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improve the performance of computing the square root of numeric.

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before optimization:
openGauss=# explain analyse select sqrt(t0) from t_numeric limit 10000000;
                                                          QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.00..292129.20 rows=8468656 width=5) (actual time=4.152..170690.136 rows=8388608 loops=1)
   ->  Seq Scan on t_numeric  (cost=0.00..292129.20 rows=8468656 width=5) (actual time=4.150..169250.862 rows=8388608 loops=1)
 Total runtime: 171767.268 ms
(3 rows)

Time: 171768.179 ms

after optimization:
openGauss=#  explain analyse select sqrt(t0) from t_numeric limit 10000000;
                                                          QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.00..292129.20 rows=8468656 width=5) (actual time=3.850..129299.312 rows=8388608 loops=1)
   ->  Seq Scan on t_numeric  (cost=0.00..292129.20 rows=8468656 width=5) (actual time=3.848..127801.242 rows=8388608 loops=1)
 Total runtime: 130378.841 ms
(3 rows)

Time: 130379.709 ms
This commit is contained in:
junhangis
2022-07-26 21:57:58 +08:00
parent 812f586beb
commit 0c5e9903ce
1 changed files with 38 additions and 9 deletions
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47
src/common/backend/utils/adt/numeric.cpp
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@ -154,6 +154,7 @@ static void zero_var(NumericVar* var);
static const char* set_var_from_str(const char* str, const char* cp, NumericVar* dest);
static void set_var_from_num(Numeric value, NumericVar* dest);
static void set_var_from_var(const NumericVar* value, NumericVar* dest);
static void init_var_from_var(const NumericVar *value, NumericVar *dest);
static char* get_str_from_var(NumericVar* var);
static char* get_str_from_var_sci(NumericVar* var, int rscale);
@ -2594,7 +2595,7 @@ Datum numeric_sqrt(PG_FUNCTION_ARGS)
*/
init_var_from_num(num, &arg);
init_var(&result);
quick_init_var(&result);
/* Assume the input was normalized, so arg.weight is accurate */
sweight = (arg.weight + 1) * DEC_DIGITS / 2 - 1;
@ -4165,6 +4166,27 @@ static void set_var_from_var(const NumericVar* value, NumericVar* dest)
dest->digits = newbuf + 1;
}
/*
* init_var_from_var() -
*
* init one variable from another - they must NOT be the same variable
*/
static void
init_var_from_var(const NumericVar *value, NumericVar *dest)
{
init_alloc_var(dest, value->ndigits);
dest->weight = value->weight;
dest->sign = value->sign;
dest->dscale = value->dscale;
errno_t rc = memcpy_s(dest->digits,
value->ndigits * sizeof(NumericDigit),
value->digits,
value->ndigits * sizeof(NumericDigit));
securec_check(rc, "\0", "\0");
}
static void remove_tail_zero(char *ascii)
{
if (!HIDE_TAILING_ZERO || ascii == NULL) {
@ -5482,6 +5504,7 @@ static void div_var_fast(NumericVar* var1, NumericVar* var2, NumericVar* result,
int var2ndigits = var2->ndigits;
NumericDigit* var1digits = var1->digits;
NumericDigit* var2digits = var2->digits;
int tdiv[NUMERIC_LOCAL_NDIG];
/*
* First of all division by zero check; we must not be handed an
@ -5529,7 +5552,14 @@ static void div_var_fast(NumericVar* var1, NumericVar* var2, NumericVar* result,
* position of dividend space. A final pass of carry propagation takes
* care of any mistaken quotient digits.
*/
div = (int*)palloc0((div_ndigits + 1) * sizeof(int));
i = (div_ndigits + 1) * sizeof(int);
if (div_ndigits > NUMERIC_LOCAL_NMAX) {
div = (int *) palloc0(i);
} else {
errno_t rc = memset_s(tdiv, i, 0, i);
securec_check(rc, "\0", "\0");
div = tdiv;
}
for (i = 0; i < var1ndigits; i++)
div[i + 1] = var1digits[i];
@ -5672,7 +5702,9 @@ static void div_var_fast(NumericVar* var1, NumericVar* var2, NumericVar* result,
}
Assert(carry == 0);
pfree_ext(div);
if (div != tdiv) {
pfree_ext(div);
}
/*
* Finally, round the result to the requested precision.
@ -5850,12 +5882,8 @@ static void sqrt_var(NumericVar* arg, NumericVar* result, int rscale)
(errcode(ERRCODE_INVALID_ARGUMENT_FOR_POWER_FUNCTION),
errmsg("cannot take square root of a negative number")));
init_var(&tmp_arg);
init_var(&tmp_val);
init_var(&last_val);
/* Copy arg in case it is the same var as result */
set_var_from_var(arg, &tmp_arg);
init_var_from_var(arg, &tmp_arg);
/*
* Initialize the result to the first guess
@ -5867,7 +5895,8 @@ static void sqrt_var(NumericVar* arg, NumericVar* result, int rscale)
result->weight = tmp_arg.weight / 2;
result->sign = NUMERIC_POS;
set_var_from_var(result, &last_val);
init_var_from_var(result, &last_val);
quick_init_var(&tmp_val);
for (;;) {
div_var_fast(&tmp_arg, result, &tmp_val, local_rscale, true);