OTL 4.0, Example 385 (Insert/Update/Select with Oracle 8i/9i/10g CLOB in stream mode and otl_long_string::set_last_piece())

This example demonstrates INSERT, UPDATE, and SELECT statements with the Oracle 8 CLOB datatype in stream mode and otl_long_string::set_last_piece().

Source Code

#include <iostream>
using namespace std;

#include <stdio.h>
#define OTL_ORA8I // Compile OTL 4.0/OCI8i
//#define OTL_ORA9I // Compile OTL 4.0/OCI9i
//#define OTL_ORA10G // Compile OTL 4.0/OCI10g
//#define OTL_ORA10G_R2 // Compile OTL 4.0/OCI10gR2
#include <otlv4.h> // include the OTL 4.0 header file

otl_connect db; // connect object

void insert()
// insert rows into table
{otl_long_string f2(60000); // define long string variable
otl_stream o(1, // buffer size has to be set to 1 for operations with LOBs
"insert into test_tab values(:f1<int>,empty_clob()) "
"returning f2 into :f2<clob> ",
// SQL statement
db // connect object
);
o.set_commit(0); // setting stream "auto-commit" to "off". It is required
// when LOB stream mode is used.

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){
for(int j=0;j<50000;++j)
f2[j]='*';
f2[50000]='?';
f2.set_len(50001);

o<<i;

o<<lob; // Initialize otl_lob_stream by writing it
// into otl_stream. Weird, isn't it?

// OTL 4.0.138 and higher does not require the LOB's total length to be
// set beforehand. Instead, otl_long_string::last_piece can be used.
// lob.set_len(50001+23123); // setting the total size of
// // the CLOB to be written.
// // It is required for compatibility
// // with earlier releases of OCI8: OCI8.0.3, OCI8.0.4.

f2.set_last_piece(false);
lob<<f2; // writing first chunk of the CLOB into lob

f2[23122]='?';
f2.set_len(23123); // setting the size of the second chunk

f2.set_last_piece(true);
lob<<f2; // writing the second (last) chunk of the CLOB into lob
lob.close(); // closing the otl_lob_stream
}

db.commit(); // committing transaction.
}
void update()
// insert rows in table
{
 otl_long_string f2(6200); // define long string variable

otl_stream o(1, // buffer size has to be set to 1 for operations with LOBs
"update test_tab "
" set f2=empty_clob() "
"where f1=:f1<int> "
"returning f2 into :f2<clob> ",
// SQL statement
db // connect object
);

otl_lob_stream lob;

o.set_commit(0); // setting stream "auto-commit" to "off".


for(int j=0;j<6000;++j){
f2[j]='#';
}

f2[6000]='?';
f2.set_len(6001);

o<<5;
o<<lob; // Initialize otl_lob_stream by writing it
// into otl_stream.

// OTL 4.0.138 and higher does not require the LOB's total length to be
// set beforehand. Instead, otl_long_string::last_piece can be used.
// lob.set_len(6001*4); // setting the total size of of the CLOB to be written

for(int i=1;i<=4;++i){
f2.set_last_piece(i==4);
lob<<f2; // writing chunks of the CLOB into the otl_lob_stream
}

lob.close(); // closing the otl_lob_stream

db.commit(); // committing transaction

}

void select()
{
otl_long_string f2(20000); // define long string variable

otl_stream i(10, // buffer size. To read CLOBs, it can be set to a size greater than 1
"select * from test_tab where f1>=:f<int> and f1<=:f*2",
// SELECT statement
db // connect object
);
// create select stream

float f1;
otl_lob_stream lob; // Stream for reading CLOB

i<<4; // assigning :f = 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<<endl;
i>>lob; // initializing CLOB stream by reading the CLOB reference
// into the otl_lob_stream from the otl_stream.
int n=0;
while(!lob.eof()){ // read while not "end-of-file" -- end of CLOB
++n;
lob>>f2; // reading a chunk of CLOB
cout<<" chunk #"<<n;
cout<<", f2="<<f2[0]<<f2[f2.len()-1]<<", len="<<f2.len()<<endl;
}
lob.close(); // closing the otl_lob_stream. This step may be skipped.

}

}

int main()
{
otl_connect::otl_initialize(); // initialize OCI environment
try{

db.rlogon("scott/tiger"); // connect to Oracle

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 number, f2 clob)"
); // 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 Oracle

return 0;

}

Output

f1=4
chunk #1, f2=**, len=20000
chunk #2, f2=**, len=20000
chunk #3, f2=**, len=20000
chunk #4, f2=*?, len=13124
f1=5
chunk #1, f2=##, len=20000
chunk #2, f2=#?, len=4004
f1=6
chunk #1, f2=**, len=20000
chunk #2, f2=**, len=20000
chunk #3, f2=**, len=20000
chunk #4, f2=*?, len=13124
f1=7
chunk #1, f2=**, len=20000
chunk #2, f2=**, len=20000
chunk #3, f2=**, len=20000
chunk #4, f2=*?, len=13124
f1=8
chunk #1, f2=**, len=20000
chunk #2, f2=**, len=20000
chunk #3, f2=**, len=20000
chunk #4, f2=*?, len=13124


Examples Contents Go Home

Copyright © 1996-2017, Sergei Kuchin, email: skuchin@gmail.com, skuchin@gmail.com .

Permission to use, copy, modify and redistribute this document for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.