Hi all,
I create a table with 200 columns, then use sqlite3_prepare() and
sqlite3_step()to get a record by this: "select * from tbl where ID =.. ".
Test in my
embedded system,The total time is about 65ms,it is too long for the
performance
requirement, I found sqlite3_prepare() time is about 50ms.
Then test the code with VTune,I found lookupName() function in Sqlite
take about 50% of the total time, and sqlite3StrICmp() occupied most
execution time
(867/922, see the follow pics ) in lookupName().
The follow is the graph info link generated by VTune:
http://img15.tianya.cn/photo/2008/11/18/10872206_2807293.jpg
http://img15.tianya.cn/photo/2008/11/18/10872205_2807293.jpg
If use "select * from tbl where...." ,tbl is a table with 200
columns,
sqlite3StrICmp() will be executed more than 20000 times inlookupName(),
this is the main bottleneck in sqlite3_prepare().
I think maybe Sqlite should do a special optimization for "select *
from tbl .......",
and there is no necessary to compare the column names expanded by "*" with
the table
column names.
Are there some efficient ways to get a whole record with many many
columns ?
Thanks very much!
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