REGEXP for SQLite

Since SQLite does not define a regexp function by default, provide a Qt
based implementation which can be enabled using QSQLITE_ENABLE_REGEXP as
an connect option. This way statements like

SELECT * FROM table WHERE col REGEXP '^[a-d]';

work out of the box.

[ChangeLog][QtSql] Add QSQLITE_ENABLE_REGEXP connect option for
QSQLiteDriver. If set a Qt based regexp() implementation is provided
allowing to use REGEXP in SQL statements.

Task-number: QTBUG-18084
Change-Id: I7f0e926fe4c5d6baea509f75497f46a61ca86679
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>
Reviewed-by: Jesus Fernandez <Jesus.Fernandez@qt.io>
Reviewed-by: Sebastian Sauer <sebastian.sauer@kdab.com>
Reviewed-by: Andy Shaw <andy.shaw@qt.io>
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/sql/doc/src/sql-driver.qdoc b/src/sql/doc/src/sql-driver.qdoc
index 364d733e92..57a53006c4 100644
--- a/src/sql/doc/src/sql-driver.qdoc
+++ b/src/sql/doc/src/sql-driver.qdoc
@@ -568,6 +568,22 @@
 
     \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.