Re: [Cppcms-users] Avoid loading query results completely into cppdb::result

[Artyom B. <art...@ya...>]

CppDB (if the backed allows) fetches the data row by row and not the entire collection:
Unprepared statements: http://sourceforge.net/p/cppcms/code/HEAD/tree/cppdb/trunk/drivers/mysql_backend.cpp#l75
Prepared statement: http://sourceforge.net/p/cppcms/code/HEAD/tree/cppdb/trunk/drivers/mysql_backend.cpp#l510
  cppdb::result is sort of cursor you iterate over the data set. 
The delay probably caused by initial query and not fetching itself.
 Artyom Beilis
--------------
CppCMS - C++ Web Framework:   http://cppcms.com/
CppDB - C++ SQL Connectivity: http://cppcms.com/sql/cppdb/
 
      From: Alexander Mack (EvalSys) <a....@ev...>
 To: cpp...@li... 
 Sent: Wednesday, April 1, 2015 12:36 PM
 Subject: [Cppcms-users] Avoid loading query results completely into cppdb::result
   
  Dear Artyom, Dear community,
 
 I was wondering if it's possible, to avoid loading the complete query result into cppdb::result but handle the query results "step by step"?
 
 If I'm running the following query on a bigger database
 
 <code>
 cppdb::result r = sql << "SELECT name,age FROM students";

 </code>
 
 it takes a lot of time to copy all the results into the cppdb::result container. For testing I tried that for about 6 mio entries.. 
 
 I didn't work with the original MySQL-lib yet.. but if I send the query using the standard MySQL lib e.g.
 
 <code>
 
  res = mysql_perform_query(conn, "SELECT * FROM students");

  while ((row = mysql_fetch_row(res)) !=NULL)
      .... </code>
 
 it seems that the interface delivers single rows only, if I'm fetching the result (row by row).
 
 Now I was wondering, if there is some technique / flag to do the same with cppdb? 
 
 In the end I'm trying to run through a big amount of data. If I'm trying offset/limit combinations, it gets very slow as soon as offset increases..
 
 It'd be great, if someone would have a tipp for me.
 
 Thank you very much,
 
 Alex
 
 
 
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