Taking lot of time to read from SQL Server using c# -


i have 4 million rows in table.( size around 300 gb ), want read rows in table sql server database. used following code in c#. taking time. please suggest me improvements.

            list<int> hit_block_index = new list<int>();              /* here process other , populate hit_block_index integers */              string _query = "select tracename,blockvector trace";              sqlconnection _connection = new sqlconnection(connection_string);              _connection.open();              sqlcommand _command = new sqlcommand(_query, _connection);              sqldatareader data_reader = _command.executereader();              byte[] block_vector=null;              string trace_name = null;              bitarray trace = null;              int max_coverage = 0;              while (data_reader.read())             {                   int coverage = 0;                    block_vector = (byte[])data_reader["blockvector"];                    trace_name = (string)data_reader["tracename"];                    bitarray trace = new bitarray(block_vector);                    foreach (int x in hit_blocks_index)                   {                        if (trace[x])                        {                            coverage++;                        }                   }                    console.writeline("hit count is:" + coverage);                    if (coverage > max_coverage)                   {                          most_covered_trace = trace_name;                          most_covered_array = trace;                          max_coverage = coverage;                   }            }

something might work. i'm not sure on efficiency yet - may depend on amount of hits you're looking for:

create type hitblocks table (     hitindex int not null ) go create procedure findmaxcover     @hits hitblocks readonly     ;with decomposedblocks (         select (hitindex/8)+1 byteindex,power(2,(hitindex%8)) bitmask         @hits     ), coverage (         select             t.tracename,sum(case when substring(t.blockvector,db.byteindex,1) & bitmask != 0 1 else 0 end) coverage                     trace t                 cross join             decomposedblocks db         group             t.tracename     ), ranked (         select *,rank() on (order coverage desc) rk         coverage     )     select         t.tracename,         t.blockvector,         r.coverage             ranked r             inner join         trace t             on                 r.tracename = t.tracename     rk = 1

at moment, return multiple rows if there multiple results same coverage level. may have adjust a) off-by-one errors between expectations , yours, , b) there may endianness issues in computing correct bitmask values.

from code, populate datatable values you're storing in hit_block_index , pass across @hits parameter.


Comments

Post a Comment

Popular posts from this blog

basic authentication with http post params android -

i doing basic authentication passing username , password , using basicnamevaluepair sending post params response service. my method: public stringbuilder callservicehttppost(string username, string password, string type) { // create new httpclient , post header httpclient httpclient = new defaulthttpclient(); httppost httppost = new httppost(webservice + type); httpresponse response = null; stringbuilder total = new stringbuilder(); try { url url = new url(webservice + type); /*string base64encodedcredentials = base64.encodetostring((username + ":" + password).getbytes(), base64.url_safe | base64.no_wrap);*/ string base64encodedcredentials = "basic " + base64.encodetostring( (username + ":" + password).getbytes(), base64.no_wrap); httppost.setheader("auth...
Read more

vb.net - Virtual Keyboard commands -

i wondering difference between virtual these keyboard commands is: keyeventf_extendedkey , keyeventf_keyup is. everywhere have looked gives me description based off integers , not want know each of them does. you've tagged question vb.net, these have nothing @ vb.net. they're constants defined in windows header files, use win32 api functions. as far difference, can't tell looking @ values. individual values not particularly important, that's why named identifiers used. what's important used , documentation functions tells mean. the first one, keyeventf_extendedkey , used keybdinput structure (which used along e.g. sendinput function) pass information synthesized keyboard input. if flag used, means scan code should interpreted extended key. technically, means scan code preceded prefix byte value 224 (&he0 in hexadecimal notation). the second one, keyeventf_keyup , 1 of flags available use structure. means key being released (going up)...
Read more

How to get multiresult with multicondition in Sql Server -

i need solve this. hopefully can giving me advices. for sample, i've got data : proclib.march 1 first 10 rows flight date depart orig dest miles boarded capacity ----------------------------------------------------------------- 114 01mar94 7:10 lga lax 2475 172 210 202 01mar94 10:43 lga ord 740 151 210 219 01mar94 9:31 lga lon 3442 198 250 622 01mar94 12:19 lga fra 3857 207 250 132 01mar94 15:35 lga yyz 366 115 178 271 01mar94 13:17 lga par 3635 138 250 302 01mar94 20:22 lga 229 105 180 114 02mar94 7:10 lga lax 2475 119 210 202 02mar94 10:43 lga ord 740 120 210 219 02mar94 9:31 lga lon 344...
Read more