Is it better to create an index before filling a table with data, or after the data is in place?

sql

index-creation

database-performance

data-loading

byAlex Kataev·Oct 16, 2024

Index after data load for bulk inserts; it's quicker; indexes don't rebuild on each entry. For incremental updates, timely indexing optimizes query performance.

SQL snippet:

-- Here we go, Mr.Index is making his entrance!
CREATE INDEX idx_your_column ON your_table(your_column);
-- Even indexes can't skip the queue.

When handling large datasets, efficiency of index operations is vital. It's generally quicker and efficient to create indexes after inserting the data.

Index creation & data volume

Consider the size of your tables. For small to medium-sized tables, an index before data insertion isn't fatal. But for very large datasets (100M+ rows), dropping the existing index beforehand and recreating it after data loading is the way to go.

Index efficiency & the need for speed

It’s not always about speed. Look at the big picture; overall efficiency of the system is crucial. Prioritize performance over speed of record insertion. This takes into account the index’s rebuild time and the gain in query performance.

DBMS-specifics

Match your DBMS

Many aspects depend on your actual DBMS; MySQL, PostgreSQL, SQL Server and others have their own unique takes on indexing.

Experiment & optimize

There's no one-size-fits-all; test different methods against your data to come up with the best indexing method.

Handle Full-text indexing

Be conscious of full-text indexes on large VARCHAR fields. It can impact your match performance if not handled correctly.

Check # Post-creation performance

Once created, don't set and forget! Regularly look into your index’s balance and effectiveness. Ensuring this regularly can optimize the overall performance.

Considerations in index handling

Clever drop & recreate

With large tables, strategically dropping and re-creating index can significantly boost performance.

Import speeds & Indexing

Indexing consumes time and slows down imports. If your imports are massive, consider creating indexes after data loading.

Cater to transactional loads

In high transactional systems, index creation strategy should be tight. There, incremental indexing or using selective indexing approaches can be crucial.

Alter wisely

For expecting a diverse range of data, altering table structure beforehand can be beneficial. This can boost index efficiency, but tread carefully as it may also lead to performance issues.

explain-codes / Sql / Is it better to create an index before filling a table with data, or after the data is in place?

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