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Displaying posts with tag: virtual_columns (reset)
Creating JSON documents with MariaDB

You probably know about two MariaDB great features: Dynamic Columns and Virtual Colums. I don’t think that we already found all possible use cases for them: more ideas will come in the future, and hopefully someone will write about them. Here, I will describe a use case which involves both Virtual Columns and Dynamic Columns.

Now, suppose that we have relational data in MariaDB, and we want to periodically export them in JSON, so we can export them to a variety of other data sources. For most data format, the best exporting solution is generally the CONNECT storage engine; but …

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Descending indexes in MariaDB

Since the dawn of time, MySQL indexes have a limit: they cannot be descending. Yes, ALTER TABLE and CREATE INDEX can contain the ASC and DESC keywords. It is perfectly legal in MySQL. But this does not mean that descending indexes are created. This is a well-known MySQL feature: when it cannot do something, it just pretends to. Well… someone thinks it is a feature. I think it is a bug (a bug is an unexpected behaviour), but what can we do.

The lack of support for descending indexes is only an issue when we need to create an index in which at least one column is ascending and at least one column is descending. For example, MySQL pretends to understand the following statement, but the resulting index won’t probably help us:

CREATE INDEX my_index ON my_table (my_column ASC, your_column DESC);

An ORDER BY my_column ASC, your_column DESC won’t …

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