ext/pgsql: adding pg_result_memory_size. #14214
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| @@ -66,6 +66,7 @@ if test "$PHP_PGSQL" != "no"; then | |||
| AC_CHECK_LIB(pq, pg_encoding_to_char,AC_DEFINE(HAVE_PGSQL_WITH_MULTIBYTE_SUPPORT,1,[Whether libpq is compiled with --enable-multibyte])) | |||
| AC_CHECK_LIB(pq, lo_truncate64, AC_DEFINE(HAVE_PG_LO64,1,[PostgreSQL 9.3 or later])) | |||
| AC_CHECK_LIB(pq, PQsetErrorContextVisibility, AC_DEFINE(HAVE_PG_CONTEXT_VISIBILITY,1,[PostgreSQL 9.6 or later])) | |||
| AC_CHECK_LIB(pq, PQresultMemorySize, AC_DEFINE(HAVE_PG_RESULT_MEMORY_SIZE,1,[PostgreSQL 12 or later])) | |||
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NOTE:
PostgreSQL: Documentation: 12: E.20. Release 12
https://www.postgresql.org/docs/12/release-12.html#id-1.11.6.24.5.9
E.20.3.7. Client Interfaces
- Add libpq function
PQresultMemorySize()to report the memory used by a query result (Lars Kanis, Tom Lane)
No, it s not necessary in this case neither. |
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Looks pretty straightforward and correct, will look again later today. |
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| $db = pg_connect($conn_str); | ||
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| $result = pg_query($db, 'select 1'); |
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question: is the memory usage deterministic right ? If that s the case if I redo this query it should be the same amount correct ?
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The memory usage returned by PQresultMemorySize() for the same query is generally consistent, but this cannot be guaranteed in all cases due to several factors:
- Version of libpq: Although significant differences are unlikely, the lack of documented specifications of
libpqmeans we cannot ensure identical behavior across all versions. - CPU architecture: Differences in architecture could potentially influence memory usage.
- Query purity: Non-deterministic elements, such as the output of
VOLATILEfunctions or results fromINSERT INTO .. RETURNING .../UPDATE ... RETURNING, can affect the memory used.
Based on some tests with simple queries, the memory usage has been consistent when none of these variables are at play. However, I must note that I am not deeply familiar with the internal implementation of libpq, so while my response is based on research and tests, it might not cover all possible scenarios.
(For the above reasons, I did not write the output size directly in the test, but instead tested by comparing the two results)
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Thanks for the detail but what I meant if within your test if I do
$result = pg_query($db, 'select 1');
$size_3 = pg_result_memory_size($result);
var_dump($size_1 == $size_3);it should be true then ?
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Yes, true in that case.
(Although not guaranteed, I don't think this behavior will change.)
Retrieve the memory usage of the query result resource.
Returns the value of
PQresultMemorySize()provided by the client librarylibpqas is. The memory here is allocated internally bylibpq, so until now there was no way for the user to directly check it.Is an RFC necessary to introduce this feature? Although
pg_set_error_context_visibility()added in #11395 did not require an RFC, please confirm if one is needed for this case.