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|_| |_|_(_)_/ \_\ |_| |_| |_| \_/ \__,_|\__\___| |_____/|_| |_|\___V 2.1
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Program update;
{*
* PROGRAM: Object oriented API samples.
* MODULE: 02.update.cpp
* DESCRIPTION: Run once prepared statement with parameters
* a few times, committing transaction after each run.
* Learns how to prepare statement, manually define parameters
* for it, execute that statement with different parameters
* and perform non-default error processing.
*
* Example for the following interfaces:
* IAttachment - database attachment
* ITransaction - transaction
* IStatement - SQL statement execution
* IMessageMetadata - describe input and output data format
* IMetadataBuilder - tool to modify/create metadata
* IStatus - return state holder
*
* Note that all updates are rolled back in this version. (see *** later)
*
* Run something like this to build the program :
*
* fpc -Fu./common -Fu/opt/firebird/include/firebird -FUlib -oupdate 02.update.pas
*
* The contents of this file are subject to the Initial
* Developer's Public License Version 1.0 (the "License");
* you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
* https://www.ibphoenix.com/about/firebird/idpl.
*
* Software distributed under the License is distributed AS IS,
* WITHOUT WARRANTY OF ANY KIND, either express or implied.
* See the License for the specific language governing rights
* and limitations under the License.
*
* The Original Code was created by Paul Reeves
* for the Firebird Open Source RDBMS project.
*
* All Rights Reserved.
* Contributor(s): ______________________________________.
*
*}
{$mode Delphi}{$H+}
Uses
SysUtils,
Firebird;
Type
Buffer = String [255];
Var
// master and status are required for all access to the API.
// This is main interface of firebird, and the only one
// for getting which there is special function in our API
master: IMaster;
// Status is used to return error description to user
status: IStatus;
// Provider is needed to start to work with database (or service)
prov: IProvider;
// declare pointers to required interfaces
att: IAttachment;
tra: ITransaction;
// Interface executes prepared SQL statement
stmt: IStatement;
// Interfaces provides access to format of data in messages
meta: IMessageMetadata;
// Interface makes it possible to change format of data or define it yourself
builder: IMetadataBuilder;
Dept_Data: Array[0..4] Of String = ( '622', '100', '116', '900', '0' );
Percent_data: Array[0..4] Of Double = ( 0.05, 1.00, 0.075, 0.10, 0 );
i: Integer;
InputBuffer: Buffer;
len: Integer;
PPercent_inc: PChar;
PDept_no: PChar;
Const
UpdateString = 'UPDATE department SET budget = ? * budget + budget WHERE dept_no = ?';
SQL_DIALECT_V6 = 3;
SQL_DIALECT_CURRENT = SQL_DIALECT_V6;
SQL_TEXT = 452; // CHAR
SQL_DOUBLE = 480; // DOUBLE PRECISION
Procedure PrintError( AMaster: IMaster; AStatus: IStatus );
Var
maxMessage: Integer;
outMessage: PAnsiChar;
Begin
maxMessage := 256;
outMessage := StrAlloc( maxMessage );
AMaster.getUtilInterface.formatStatus( outMessage, maxMessage, AStatus );
writeln( outMessage );
StrDispose( outMessage );
End;
// Get the department and percent parameters for an example to run.
Begin
master := fb_get_master_interface;
status := master.getStatus;
Try
// the main dispatcher is returned by a call to IMaster
// no errors can occur - this function will always succeed
prov := master.getDispatcher;
// We assume that ISC_USER and ISC_PASSWORD env vars are set. Otherwise,
// see code in 01.create for an example of setting the un/pw via the dpb.
att := prov.attachDatabase( status, 'employee', 0, nil );
writeln( 'Attached to database employee.fdb' );
// start transaction
tra := att.startTransaction( status, 0, nil );
// prepare statement
stmt := att.prepare( status, tra, 0, UpdateString, SQL_DIALECT_CURRENT, 0 );
// build metadata
// IMaster creates empty new metadata in builder
builder := master.getMetadataBuilder( status, 2 );
// set required info on fields
builder.setType( status, 0, SQL_DOUBLE + 1 );
builder.setType( status, 1, SQL_TEXT + 1 );
builder.setLength( status, 1, 3 );
// IMetadata should be ready
meta := builder.getMetadata( status );
// no need for builder any more
builder.Release( );
builder := nil;
len := meta.getMessageLength( status );
If ( len > sizeof( InputBuffer ) ) Then
Raise Exception.Create( 'Input message length too big - cannot continue' )
Else
FillChar( InputBuffer, SizeOf( InputBuffer ), 0 );
i := meta.getNullOffset( status, 0 );
InputBuffer[i] := Char( 0 );
i := meta.getNullOffset( status, 1 );
InputBuffer[i] := Char( 0 );
Try
// locations of parameters in input message
PPercent_inc := PChar( @InputBuffer [meta.getOffset( status, 0 )] );
PDept_no := PChar( @InputBuffer [meta.getOffset( status, 1 )] );
For i := 0 To length( Dept_Data ) - 1 Do Begin
If ( Dept_Data [i] = '0' ) Or ( Percent_data [i] = 0 ) Then
break;
StrPCopy( PPercent_inc, Percent_data [i].ToString );
StrPCopy( PDept_no, Dept_Data [i] );
WriteLn( 'Increasing budget for department: ' + PDept_no + ' by ' + PPercent_inc + ' percent.' );
Try
stmt.Execute( status, tra, meta, @InputBuffer, nil, nil );
// Save/Cancel each department's update independently.
// *** Change to commitRetaining() to see changes
// *** tra.commitRetaining(status);
tra.rollbackRetaining( status );
Except
on E: FBException Do Begin
PrintError( master, status );
tra.rollbackRetaining( status );
End;
End;
End;
stmt.Free( status );
stmt := nil;
meta.Release;
meta := nil;
tra.commit( status );
tra := nil;
att.detach( status );
att := nil;
Except
on E: FBException Do Begin
PrintError( master, status );
tra.rollbackRetaining( status );
End;
on E: Exception Do
WriteLn( E.Message );
End;
Finally
If assigned( meta ) Then
meta.Release;
If assigned( builder ) Then
builder.Release;
If assigned( stmt ) Then
stmt.Release;
If assigned( tra ) Then
tra.Release;
If assigned( att ) Then
att.Release;
prov.Release;
status.dispose;
End;
End.