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INTERNAL: Remove dummy fetch in the get API #334

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Feb 20, 2025
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INTERNAL: Remove dummy fetch in the get API #334

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53 changes: 29 additions & 24 deletions libmemcached/get.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -485,6 +485,12 @@ char *memcached_get_by_key(memcached_st *ptr,
{
arcus_server_check_for_update(ptr);

if (value_length)
*value_length= 0;

if (flags)
*flags= 0;

memcached_return_t unused;
if (error == NULL)
error= &unused;
Expand All @@ -503,11 +509,6 @@ char *memcached_get_by_key(memcached_st *ptr,
*error= memcached_last_error(ptr);
}

if (value_length)
{
*value_length= 0;
}

return NULL;
}

Expand Down Expand Up @@ -540,20 +541,36 @@ char *memcached_get_by_key(memcached_st *ptr,
*error= memcached_last_error(ptr);
}

if (value_length)
*value_length= 0;

return NULL;
}

char *value= memcached_fetch(ptr, NULL, NULL,
value_length, flags, error);
char *value= NULL;
bool is_value_fetched= false;
memcached_result_st *result= &ptr->result;

while (memcached_fetch_result(ptr, result, error) != NULL)
{
is_value_fetched= true;
if (value != NULL)
libmemcached_free(ptr, value);
value= memcached_string_take_value(&result->value);
if (value_length)
*value_length= memcached_string_length(&result->value);
if (flags)
*flags= result->item_flags;
}
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memcached_fetch_result() != NULL ๊ฒฝ์šฐ๊ฐ€ 2ํšŒ ์ด์ƒ ๋ฐœ์ƒํ•˜๋Š” ๊ฒฝ์šฐ๋„ ๊ณ ๋ คํ•˜์‹œ์ฃ .

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memcached_fetch_result() != NULL ๊ฒฝ์šฐ๊ฐ€ 2ํšŒ ์ด์ƒ ๋ฐœ์ƒํ•˜๋Š” ๊ฒฝ์šฐ๋„ ๊ณ ๋ คํ•˜์‹œ์ฃ .

์˜ˆ์ „์— ์ด๋ ‡๊ฒŒ ์ฝ”๋ฉ˜ํŠธ ํ–ˆ์ง€๋งŒ, ์ด๋Ÿฌํ•œ ๊ฒฝ์šฐ๊ฐ€ ๋ฐœ์ƒํ•˜์ง€ ์•Š๋Š”๋‹ค๊ณ  ๋ณด๋Š” ๊ฒƒ์ด ๋งž๊ฒ ์ฃ ?
๋งŒ์•ฝ์˜ SW ๋ฒ„๊ทธ๋ฅผ ๊ณ ๋ คํ•˜๋”๋ผ๋„ END ์ด์ „์˜ ๊ฐ€์žฅ ๋งˆ์ง€๋ง‰ ๊ฐ’์„ ๋ฐ˜ํ™˜ํ•˜๋ฉด ๋  ๊ฒƒ ๊ฐ™์Šต๋‹ˆ๋‹ค.

  *error = ENGINE_SUCCESS;
  while (memcached_fetch_result(ptr, result, error) != NULL)
  {
    value= memcached_string_take_value(&result->value);
    if (value_length)
      *value_length= memcached_string_length(&result->value);
    if (flags)
      *flags= result->item_flags;
  }

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while loop ์•ˆ์— ์•„๋ž˜ ์ฝ”๋“œ๊ฐ€ ์žˆ์–ด์•ผ ํ•˜์ฃ ?

if (value) 
  memcached_free(value);


assert_msg(ptr->query_id >= query_id +1, "Programmer error, the query_id was not incremented.");
//assert_msg(ptr->query_id == query_id +1, "Programmer error, the query_id was not incremented.");

/* This is for historical reasons */
if (*error == MEMCACHED_END)
if (is_value_fetched)
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is_value_fetched ๋ผ๋Š” ๋ณ€์ˆ˜๊ฐ€ ํ•„์š”ํ•œ๊ฐ€์š”?

์•„๋ž˜์™€ ๊ฐ™์ด ๊ฒ€์‚ฌํ•˜๋ฉด ๋˜์ง€ ์•Š๋‚˜์š”?

if (value)

{
*error= MEMCACHED_SUCCESS;
}
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success_occurred ๊ฒฝ์šฐ๋Š” value != NULL ์ƒํƒœ์ž…๋‹ˆ๋‹ค.
success_occurred ๋ณ€์ˆ˜๊ฐ€ ํ•„์š” ์—†์„ ๊ฒƒ ๊ฐ™์Šต๋‹ˆ๋‹ค.

๊ทธ๋ฆฌ๊ณ , ์ด๋Ÿฌํ•œ ์ฝ”๋“œ๋Š” value == NULL ๊ฒฝ์šฐ์— ๋Œ€ํ•œ ์ฒ˜๋ฆฌ ์ฝ”๋“œ ๋‹ค์Œ์— ์œ„์น˜ํ•˜๋Š” ๊ฒƒ์ด ์ข‹๊ฒ ์Šต๋‹ˆ๋‹ค.

