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Implemented in Osm Admin:

• new ALTER TABLE algorithm
• NULL to non-NULL data conversion
• new query test suite

This time, I tackled adding an explicit property to an existing table, and then making it non-nullable.

It raised the need for data conversions - additional handling of the existing data - or otherwise, the database engine fails, or the data becomes invalid.

And it made me split migrations in two parts - the one that runs before the data conversion, and the other one that runs afterwards.

While working on diff algorithm I noticed a certain pattern that I use over an over again.

Using this pattern, I implemented notification table diff.

Finally, I rearranged diff/migration code for better code readability.

Yesterday, I moved the table creation code into new schema diff migration engine.

Now, working on notification table migrations.

This time:

• I found out that the whole search index creation should be done during indexing, not migrations.
• I refactored diff algorithm and made it much easier to read.

Before digging into property diff algorithm, let's dig into how exactly it's used, and what other property-related logic is there.

Yesterday, I continued working on schema migrations:

• implemented table diff algorithm;
• took into consideration table renames.

After a system update, I've got some problem with my laptop, and one thing to check was system log files.

This got me thinking: what makes a good log for my own application? And I think that application logs are as useful as they are able to answer potential questions I may have when an application is in production.

Let's think what kind of questions I might have, and what information might be useful to answer them.

Recently, I fixed numerous issues to make the first migration tests work.

Then, I started implementing the schema diff algorithm - the basis for schema migrations.

More dots got connected in the schema migration design, see this post for details.

Then, I tried to return to TDDing it, but strange errors met me there, so I left them to be resolved in the next piece.

Schema migrations are going to be generated and executed automatically under gulp watch. It will result in lots of tiny migrations: add a column, change its type, make it not nullable, and so on.

It's convenient during development, but it might be not optimal to reapply in production. Indeed, it's better to convert a large table to new structure all at once rather than running a conversion for each of the tiny migration.

This observation contradicts the previously stated migration workflow, so let's update it.

In spirit of TDD, I started with a meaningful, but failing test that is reasonably fast. Then, I worked to make it green:

• implemented the loading of schema fixtures from the codebase;
• worked on generating migration files.

After drafting some ideas of how the schema migrations should actually work, let's start implementing it in TDD way.

The goal of the current iteration is to adjust the database schema and preserve/convert existing data according to any changes in schema classes, grids, forms or indexers.

This post presents some thoughts how it might work with class definitions.

After finishing the iteration "#17 Minimum UI", I revisited the goals and the scope of the minimum viable product, and picked the most pressing task for the next iteration - "#18 Database Schema Changes".

I implemented the last user action that is typical to a CRUD application - object deletion.

Done:

• routes responsible for creating new products, and modifying existing products
• incremental indexing
• cloning query objects
• INSERT INTO ... SELECT ... statements