1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
|
<!DOCTYPE html>
<html lang="en" data-bs-theme="light">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="shortcut icon" href="../img/favicon.ico">
<title>Connections - SOCI (4.1.2)</title>
<link href="../css/bootstrap.min.css" rel="stylesheet">
<link href="../css/fontawesome.min.css" rel="stylesheet">
<link href="../css/brands.min.css" rel="stylesheet">
<link href="../css/solid.min.css" rel="stylesheet">
<link href="../css/v4-font-face.min.css" rel="stylesheet">
<link href="../css/base.css" rel="stylesheet">
<link id="hljs-light" rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.8.0/styles/github.min.css" >
<link id="hljs-dark" rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.8.0/styles/github-dark.min.css" disabled>
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.8.0/highlight.min.js"></script>
<script>hljs.highlightAll();</script>
</head>
<body>
<div class="navbar fixed-top navbar-expand-lg navbar-dark bg-primary">
<div class="container">
<a class="navbar-brand" href="..">SOCI (4.1.2)</a>
<!-- Expander button -->
<button type="button" class="navbar-toggler" data-bs-toggle="collapse" data-bs-target="#navbar-collapse" aria-controls="navbar-collapse" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<!-- Expanded navigation -->
<div id="navbar-collapse" class="navbar-collapse collapse">
<!-- Main navigation -->
<ul class="nav navbar-nav">
<li class="nav-item">
<a href=".." class="nav-link">Home</a>
</li>
<li class="nav-item dropdown">
<a href="#" class="nav-link dropdown-toggle" role="button" data-bs-toggle="dropdown" aria-expanded="false">Overview</a>
<ul class="dropdown-menu">
<li>
<a href="../quickstart/" class="dropdown-item">Getting Started</a>
</li>
<li>
<a href="../installation/" class="dropdown-item">Installation</a>
</li>
<li>
<a href="../structure/" class="dropdown-item">Library Structure</a>
</li>
<li>
<a href="../license/" class="dropdown-item">License</a>
</li>
<li>
<a href="../faq/" class="dropdown-item">FAQ</a>
</li>
</ul>
</li>
<li class="nav-item dropdown">
<a href="#" class="nav-link dropdown-toggle active" aria-current="page" role="button" data-bs-toggle="dropdown" aria-expanded="false">User Guide</a>
<ul class="dropdown-menu">
<li>
<a href="./" class="dropdown-item active" aria-current="page">Connections</a>
</li>
<li>
<a href="../queries/" class="dropdown-item">Queries</a>
</li>
<li>
<a href="../binding/" class="dropdown-item">Data Binding</a>
</li>
<li>
<a href="../indicators/" class="dropdown-item">Data Indicators</a>
</li>
<li>
<a href="../types/" class="dropdown-item">Data Types</a>
</li>
<li>
<a href="../lobs/" class="dropdown-item">LOBs</a>
</li>
<li>
<a href="../statements/" class="dropdown-item">Statements</a>
</li>
<li>
<a href="../transactions/" class="dropdown-item">Transactions</a>
</li>
<li>
<a href="../procedures/" class="dropdown-item">Procedures</a>
</li>
<li>
<a href="../errors/" class="dropdown-item">Errors</a>
</li>
<li>
<a href="../logging/" class="dropdown-item">Logging</a>
</li>
<li>
<a href="../interfaces/" class="dropdown-item">Interfaces</a>
</li>
</ul>
</li>
<li class="nav-item dropdown">
<a href="#" class="nav-link dropdown-toggle" role="button" data-bs-toggle="dropdown" aria-expanded="false">Backends</a>
<ul class="dropdown-menu">
<li>
<a href="../backends/" class="dropdown-item">Features</a>
</li>
<li>
<a href="../backends/db2/" class="dropdown-item">DB2</a>
</li>
<li>
<a href="../backends/firebird/" class="dropdown-item">Firebird</a>
</li>
<li>
<a href="../backends/mysql/" class="dropdown-item">MySQL</a>
</li>
<li>
<a href="../backends/odbc/" class="dropdown-item">ODBC</a>
</li>
<li>
<a href="../backends/oracle/" class="dropdown-item">Oracle</a>
</li>
<li>
<a href="../backends/postgresql/" class="dropdown-item">PostgreSQL</a>
</li>
<li>
<a href="../backends/sqlite3/" class="dropdown-item">SQLite3</a>
</li>
</ul>
</li>
<li class="nav-item dropdown">
<a href="#" class="nav-link dropdown-toggle" role="button" data-bs-toggle="dropdown" aria-expanded="false">Miscellaneous</a>
<ul class="dropdown-menu">
<li>
<a href="../beyond/" class="dropdown-item">Beyond SQL</a>
