OTL 4.0, Example 379 (Insert/Update/Select, Oracle 8i/9i/10g CLOBs in stream mode, and std:strings)

This example demonstrates INSERT, UPDATE, and SELECT statements with the Oracle 8i/9i/10g CLOB datatype in stream mode and std::strings.

Source Code

#include <iostream>
#include <string>
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/OCI10g Release2
#define OTL_STL // enable OTL support for STL

#if (defined(__clang__) || defined(__GNUC__)) && \
(defined(OTL_CPP_14_ON) || defined(OTL_CPP_17_ON))
#include <experimental/string_view>
#define OTL_STD_STRING_VIEW_CLASS std::experimental::string_view
#elif defined(_MSC_VER) && (_MSC_VER>=1910) && defined(OTL_CPP_17_ON)
// VC++ 2017 or higher when /std=c++latest is used
#include <string_view>
#define OTL_STD_STRING_VIEW_CLASS std::string_view
#endif

#include <otlv4.h> // include the OTL 4.0 header file

otl_connect db; // connect object

void insert()
// insert rows into table
{
string f2;
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){
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 CLOB to be written.
// It is required for backward compatibility

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

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

db.commit(); // committing transaction.
}
void update()
// insert rows in table
{
 string f2;
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".


f2.append(6000,'#');
f2+='?';

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

lob.set_len(6001*4); // setting the total size of of the CLOB to be written
for(int i=1;i<=4;++i){

#if defined(OTL_STD_STRING_VIEW_CLASS)
OTL_STD_STRING_VIEW_CLASS f2_sv(f2.c_str(),f2.length());
lob<<f2_sv; // writing chunks of the CLOB into the otl_lob_stream
#else
lob<<f2; // writing chunks of the CLOB into the otl_lob_stream
#endif

}
lob.close(); // closing the otl_lob_stream

db.commit(); // committing transaction

}

void select()
{
string f2;

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

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

lob.setStringBuffer(40000); // Set a bigger internal buffer (default is 4096 bytes)
// for reading chunks of the CLOB, before each chunk
// gets appended to the output string.
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;
i>>lob; // initializing CLOB stream by reading the CLOB 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 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, 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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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.