From 1dab2da7c969e328281765d59d2fe90d618fadc6 Mon Sep 17 00:00:00 2001 From: Boris Kolpackov Date: Wed, 2 Nov 2011 14:29:23 +0200 Subject: Add example for optimistic concurrency support --- optimistic/README | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 optimistic/README (limited to 'optimistic/README') diff --git a/optimistic/README b/optimistic/README new file mode 100644 index 0000000..4c38e66 --- /dev/null +++ b/optimistic/README @@ -0,0 +1,56 @@ +This example shows how to use optimistic concurrency in ODB. + +The example consists of the following files: + +person.hxx + Header file defining the 'person' persistent class. Besides the standard + persistent class pragmas, this definition also uses the 'optimistic' + pragma to indicate to the ODB compiler that the class must support + optimistic concurrency. It also uses the 'version' pragma to specify + which data member will contain the object version. + +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 and persists a sample 'person' object. It then emulates the + parallel execution of two processes that try to concurrently update or + delete this object. For each step the driver prints the versions of the + object as seen by each process. + +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