This example demonstrates INSERT, UPDATE, and SELECT statements with
the Oracle 8 CLOB datatype in stream mode
and otl_long_string::set_last_piece().
#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;
}
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
Copyright © 1996-2024, Sergei Kuchin, email: skuchin@gmail.com, skuchin@gmail.com .
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