preallocation can be used only when we know number of rows, and for this
we need:
- source clickhouse
- no filtering (i.e. lack of <where>), since filtering can filter
too much rows and eventually it may allocate memory that will
never be used.
For sparse_hash the difference is quite significant, preallocated
sparse_hash hashtable allocates ~33% faster (7.5 seconds vs 5 seconds
for insert, and the difference is more significant for higher number of
elements):
$ ninja bench-sparse_hash-run
[1/1] cd /src/ch/hashtable-bench/.cmake && ...ch/hashtable-bench/.cmake/bench-sparse_hash
sparse_hash/insert: 7.574 <!--
sparse_hash/find : 2.14426
sparse_hash/maxrss: 174MiB
sparse_hash/time: 9710.51 msec (user+sys)
$ time ninja bench-sparse_hash-preallocate-run
[1/1] cd /src/ch/hashtable-bench/.cmake && ...-bench/.cmake/bench-sparse_hash-preallocate
sparse_hash/insert: 5.0522 <!--
sparse_hash/find : 2.14024
sparse_hash/maxrss: 174MiB
sparse_hash/time: 7192.06 msec (user+sys)
P.S. the difference for sparse_hashed dictionary with 4e9 elements
(uint64, uint16) is ~18% (4975.905 vs 4103.569 sec)
v2: do not reallocate the dictionary from the progress callback
Since this will access hashtable in parallel.
v3: drop PREALLOCATE() and do this only for source=clickhouse and empty
<where>
* Docs for the extractAllGroupsHorizontal and extractAllGroupsVertical functions (English).
* Minor fixes (en).
* Misspelling fixed.
* English docs corrected and translated into Russian.
* English misspelling corrected.
Co-authored-by: Olga Revyakina <revolg@yandex.ru>
Co-authored-by: Olga Revyakina <revolg@yandex-team.ru>
* Higher-order functions description moved to Array functions (English).
* Bad anchor fixed.
* Update docs/en/sql-reference/functions/array-functions.md
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
* Higher-order functions description moved to Array functions (Russian).
* Update array-functions.md
Minor fixes in Russian text.
Co-authored-by: Olga Revyakina <revolg@yandex.ru>
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
* Updated docs in English and docs in Russian.
* Updated docs in English and docs in Russian.
* Docs in Russian.
Co-authored-by: Olga Revyakina <revolg@yandex-team.ru>
* En docs for groupArraySample function.
* Bug fixed.
* Update docs/en/sql-reference/aggregate-functions/reference/grouparraysample.md
Co-authored-by: Olga Revyakina <revolg@yandex-team.ru>
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
* Docs in English for optimize_read_in_order setting.
* Link misspelling fixed.
* Usage section moved to the ORDER BY topic.
* Link fixed.
* Update docs/en/sql-reference/statements/select/order-by.md
Co-authored-by: BayoNet <da-daos@yandex.ru>
* Update docs/en/sql-reference/statements/select/order-by.md
Co-authored-by: BayoNet <da-daos@yandex.ru>
* Apply suggestions from code review
Co-authored-by: BayoNet <da-daos@yandex.ru>
* Apply suggestions from code review
Co-authored-by: BayoNet <da-daos@yandex.ru>
* Update docs/en/sql-reference/statements/select/order-by.md
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
* Small fix in English and translation into Russian.
Co-authored-by: Olga Revyakina <revolg@yandex-team.ru>
Co-authored-by: BayoNet <da-daos@yandex.ru>
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
* CLICKHOUSEDOCS-733: Fixed some broken links. Updated introduction and TOC in aggregate functions.
* CLICKHOUSEDOCS-733: Fixed files endings.
* CLICKHOUSEDOCS-733: Returned the list of functions back to reference index.
Co-authored-by: Sergei Shtykov <bayonet@yandex-team.ru>
Co-authored-by: emironyuk <em@don.ru>
* Docs in English.
* Fixed links bug.
* Update docs/en/sql-reference/statements/alter/delete.md
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
* Translated into Russian. Anchors in links syncronized with English text. One minor change in English text to unify two similar descriptions.
Co-authored-by: Olga Revyakina <revolg@yandex-team.ru>
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
* Geo functions - en/ru sync.
* Fixed bug with levels.
* Apply suggestions from code review
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
Co-authored-by: BayoNet <da-daos@yandex.ru>
* Geo functions splitted into 3 files.
* Links fixed.
* Link fixed.
* Anchor fixed.
* Add into TOC.
* Temporarily removed anchors.
* Working on TOC.
* Links to original article.
* TOC and links in English and Russian.
* TOC in English, content in index.
* Link fixed.
* TOC in Russian, with content in index file.
* Added index file to geo functions
* fixed links in ru
Co-authored-by: Olga Revyakina <revolg@yandex-team.ru>
Co-authored-by: Ivan Blinkov <github@blinkov.ru>
Co-authored-by: BayoNet <da-daos@yandex.ru>
Co-authored-by: Sergei Shtykov <bayonet@yandex-team.ru>
