Details
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Task
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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None
Description
Recent benchmarks made by axel revealed that CPU is unnecessarily wasted on character string conversion for numeric data types, e.g. in this scenario:
SET NAMES utf8; |
CREATE OR REPLACE TABLE t1 (a INT); |
INSERT INTO t1 VALUES (1); |
SELECT a FROM t1; |
Although no character set conversion is needed in this case, the execution gets int my_convert() with this stack:
#0 my_convert (to=0x7fff8c00dfa9 "def\004test\002t1\002t1\001a\001a\f?",
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to_length=3, to_cs=0x55555789b500 <my_charset_utf8mb3_general_ci>,
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from=0x7ffff4bebbc0 "1q\315VUU", from_length=1,
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from_cs=0x5555577952c0 <my_charset_latin1>, errors=0x7ffff4bebae4)
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at /home/bar/maria-git/server.10.5.clu/strings/ctype.c:1225
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#1 0x0000555555d40f3b in copy_and_convert (
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to=0x7fff8c00dfa9 "def\004test\002t1\002t1\001a\001a\f?", to_length=3,
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to_cs=0x55555789b500 <my_charset_utf8mb3_general_ci>,
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from=0x7ffff4bebbc0 "1q\315VUU", from_length=1,
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from_cs=0x5555577952c0 <my_charset_latin1>, errors=0x7ffff4bebae4)
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at /home/bar/maria-git/server.10.5.clu/sql/sql_string.h:51
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#2 0x0000555555d3bca3 in Protocol::net_store_data_cs (this=0x7fff8c001340,
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from=0x7ffff4bebbc0 "1q\315VUU", length=1,
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from_cs=0x5555577952c0 <my_charset_latin1>,
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to_cs=0x55555789b500 <my_charset_utf8mb3_general_ci>)
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at /home/bar/maria-git/server.10.5.clu/sql/protocol.cc:118
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#3 0x0000555555d3ec51 in Protocol::store_string_aux (this=0x7fff8c001340,
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from=0x7ffff4bebbc0 "1q\315VUU", length=1,
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fromcs=0x5555577952c0 <my_charset_latin1>,
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tocs=0x55555789b500 <my_charset_utf8mb3_general_ci>)
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at /home/bar/maria-git/server.10.5.clu/sql/protocol.cc:1186
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#4 0x0000555555d3fa62 in Protocol_text::store (this=0x7fff8c001340,
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field=0x7fff8c086158)
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at /home/bar/maria-git/server.10.5.clu/sql/protocol.cc:1340
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#5 0x00005555561f790f in Item_field::send (this=0x7fff8c016a20,
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protocol=0x7fff8c001340, buffer=0x7ffff4bebf90)
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at /home/bar/maria-git/server.10.5.clu/sql/item.cc:7229
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#6 0x0000555555d3e823 in Protocol::send_result_set_row (this=0x7fff8c001340,
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row_items=0x7fff8c014ff8)
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Let's fix the code to avoid this conversion:
- Add a new parameter of the my_repertoire_t to Protocol::store_string_aux()
- Fix Protocol_text::store() and all affected functions to pass the Field's repertoire inside store_string_aux()
- Fix Protocol::store_string_aux() to use memcpy() instead of my_convert() if the source repertoire is MY_REPERTOIRE_ASCII and character_set_results is ASCII-compatible.
This should improve performance slightly.
Attachments
Issue Links
- is blocked by
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MDEV-23282 FLOAT(53,0) badly handles out-of-range values
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- Closed
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- relates to
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- Closed
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- Closed
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