_plan -		Check if a plan is simple enough to
 *								be evaluated by ExecEvalExpr() instead
 *								of SPI.
 * ----------
 */
static void
exec_simple_check_plan(PLpgSQL_expr * expr)
{
	_SPI_plan  *spi_plan = (_SPI_plan *) expr->plan;
	Plan	   *plan;
	TargetEntry *tle;

	expr->plan_simple_expr = NULL;

	/* ----------
	 * 1. We can only evaluate queries that resulted in one single
	 *	  execution plan
	 * ----------
	 */
	if (length(spi_plan->ptlist) != 1)
		return;

	plan = (Plan *) lfirst(spi_plan->ptlist);

	/* ----------
	 * 2. It must be a RESULT plan --> no scan's required
	 * ----------
	 */
	if (plan == NULL)			/* utility statement produces this */
		return;

	if (nodeTag(plan) != T_Result)
		return;

	/* ----------
	 * 3. The plan must have a single attribute as result
	 * ----------
	 */
	if (length(plan->targetlist) != 1)
		return;

	/* ----------
	 * 4. Don't know if all these can break us, so let SPI handle
	 *	  those plans
	 * ----------
	 */
	if (plan->qual != NULL || plan->lefttree != NULL || plan->righttree != NULL)
		return;

	/* ----------
	 * 5. Check that all the nodes in the expression are one of
	 *	  Expr, Param or Const.
	 * ----------
	 */
	tle = (TargetEntry *) lfirst(plan->targetlist);
	if (!exec_simple_check_node(tle->expr))
		return;

	/* ----------
	 * Yes - this is a simple expression. Remember the expression
	 * and the return type
	 * ----------
	 */
	expr->plan_simple_expr = tle->expr;

	switch (nodeTag(tle->expr))
	{
		case T_Expr:
			expr->plan_simple_type =
				((Expr *) (tle->expr))->typeOid;
			break;

		case T_Param:
			expr->plan_simple_type =
				((Param *) (tle->expr))->paramtype;
			break;

		case T_Const:
			expr->plan_simple_type = ((Const *) (tle->expr))->consttype;
			break;

		default:
			expr->plan_simple_type = InvalidOid;
	}

	return;
}


/* ----------
 * exec_eval_clear_fcache -		The function cache is palloc()'d by
 *								the executor, and contains call specific
 *								data based on the arguments. This has
 *								to be recalculated.
 * ----------
 */
static void
exec_eval_clear_fcache(Node *node)
{
	Expr	   *expr;
	List	   *l;

	if (nodeTag(node) != T_Expr)
		return;

	expr = (Expr *) node;

	switch (expr->opType)
	{
		case OP_EXPR:
			((Oper *) (expr->oper))->op_fcache = NULL;
			break;

		case FUNC_EXPR:
			((Func *) (expr->oper))->func_fcache = NULL;
			break;

		default:
			break;
	}

	foreach(l, expr->args)
		exec_eval_clear_fcache(lfirst(l));
}


/* ----------
 * exec_set_found			Set the global found variable
 *					to true/false
 * ----------
 */
static void
exec_set_found(PLpgSQL_execstate * estate, bool state)
{
	PLpgSQL_var *var;

	var = (PLpgSQL_var *) (estate->datums[estate->found_varno]);
	var->value = (Datum) state;
	var->isnull = false;
}