</li>
<li>
<a href="../multithreading/" class="dropdown-item">Multi-threading</a>
</li>
<li>
<a href="../boost/" class="dropdown-item">Boost</a>
</li>
<li>
<a href="../utilities/" class="dropdown-item">Utilities</a>
</li>
<li>
<a href="../vagrant/" class="dropdown-item">Vagrant</a>
</li>
</ul>
</li>
<li class="nav-item dropdown">
<a href="#" class="nav-link dropdown-toggle" role="button" data-bs-toggle="dropdown" aria-expanded="false">API</a>
<ul class="dropdown-menu">
<li>
<a href="../api/client/" class="dropdown-item">Client API</a>
</li>
<li>
<a href="../api/backend/" class="dropdown-item">Backend API</a>
</li>
<li class="dropdown-submenu">
<a href="#" class="dropdown-item">Ada</a>
<ul class="dropdown-menu">
<li>
<a href="../languages/ada/" class="dropdown-item">Ada Bindings</a>
</li>
<li>
<a href="../languages/ada/concepts/" class="dropdown-item">Ada Concepts</a>
</li>
<li>
<a href="../languages/ada/idioms/" class="dropdown-item">Ada Idioms</a>
</li>
<li>
<a href="../languages/ada/reference/" class="dropdown-item">Ada API Reference</a>
</li>
</ul>
</li>
</ul>
</li>
</ul>
<ul class="nav navbar-nav ms-md-auto">
<li class="nav-item">
<a href="#" class="nav-link" data-bs-toggle="modal" data-bs-target="#mkdocs_search_modal">
<i class="fa fa-search"></i> Search
</a>
</li>
<li class="nav-item">
<a rel="prev" href="../faq/" class="nav-link">
<i class="fa fa-arrow-left"></i> Previous
</a>
</li>
<li class="nav-item">
<a rel="next" href="../queries/" class="nav-link">
Next <i class="fa fa-arrow-right"></i>
</a>
</li>
<li class="nav-item">
<a href="https://github.com/SOCI/soci/edit/master/docs/connections.md" class="nav-link"><i class="fa-brands fa-github"></i> Edit on GitHub</a>
</li>
</ul>
</div>
</div>
</div>
<div class="container">
<div class="row">
<div class="col-md-3"><div class="navbar-expand-md bs-sidebar hidden-print affix" role="complementary">
<div class="navbar-header">
<button type="button" class="navbar-toggler collapsed" data-bs-toggle="collapse" data-bs-target="#toc-collapse" title="Table of Contents">
<span class="fa fa-angle-down"></span>
</button>
</div>
<div id="toc-collapse" class="navbar-collapse collapse card bg-body-tertiary">
<ul class="nav flex-column">
<li class="nav-item" data-bs-level="1"><a href="#connections" class="nav-link">Connections</a>
<ul class="nav flex-column">
<li class="nav-item" data-bs-level="2"><a href="#using-backend-factory" class="nav-link">Using backend factory</a>
<ul class="nav flex-column">
</ul>
</li>
<li class="nav-item" data-bs-level="2"><a href="#using-loadable-backends" class="nav-link">Using loadable backends</a>
<ul class="nav flex-column">
</ul>
</li>
<li class="nav-item" data-bs-level="2"><a href="#using-registered-backends" class="nav-link">Using registered backends</a>
<ul class="nav flex-column">
</ul>
</li>
<li class="nav-item" data-bs-level="2"><a href="#connection-failover" class="nav-link">Connection failover</a>
<ul class="nav flex-column">
</ul>
</li>
</ul>
</li>
</ul>
</div>
</div></div>
<div class="col-md-9" role="main">
<h1 id="connections">Connections</h1>
<p>The <code>session</code> class encapsulates the database connection and other backend-related details, which are common to all the statements that will be later executed. It has a couple of overloaded constructors.</p>
<h2 id="using-backend-factory">Using backend factory</h2>
<p>The most basic one expects two parameters: the requested backend factory object and the generic connection string,
which meaning is backend-dependent.</p>
<p>Example:</p>
<pre><code class="language-cpp">session sql(oracle, "service=orcl user=scott password=tiger");
</code></pre>
<p>Another example might be:</p>
<pre><code class="language-cpp">session sql(postgresql, "dbname=mydb");
</code></pre>
<p>Above, the <code>sql</code> object is a local (automatic) object that encapsulates the connection.</p>
<p>This <code>session</code> constructor either connects successfully, or throws an exception.</p>
<h3 id="portability-note">Portability note</h3>
<p>In case of SOCI linked against DLLs on Windows, the factory objects are not exported from the DLLs.
