From 22cb56f4a1ad5d2c6d581bab5e528a0cf0d13b17 Mon Sep 17 00:00:00 2001 From: Boris Kolpackov Date: Wed, 14 Aug 2013 15:16:09 +0200 Subject: Add support for object sections Sections are an optimization mechanism that allows the partitioning of data members of a persistent class into groups that can be separately loaded and/or updated. --- section/README | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 section/README (limited to 'section/README') diff --git a/section/README b/section/README new file mode 100644 index 0000000..34be589 --- /dev/null +++ b/section/README @@ -0,0 +1,63 @@ +This example shows how to use object sections to implement lazy-loading +and change-updating of a subset of data members in a persistent class. + +The example consists of the following files: + +person.hxx + Header file defining the 'person' persistent class. It contains a number of + data members some of which are made to belong to a section. + +person-odb.hxx +person-odb.ixx +person-odb.cxx +person.sql + The first three files contain the database support code and the last file + contains the database schema for the person.hxx header. + + These files are generated by the ODB compiler from person.hxx using the + following command line: + + odb -d --generate-schema person.hxx + + Where stands for the database system we are using, for example, + 'mysql'. + +database.hxx + Contains the create_database() function which instantiates the concrete + database class corresponding to the database system we are using. + +driver.cxx + Driver for the example. It includes the person.hxx and person-odb.hxx + headers to gain access to the persistent classes and their database support + code. It also includes database.hxx for the create_database() function + declaration. + + In main() the driver first calls create_database() to obtain the database + instance. It then persists a 'person' object, loads it back, including + the section, and prints the contents of its members. Finally, the driver + shows how to update the state of the section data members in various ways, + then re-loads and prints the object to verify that the changes have been + made persistent. + +To compile and link the example manually from the command line we can use +the following commands (using MySQL as an example; replace 'c++' with your +C++ compiler name): + +c++ -c person-odb.cxx +c++ -DDATABASE_MYSQL -c driver.cxx +c++ -o driver driver.o person-odb.o -lodb-mysql -lodb + +To run the example we may first need to create the database schema (for some +database systems, such as SQLite, the schema is embedded into the generated +code which makes this step unnecessary). Using MySQL as an example, this +can be achieved with the following command: + +mysql --user=odb_test --database=odb_test < person.sql + +Here we use 'odb_test' as the database login and also 'odb_test' as the +database name. + +Once the database schema is ready, we can run the example (using MySQL as +the database): + +./driver --user odb_test --database odb_test -- cgit v1.1