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@ing-eoking ing-eoking Jan 17, 2025 •
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value์— ๋นˆ ๋ฌธ์ž์—ด์„ ์ €์žฅํ–ˆ์„ ๊ฒฝ์šฐ, value == NULL์ด ๋  ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค.

์šฉ์–ด๋ฅผ success_occurred์—์„œ is_value_fetched๋กœ ๋ณ€๊ฒฝํ–ˆ์Šต๋‹ˆ๋‹ค.

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@ing-eoking
์งˆ๋ฌธ์ž…๋‹ˆ๋‹ค.

  • value == ""(๋นˆ ๋ฌธ์ž์—ด)์„ ์ €์žฅํ•˜๊ณ  ๋‚˜์„œ, ์ด๋ฅผ ์กฐํšŒํ•˜๋ฉด ๋นˆ ๋ฌธ์ž์—ด์ด ๋ฆฌํ„ด๋˜์–ด์•ผ ํ•˜์ง€ ์•Š๋‚˜์š”?
  • value == NULL๋กœ ํ•ด์„œ ์ €์žฅํ•  ์ˆ˜ ์žˆ๋‚˜์š”?

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result->value์—๋Š” ๋นˆ ๋ฌธ์ž์—ด์ด ๋“ค์–ด๊ฐ€๋Š”๋ฐ, ์ด๋ฅผ ๋‹ค์‹œ value์— copyํ•˜์—ฌ ๋„ฃ๋Š” ๊ณผ์ •์—์„œ NULL๋กœ ๋ณ€ํ™˜๋ฉ๋‹ˆ๋‹ค.
memcached_string_take_value ํ•จ์ˆ˜ ๋‚ด๋ถ€ ๋™์ž‘์—์„œ ๋ฌธ์ž์—ด์˜ ๊ธธ์ด๊ฐ€ 0์ด๋ฉด NULL์„ ๋ฐ˜ํ™˜ํ•˜๋„๋ก ๋˜์–ด ์žˆ๊ธฐ ๋•Œ๋ฌธ์ž…๋‹ˆ๋‹ค

if (not memcached_string_length(string))
    return NULL;

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value == NULL๋กœ ํ•ด์„œ ์ €์žฅํ•  ์ˆ˜ ์žˆ๋‚˜์š”?

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@ing-eoking ing-eoking Feb 19, 2025 •
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value == NULL๋กœ ํ•ด์„œ ์ €์žฅํ•  ์ˆ˜ ์žˆ๋‚˜์š”?

๋ถˆ๊ฐ€๋Šฅํ•ฉ๋‹ˆ๋‹ค. ์„œ๋ฒ„ ์ธก์—์„œ๋Š” value์— NULL ๊ฐ’์„ ์ €์žฅํ•  ์ˆ˜ ์—†์œผ๋ฉฐ,
ํด๋ผ์ด์–ธํŠธ ์ธก์—๋„ NULL Value๋ฅผ ์ฒ˜๋ฆฌํ•˜๋Š” ๊ธฐ๋Šฅ์ด ์—†์Šต๋‹ˆ๋‹ค.

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value = NULL, value_length = 0์œผ๋กœ ํ•˜์—ฌ set ํ•˜๋ฉด ์–ด๋–ค ์˜ค๋ฅ˜๊ฐ€ ๋ฐœ์ƒํ•˜๋‚˜์š”?

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value_length๊ฐ€ 0์ด๋ฏ€๋กœ ๋นˆ๋ฌธ์ž์—ด์ด ๋“ค์–ด๊ฐ€๊ฒŒ ๋ฉ๋‹ˆ๋‹ค.

memcached_set(memc, "i", 1, NULL, 0, 0, 0);
/* telnet */
get i
VALUE i 0 0

END

else if (*error == MEMCACHED_END)
{
*error= MEMCACHED_NOTFOUND;
}

if (value == NULL)
{
Expand Down Expand Up @@ -607,18 +624,6 @@ char *memcached_get_by_key(memcached_st *ptr,
return NULL;
}

size_t dummy_length;
uint32_t dummy_flags;
memcached_return_t dummy_error;

char *dummy_value= memcached_fetch(ptr, NULL, NULL,
&dummy_length, &dummy_flags,
&dummy_error);
assert_msg(dummy_value == 0, "memcached_fetch() returned additional values beyond the single get it expected");
assert_msg(dummy_length == 0, "memcached_fetch() returned additional values beyond the single get it expected");
assert_msg(ptr->query_id >= query_id +1, "Programmer error, the query_id was not incremented.");
//assert_msg(ptr->query_id == query_id +1, "Programmer error, the query_id was not incremented.");

return value;
}

Expand Down
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