In order to avoid linker errors, access factory objects via dedicated backend functions
provided (eg. <code>factory_postgresql()</code>).</p>
<h2 id="using-loadable-backends">Using loadable backends</h2>
<p>Dynamically loadable backends are compiled as shared libraries and allow to select backends at run-time by name.</p>
<p>The usage is similar to the above, but instead of providing the factory object, the backend name is expected:</p>
<pre><code class="language-cpp">session sql("postgresql", "dbname=mydb");
</code></pre>
<p>For convenience, the URL-like form that combines both the backend name with connection parameters is supported as well:</p>
<pre><code class="language-cpp">session sql("postgresql://dbname=mydb");
</code></pre>
<p>The last two constructors described above try to locate the shared library with the name <code>libsoci_ABC.so</code> (or <code>libsoci_ABC.dll</code> on Windows), where ABC is the backend name.
In the above examples, the expected library name will be <code>libsoci_postgresql.so</code> for Unix-like systems.</p>
<p>The most general form of the constructor takes a single object of <code>connection_parameters</code> type which contains a pointer to the backend to use, the connection string and also any connection options.
Using this constructor is the only way to pass any non-default options to the backend.</p>
<p>For example, to suppress any interactive prompts when using ODBC backend you could do:</p>
<pre><code class="language-cpp">connection_parameters parameters("odbc", "DSN=mydb");
parameters.set_option(odbc_option_driver_complete, "0" /* SQL_DRIVER_NOPROMPT */);
session sql(parameters);
</code></pre>
<p>Notice that you need to <code>#include<soci-odbc.h></code> to obtain the option name declaration.
The existing options are described in the backend-specific part of the documentation.</p>
<p>IBM DB2 driver for ODBC and CLI also support the driver completion requests.
So, the DB2 backend provides similar option <code>db2_option_driver_complete</code> with <code>#include <soci-db2.h></code> required to obtain the option name.</p>
<h3 id="environment-configuration">Environment configuration</h3>
<p>The <code>SOCI_BACKENDS_PATH</code> environment variable defines the set of paths where the shared libraries will be searched for.
There can be many paths, separated by colons, and they are used from left to right until the library with the appropriate name is found. If this variable is not set or is empty, the current directory is used as a default path for dynamically loaded backends.</p>
<h2 id="using-registered-backends">Using registered backends</h2>
<p>The run-time selection of backends is also supported with libraries linked statically.</p>
<p>Each backend provides a separate function of the form <code>register_factory_*name*</code>, where <code>*name*</code> is a backend name. Thus:</p>
<pre><code class="language-cpp">extern "C" void register_factory_postgresql();
// ...
register_factory_postgresql();
session sql("postgresql://dbname=mydb");
</code></pre>
<p>The above example registers the backend for PostgreSQL and later creates the session object for that backend.
This form is provided for those projects that prefer static linking but still wish to benefit from run-time backend selection.</p>
<p>An alternative way to set up the session is to create it in the disconnected state and connect later:</p>
<pre><code class="language-cpp">session sql;
// some time later:
sql.open(postgresql, "dbname=mydb");
// or:
sql.open("postgresql://dbname=mydb");
// or also:
connection_parameters parameters("postgresql", "dbname=mydb");
sql.open(parameters);
</code></pre>
<p>The rules for backend naming are the same as with the constructors described above.</p>
<p>The session can be also explicitly <code>close</code>d and <code>reconnect</code>ed, which can help with basic session error recovery, e.g. the application could check if <code>is_connected</code> still returns true after getting an error and attempt to call <code>reconnect</code> if it doesn't.
