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Use fast path in plpgsql's RETURN/RETURN NEXT in more cases. 

exec_stmt_return() and exec_stmt_return_next() have fast-path code for
handling a simple variable reference (i.e. "return var") without going
through the full expression evaluation machinery.  For some reason,
pl_gram.y was under the impression that this fast path only applied for
record/row variables; but in reality code for handling regular scalar
variables has been there all along.  Adjusting the logic to allow that
code to be used actually results in a net savings of code in pl_gram.y
(by eliminating some redundancy), and it buys a measurable though not
very impressive amount of speedup.

Noted while fooling with my expanded-array patch, wherein this makes a much
bigger difference because it enables returning an expanded array variable
without an extra flattening step.  But AFAICS this is a win regardless,
so commit it separately.
This commit is contained in:
Tom Lane 2015-02-16 15:28:40 -05:00
parent 2c75531a6c
commit 9e3ad1aac5
2 changed files with 28 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
src/pl/plpgsql/src/pl_exec.c
View File

@ -2452,8 +2452,9 @@ exec_stmt_return(PLpgSQL_execstate *estate, PLpgSQL_stmt_return *stmt)
estate->retisnull = true;
/*
* This special-case path covers record/row variables in fn_retistuple
* functions, as well as functions with one or more OUT parameters.
* Special case path when the RETURN expression is a simple variable
* reference; in particular, this path is always taken in functions with
* one or more OUT parameters.
*/
if (stmt->retvarno >= 0)
{
@ -2576,8 +2577,9 @@ exec_stmt_return_next(PLpgSQL_execstate *estate,
natts = tupdesc->natts;
/*
* This special-case path covers record/row variables in fn_retistuple
* functions, as well as functions with one or more OUT parameters.
* Special case path when the RETURN NEXT expression is a simple variable
* reference; in particular, this path is always taken in functions with
* one or more OUT parameters.
*/
if (stmt->retvarno >= 0)
{

42
src/pl/plpgsql/src/pl_gram.y
View File

@ -3036,16 +3036,17 @@ make_return_stmt(int location)
errmsg("RETURN cannot have a parameter in function returning void"),
parser_errposition(yylloc)));
}
else if (plpgsql_curr_compile->fn_retistuple)
else
{
/*
* We want to special-case simple row or record references for
* efficiency. So peek ahead to see if that's what we have.
* We want to special-case simple variable references for efficiency.
* So peek ahead to see if that's what we have.
*/
int tok = yylex();
if (tok == T_DATUM && plpgsql_peek() == ';' &&
(yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_ROW ||
(yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_VAR ||
yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_ROW ||
yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_REC))
{
new->retvarno = yylval.wdatum.datum->dno;
@ -3055,19 +3056,16 @@ make_return_stmt(int location)
}
else
{
/* Not (just) a row/record name, so treat as expression */
/*
* Not (just) a variable name, so treat as expression.
*
* Note that a well-formed expression is _required_ here;
* anything else is a compile-time error.
*/
plpgsql_push_back_token(tok);
new->expr = read_sql_expression(';', ";");
}
}
else
{
/*
* Note that a well-formed expression is _required_ here;
* anything else is a compile-time error.
*/
new->expr = read_sql_expression(';', ";");
}
return (PLpgSQL_stmt *) new;
}
@ -3099,16 +3097,17 @@ make_return_next_stmt(int location)
parser_errposition(yylloc)));
new->retvarno = plpgsql_curr_compile->out_param_varno;
}
else if (plpgsql_curr_compile->fn_retistuple)
else
{
/*
* We want to special-case simple row or record references for
* efficiency. So peek ahead to see if that's what we have.
* We want to special-case simple variable references for efficiency.
* So peek ahead to see if that's what we have.
*/
int tok = yylex();
if (tok == T_DATUM && plpgsql_peek() == ';' &&
(yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_ROW ||
(yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_VAR ||
yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_ROW ||
yylval.wdatum.datum->dtype == PLPGSQL_DTYPE_REC))
{
new->retvarno = yylval.wdatum.datum->dno;
@ -3118,13 +3117,16 @@ make_return_next_stmt(int location)
}
else
{
/* Not (just) a row/record name, so treat as expression */
/*
* Not (just) a variable name, so treat as expression.
*
* Note that a well-formed expression is _required_ here;
* anything else is a compile-time error.
*/
plpgsql_push_back_token(tok);
new->expr = read_sql_expression(';', ";");
}
}
else
new->expr = read_sql_expression(';', ";");
return (PLpgSQL_stmt *) new;
}