5 Useful MySQL SQL Performance Tuning Recommendations

Like everything else, indexes also come with a few shortcomings of their own. However, this post will focus on query optimization while considering both situations - those that contain table indexes and those without.

An indication of good MySQL SQL performance tuning is the inclusion of detailed analysis that covers each statement per database instance. Furthermore, it should view all the tables getting accessed during query execution and suggest table tuning in case of positive effects.

It is necessary to observe the effects on every statement manipulating the table instead of a specific query. Experts have noticed basic table index recommendations enhance Oracle SQL performance by 100% for individual queries while improving query performance for other statements using the same table, leading to improvement of as low as 12% to a high as a three-digit enhancement.

With that, consider the following suggestions that can prove useful during Oracle SQL Performance tuning and optimization, when it comes to indexes.

The first one involves the assessment of overlapping indexes. Indexes overlap when they have a commonly defined first column. Since each index comes with a disk space requirement and maintenance expense, it helps if you identify and eliminate unnecessary indexes during MySQL SQL performance tuning.

Analyze overlapping indexes to ascertain whether getting rid of any of them helps performance. For instance, if two indexes have identical columns in an identical order as well, but one of the indexes has extra columns, you can remove the smaller index as it is redundant.

Or, if two indexes contain identical columns but both have one or more additional columns, you may choose to include the additional columns of one of the indexes into the other and eliminate the first index.

Wide Indexes are also worth observation. Indexes are said to be wide when they fulfil one or more of the following criteria:

●       It has five or more columns

●       It has a capacity of over 200 bytes

The bigger an index the more storage - and subsequently, maintenance - it needs. Indexes fulfilling the first condition could be covering indexes for more than one query but the enhancement in performance could counterbalance extra expenses.

On the other hand, the opposite is true if the index isn’t a covering index - that is, it may cost more to maintain the index than the performance boost it will provide. Eliminating trailing edge columns helps in such situations.

When there aren’t any defined indexes in a table, its size affects the usefulness of adding one. If the table is large, for instance, you may want to add an index but for smaller tables, a full table scan will usually be sufficient.

Also, tables that lack primary keys should be given an artificial primary key such as a serial number column. That’s because a primary key is not only vital for joining tables but it is also important to ensure data integrity.

Tables containing foreign keys are generally child tables since a foreign key refers to the parent table’s primary key. If each of those foreign keys is indexed, it can boost MySQL SQL performance, regardless of whether you’re using a SQL query optimization tool, particularly for statements written to join two tables. If a foreign key isn’t indexed, a full table scan becomes inevitable every time a row is removed or the parent table’s primary key value is updated.

Although the tips given above will benefit the performance of a majority of queries, certain index-related adjustments may have their own consequences. One of these is the rise in index maintenance cost with the rise in the amount of data churn. For instance, every time a row is added, removed or modified, the index will be updated accordingly, which will also add to the time it takes for the respective action.

Additionally, bigger tables that contain more columns in the index will require greater amounts of storage space. Despite this, storage costs can be expected to decrease and are usually not thought of as an obstacle to carrying out indexing tips.