The <code>reconnect</code> function has no parameters and attempts to use the same values as those provided with earlier constructor or <code>open</code> calls.</p>
<p>See also the page devoted to <a href="../multithreading/">multithreading</a> for a detailed description of connection pools.</p>
<p>It is possible to have many active <code>session</code>s at the same time, even using different backends.</p>
<h3 id="portability-note_1">Portability note</h3>
<p>The following backend factories are currently (as of 3.1.0 release) available:</p>
<ul>
<li><a href="../backends/mysql/">mysql</a> (requires <code>#include "soci-mysql.h"</code>)</li>
<li><a href="../backends/oracle/">oracle</a> (requires <code>#include "soci-oracle.h"</code>)</li>
<li><a href="../backends/postgresql/">postgresql</a> (requires <code>#include "soci-postgresql.h"</code>)</li>
</ul>
<p>The following backends are also available, with various levels of completeness:</p>
<ul>
<li><a href="../backends/sqlite3/">sqlite3</a> (requires <code>#include "soci-sqlite3.h"</code>)</li>
<li><a href="../backends/odbc/">odbc</a> (requires <code>#include "soci-odbc.h"</code>)</li>
<li><a href="../backends/firebird/">firebird</a> (requires <code>#include "soci-firebird.h"</code>)</li>
<li><a href="../backends/db2/">db2</a> (requires <code>#include "soci-db2.h"</code>)</li>
</ul>
<h2 id="connection-failover">Connection failover</h2>
<p>The <code>failover_callback</code> interface can be used as a callback channel for notifications of events that are automatically processed when the session is forcibly closed due to connectivity problems. The user can override the following methods:</p>
<pre><code class="language-cpp">// Called when the failover operation has started,
// after discovering connectivity problems.
virtual void started();
// Called after successful failover and creating a new connection;
// the sql parameter denotes the new connection and allows the user
// to replay any initial sequence of commands (like session configuration).
virtual void finished(session & sql);
// Called when the attempt to reconnect failed,
// if the user code sets the retry parameter to true,
// then new connection will be attempted;
// the newTarget connection string is a hint that can be ignored
// by external means.
virtual void failed(bool & retry, std::string & newTarget);
// Called when there was a failure that prevents further failover attempts.
virtual void aborted();
</code></pre>
<p>The user-provided callback implementation can be installed (or reset) with:</p>
<pre><code class="language-cpp">sql.set_failover_callback(myCallback);
</code></pre>
<h3 id="portability-note_2">Portability note</h3>
<p>The <code>failover_callback</code> functionality is currently supported only by PostgreSQL and Oracle backends (in the latter case the failover mechanism is governed by the Oracle-specific cluster configuration settings).
Other backends allow the callback object to be installed, but will ignore it and will not generate notification calls.</p></div>
</div>
</div>
<footer class="col-md-12">
<hr>
<p>Copyright © 2017-2025 <a href="https://soci.sourceforge.net/people.html">SOCI Team</a>.</p>
<p>Documentation built with <a href="https://www.mkdocs.org/">MkDocs</a>.</p>
</footer>
<script src="../js/bootstrap.bundle.min.js"></script>
<script>
var base_url = "..",
shortcuts = {"help": 191, "next": 78, "previous": 80, "search": 83};
</script>
<script src="../js/base.js"></script>
<script src="../search/main.js"></script>
<div class="modal" id="mkdocs_search_modal" tabindex="-1" role="dialog" aria-labelledby="searchModalLabel" aria-hidden="true">
<div class="modal-dialog modal-lg">
<div class="modal-content">
<div class="modal-header">
<h4 class="modal-title" id="searchModalLabel">Search</h4>
<button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
</div>
<div class="modal-body">
<p>From here you can search these documents. Enter your search terms below.</p>
<form>
<div class="form-group">
<input type="search" class="form-control" placeholder="Search..." id="mkdocs-search-query" title="Type search term here">
</div>
</form>
<div id="mkdocs-search-results" data-no-results-text="No results found"></div>
</div>
<div class="modal-footer">
</div>
</div>
</div>
</div><div class="modal" id="mkdocs_keyboard_modal" tabindex="-1" role="dialog" aria-labelledby="keyboardModalLabel" aria-hidden="true">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<h4 class="modal-title" id="keyboardModalLabel">Keyboard Shortcuts</h4>
<button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
</div>
<div class="modal-body">
<table class="table">
<thead>
<tr>
<th style="width: 20%;">Keys</th>
<th>Action</th>
</tr>
</thead>
<tbody>
<tr>
<td class="help shortcut"><kbd>?</kbd></td>
<td>Open this help</td>
</tr>
<tr>
<td class="next shortcut"><kbd>n</kbd></td>
<td>Next page</td>
</tr>
<tr>
<td class="prev shortcut"><kbd>p</kbd></td>
<td>Previous page</td>
</tr>
<tr>
<td class="search shortcut"><kbd>s</kbd></td>
<td>Search</td>
</tr>
</tbody>
</table>
</div>
<div class="modal-footer">
</div>
</div>
</div>
</div>
</body>
</html>
|