Generating db patches with DiffKit

In the 0.8.7 release, DiffKit gained the ability to generate database "patches". These patches are analogous to the patch files produced by traditional *nix diff tools-- they can be read by a patching tool in order to edit the RHS so that it is identical to the LHS.

Table 1. DiffKit versus Diffutils

	diff tool	patch format	patch tool
DiffKit	diffkit-app	sql DML	any DML applicator
Diffutils	diff	unidiff	patch

The "patch" files produced by DiffKit contain only INSERT, DELETE, and UPDATE statements. After the user applies those DML statements to the RHS table, using whichever tools and techniques they prefer, the RHS table will have identical contents to the LHS table. The DiffKit application will never directly modify your tables-- DiffKit is strictly a read-only application from the perspective of your table data.

DB patches are created by using a new Sink implementation: the SqlPatchSink. test26.plan.xml, in the eg/ (examples) folder, dmonstrates this:

test26.plan.xml

   ...
      <property name="sqlPatchFilePath" value="./test26.sink.patch" />
   ...

invoked this way:

java -jar ../diffkit-app.jar -planfiles test26.plan.xml,dbConnectionInfo.xml

produces this output in the patch file:

test26.sink.patch

DELETE FROM PUBLIC.TEST26_RHS_TABLE
WHERE (COLUMN1='1' );

INSERT INTO PUBLIC.TEST26_RHS_TABLE (COLUMN1, COLUMN2, COLUMN3, COLUMN4)
VALUES ('2', 'xxxx', 2, 'zz2zz');

UPDATE PUBLIC.TEST26_RHS_TABLE
SET COLUMN3=3
WHERE (COLUMN1='3' );

UPDATE PUBLIC.TEST26_RHS_TABLE
SET COLUMN2='5555', COLUMN3=4, COLUMN4='zz4zz'
WHERE (COLUMN1='4' );

INSERT INTO PUBLIC.TEST26_RHS_TABLE (COLUMN1, COLUMN2, COLUMN3, COLUMN4)
VALUES ('5', 'xxxx', 5, 'zz5zz');

DELETE FROM PUBLIC.TEST26_RHS_TABLE
WHERE (COLUMN1='6' );