OTL 4.0, Example 382 (Insert/Update/Select, MySQL LONGTEXT in stream mode, and std:strings)

This example demonstrates INSERT, UPDATE, and SELECT statements with the MySQL LONGTEXT datatype in stream mode and std::strings.

Source Code

#include <iostream>
#include <string>
using namespace std;

#include <stdio.h>
#define OTL_ODBC // Compile OTL 4.0/ODBC
#define OTL_STL // enable OTL support for STL
#include <otlv4.h> // include the OTL 4.0 header file

otl_connect db; // connect object

void insert()
// insert rows into table
{
string f2;
 otl_nocommit_stream o; // defined an otl_stream variable
 o.set_lob_stream_mode(true); // set the "lob stream mode" flag
 o.open(1, // buffer size has to be set to 1 for operations with LOBs
        "insert into test_tab values(:f1<int>,:f2<varchar_long>) ",
            // SQL statement
        db // connect object
       );
otl_lob_stream lob; // LOB stream for reading/writing unlimited number
// of bytes regardless of the buffer size.
for(int i=1;i<=20;++i){
f2.erase();
f2.append(50000,'*');
f2 += '?';
o<<i;
o<<lob; // Initialize otl_lob_stream by writing it
// into otl_stream

lob.set_len(50001+23123); // setting the total size of
// the LONGTEXT to be written.
// It is required for bakward compatibility

lob<<f2; // writing first chunk of the LONGTEXT into lob

f2.erase();
f2.append(23122,'*');
f2 += '?';
lob<<f2; // writing the second chunk of the LONGTEXT into lob
lob.close(); // closing the otl_lob_stream
}

db.commit(); // committing transaction.
}
void update()
// insert rows in table
{
string f2;
 otl_stream o; // defined an otl_stream variable
 o.set_lob_stream_mode(true); // set the "lob stream mode" flag
 o.open(1, // buffer size has to be set to 1 for operations with LOBs
"update test_tab "
" set f2=:f2<varchar_long> "
"where f1=:f1<int> ",
            // SQL statement
        db // connect object
       );
otl_lob_stream lob;
o.set_commit(0); // setting stream "auto-commit" to "off".
f2.append(6000,'#');
f2+='?';
o<<lob; // Initialize otl_lob_stream by writing it
// into otl_stream.
o<<5;
lob.set_len(6001*4); // setting the total size of of the LONGTEXT to be written
for(int i=1;i<=4;++i)
lob<<f2; // writing chunks of the LONGTEXT into the otl_lob_stream
lob.close(); // closing the otl_lob_stream
db.commit(); // committing transaction

}

void select()
{
string f2;
 otl_stream i; // defined an otl_stream variable
 i.set_lob_stream_mode(true); // set the "lob stream mode" flag
 i.open(1, // buffer size. To read LONGTEXTs, it should be set to 1
        "select * from test_tab where f1>=:f11<int> and f1<=:f12<int>*2",
         // SELECT statement
        db // connect object
       ); 
   // create select stream

int f1;
otl_lob_stream lob; // Stream for reading LONGTEXT

lob.setStringBuffer(40000); // Set a bigger internal buffer (default is 4096 bytes)
// for reading chunks of the LONGTEXT, before each chunk
// gets appended to the output string.
i<<4<<4; // assigning :f11 = 4, :f12 = 4
// SELECT automatically executes when all input variables are
// assigned. First portion of output rows is fetched to the buffer

while(!i.eof()){ // while not end-of-data
i>>f1;
cout<<"f1="<<f1;
i>>lob; // initializing LONGTEXT stream by reading the LONGTEXT reference
// into the otl_lob_stream from the otl_stream.
lob>>f2;
cout<<", f2="<<f2[0]<<f2[f2.length()-1]<<", len="<<(int)f2.length()<<endl;
lob.close(); // closing the otl_lob_stream. This step may be skipped.

}

}

int main()
{
otl_connect::otl_initialize(); // initialize the database API environment
try{

db.rlogon("scott/tiger@mysql35"); // connect to the database

otl_cursor::direct_exec
(
db,
"drop table test_tab",
otl_exception::disabled // disable OTL exceptions
); // drop table

otl_cursor::direct_exec
(
db,
"create table test_tab(f1 int, f2 longtext) type=innoDB"
); // create table

insert(); // insert records into table
update(); // update records in table
select(); // select records from table

}

catch(otl_exception& p){ // intercept OTL exceptions
cerr<<p.msg<<endl; // print out error message
cerr<<p.stm_text<<endl; // print out SQL that caused the error
cerr<<p.var_info<<endl; // print out the variable that caused the error
}

db.logoff(); // disconnect from the database

return 0;

}

Output

f1=4, f2=*?, len=73124
f1=5, f2=#?, len=24004
f1=6, f2=*?, len=73124
f1=7, f2=*?, len=73124
f1=8, f2=*?, len=73124


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