diff options
Diffstat (limited to 'src/sql/doc/src')
| -rw-r--r-- | src/sql/doc/src/sql-driver.qdoc | 63 |
1 files changed, 62 insertions, 1 deletions
diff --git a/src/sql/doc/src/sql-driver.qdoc b/src/sql/doc/src/sql-driver.qdoc index c8de78dd79..fd95e89812 100644 --- a/src/sql/doc/src/sql-driver.qdoc +++ b/src/sql/doc/src/sql-driver.qdoc @@ -299,6 +299,12 @@ e.g., the SQLSTATEs. Before setting this connect option, consult your ODBC documentation about behavior differences you can expect. + When using the SAP HANA database, the connection has to be + established using the option "SCROLLABLERESULT=TRUE", as the + HANA ODBC driver does not provide scrollable results by default, e.g.: + + \snippet code/doc_src_sql-driver.cpp 39 + If you experience very slow access of the ODBC datasource, make sure that ODBC call tracing is turned off in the ODBC datasource manager. @@ -380,6 +386,45 @@ Binary Large Objects are supported through the \c BYTEA field type in PostgreSQL server versions >= 7.1. + \section3 QPSQL Forward-only query support + + To use forward-only queries, you must build the QPSQL plugin with + PostreSQL client library version 9.2 or later. If the plugin is + built with an older version, then forward-only mode will not be + available - calling QSqlQuery::setForwardOnly() with \c true will + have no effect. + + \warning If you build the QPSQL plugin with PostgreSQL version 9.2 or later, + then you must distribute your application with libpq version 9.2 or later. + Otherwise, loading the QPSQL plugin will fail with the following message: + + \snippet code/doc_src_sql-driver.qdoc 35 + + While navigating the results in forward-only mode, the handle of + QSqlResult may change. Applications that use the low-level handle of + SQL result must get a new handle after each call to any of QSqlResult + fetch functions. Example: + + \snippet code/doc_src_sql-driver.cpp 36 + + While reading the results of a forward-only query with PostgreSQL, + the database connection cannot be used to execute other queries. + This is a limitation of libpq library. Example: + + \snippet code/doc_src_sql-driver.cpp 37 + + This problem will not occur if query1 and query2 use different + database connections, or if we execute query2 after the while loop. + + \note Some methods of QSqlDatabase like tables(), primaryIndex() + implicity execute SQL queries, so these also cannot be used while + navigating the results of forward-only query. + + \note QPSQL will print the following warning if it detects a loss of + query results: + + \snippet code/doc_src_sql-driver.qdoc 38 + \section3 How to Build the QPSQL Plugin on Unix and \macos You need the PostgreSQL client library and headers installed. @@ -404,7 +449,7 @@ \target QTDS \section2 QTDS for Sybase Adaptive Server - \note TDS is no longer used by MS Sql Server, and is superceded by + \note TDS is no longer used by MS Sql Server, and is superseded by \l{QODBC}{ODBC}. QTDS is obsolete from Qt 4.7. It is not possible to set the port with QSqlDatabase::setPort() due to limitations in the @@ -534,6 +579,22 @@ \snippet code/doc_src_sql-driver.qdoc 23 + \section3 Enable REGEXP operator + + SQLite comes with a REGEXP operation. However the needed implementation must + be provided by the user. For convenience a default implementation can be + enabled by \l{QSqlDatabase::setConnectOptions()} {setting the connect + option} \c{QSQLITE_ENABLE_REGEXP} before \l{QSqlDatabase::open()} {the + database connection is opened}. Then a SQL statement like "column REGEXP + 'pattern'" basically expands to the Qt code + + \snippet code/doc_src_sql-driver.cpp 34 + + For better performance the regular expressions are cached internally. By + default the cache size is 25, but it can be changed through the option's + value. For example passing "\c{QSQLITE_ENABLE_REGEXP=10}" reduces the + cache size to 10. + \section3 QSQLITE File Format Compatibility SQLite minor releases sometimes break file format forward compatibility. |