review: Reduce palloc's in numeric operations - Mailing list pgsql-hackers

Hello all

I tested this patch and I can confirm, so this patch can increase
speed about 16-22% (depends on IO waits, load type).

I tested real query (anonymyzed)

SELECT SUM(COALESCE((a * b * c * (d + ((1 -(d)) * (1 -(e))))),0)) m1 FROM  tab;

-- patched
4493     26.5591  postgres                 slot_deform_tuple
1327      7.8442  postgres                 AllocSetAlloc
1313      7.7614  postgres                 ExecMakeFunctionResultNoSets
1105      6.5319  postgres                 set_var_from_num_nocopy
924       5.4620  postgres                 make_result
637       3.7654  postgres                 mul_var
635       3.7536  postgres                 numeric_mul
560       3.3103  postgres                 MemoryContextAlloc
405       2.3940  postgres                 AllocSetFree
389       2.2995  postgres                 ExecEvalScalarVarFast
332       1.9625  postgres                 slot_getsomeattrs
322       1.9034  postgres                 numeric_add
313       1.8502  postgres                 add_abs
304       1.7970  postgres                 pfree
238       1.4069  postgres                 slot_getattr
216       1.2768  postgres                 numeric_sub
200       1.1822  postgres                 heap_tuple_untoast_attr
183       1.0818  postgres                 strip_var
180       1.0640  postgres                 ExecEvalConst
173       1.0226  postgres                 alloc_var
172       1.0167  postgres                 check_stack_depth

-- origin
4419     22.8325  postgres                 slot_deform_tuple
2041     10.5456  postgres                 AllocSetAlloc
1248      6.4483  postgres                 set_var_from_num
1186      6.1279  postgres                 ExecMakeFunctionResultNoSets
886       4.5779  postgres                 MemoryContextAlloc
856       4.4229  postgres                 make_result
757       3.9113  postgres                 numeric_mul
731       3.7770  postgres                 AllocSetFree
625       3.2293  postgres                 mul_var
601       3.1053  postgres                 alloc_var
545       2.8160  postgres                 pfree
503       2.5989  postgres                 free_var
458       2.3664  postgres                 slot_getsomeattrs
378       1.9531  postgres                 numeric_add
360       1.8601  postgres                 add_abs
336       1.7361  postgres                 ExecEvalScalarVarFast
266       1.3744  postgres                 slot_getattr
221       1.1419  postgres                 numeric_sub

Review:

1) this patch was clearly applied and compilation was without warning

2) regress tests -  All 133 tests passed.

4) don't see any memory leaks there (verified by following code)

CREATE OR REPLACE FUNCTION public.fx(_m integer)RETURNS voidLANGUAGE plpgsql
AS $function$
declare m numeric = 10;       n numeric = 20022.222; r numeric;
begin for i in 1.._m loop   r := m * n; end loop;
end;
$function$


postgres=# select fx(10000000);fx
----

(1 row)

Time: 5312.623 ms  --- original ( 4798.103 ms -- patched  10% speedup)

5) it respect PostgreSQL's coding standards

6) we would to accept this patch - it can carry 10% speedup
calculations with numerics.

Regards

Pavel Stehule