How to Safely Perform Backfill Operations in TimescaleDB

Backfilling data into a TimescaleDB hypertable in production can be very tricky, especially when automated processes like compression policies are involved. From past experience, we have seen that if backfill operations aren’t handled properly, they can interfere with these automated tasks, sometimes causing them to stop working altogether. This blog covers a safer and more reliable approach to backfilling hypertables, along with best practices to prevent disruptions to compression and other background processes.What is a Backfill Operation?Backfilling means adding old or missing data into the database table after some time has already passed. Imagine you are collecting temperature readings every hour, but your system was down for a day and didn’t save any data. Later, you get that missing data from the local storage of the device or cloud storage, and want to put it back in the right hypertable, which is called backfilling. In TimescaleDB, this is common with time-series data, but it needs to be done carefully. That’s because TimescaleDB might already be doing things in the background, like compressing old data to save space. If we are not careful, backfilling can mess up these automatic tasks.
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Improving PostgreSQL Performance with Partitioning

My recommended methodology for performance improvement of PostgreSQL starts with query optimization. The second step is architectural improvements, part of which is the partitioning of large tables.Partitioning in PostgreSQL is one of those advanced features that can be a powerful performance booster. If your PostgreSQL tables are becoming very large and sluggish, partitioning might be the cure.The Big Table ProblemLarge tables tend to grow uncontrollably, especially in OLTP or time-series workloads. As millions or billions of rows accumulate, you begin to notice:Slow queries due to full table scans or massive indexes.Heavy I/O usage, especially when indexes cannot fit in memory.Bloated memory during operations like sorting or joining.Increased maintenance cost, with longer VACUUM, ANALYZE, and REINDEX times.Hard-to-manage retention policies, as purging old rows becomes expensive.These problems are amplified in cloud-hosted databases, where every IOPS, GB, or CPU upgrade increases cost.
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Finding Bottlenecks and Avoiding Over-Optimization via Explain Plans

Performance optimization in a production database is important, but trying to over-optimize can make things more complicated without real improvements.In this post, I’ll share two very basic EXPLAIN ANALYZE outputs from a production system. A user asked us to help optimize these queries. I've changed the table and column names for privacy. We will look at how to spot slow parts of a query, improve performance the right way, and avoid unnecessary tuning.Plan A: Identifying and Resolving a BottleneckExecution Plan A (Before Optimization) Nested Loop (cost=1000.42..25607.38 rows=1 width=129) (actual time=78.521..90.445 rows=0 loops=1) -> Gather (cost=1000.00..25598.95 rows=1 width=65) (actual time=78.520..90.443 rows=0 loops=1) Workers Planned: 2 Workers Launched: 2 -> Parallel Seq Scan on <table_1> e (cost=0.00..24598.85 rows=1 width=65) (actual time=75.351..75.351 rows=0 loops=3) Filter: ((<column_1>) = '<date_value>'::date) AND ((<column_2>)::text = '<event_type>'::text) Rows Removed by Filter: <number_removed_rows> -> Index Scan using <index_name> on <table_2> a (cost=0.42..8.43 rows=1 width=41) (never executed) Index Cond: ((<column_3>)::text = (<column_4>)::text) Filter: ((<column_5>)::text = '<default_value>'::text) Planning Time: 0.466 ms Execution Time: 90.580 ms
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SELECT FOR UPDATE – Reduce Contention and Avoid Deadlocks to Improve Performance in PostgreSQL

Relational databases are at the heart of countless applications around the world, from high-traffic e-commerce websites to enterprise resource planning (ERP) systems and financial services. Concurrency management—where multiple database transactions operate on the same data simultaneously—is critical to getting good performance and avoiding problems like deadlocks or data inconsistencies.When multiple transactions need to modify the same rows, ensuring data consistency can become tricky. A single wrong approach to locking can lead to suboptimal performance or even bring your application to a standstill as numerous transactions block one another. One tool in PostgreSQL’s arsenal to handle concurrency is SELECT FOR UPDATE. It allows you to lock specific rows before updating them, preventing other transactions from modifying those rows until your transaction completes.In this blog, we will dive deep into SELECT FOR UPDATE in PostgreSQL. We will explore how it helps in reducing contention, avoiding deadlocks, and ultimately boosting performance when dealing with highly concurrent applications.
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When HASH partitioning works better than RANGE in PostgreSQL

When HASH partitioning works better than RANGE

I have always been a fan of RANGE partitioning using a date/time value in PostgreSQL. This isn't always possible, however, and I recently came across a scenario where a table had grown large enough that it had to be partitioned, and the only reasonable key to use was a UUID styled identifier.The goal of this post is to highlight when and why hashing your data across partitions in PostgreSQL might be a better approach.Range vs. Hash Partitioning in PostgreSQLRange Partitioning (A Quick Recap)Range partitioning in PostgreSQL uses boundary values that define slices of the data, often by date or numeric ranges. If you have a transactions table, you might create monthly partitions based on a transaction_date column. This is intuitive for time-series data because each partition holds rows from a specific date range.Advantages of Range Partitioning:Easy pruning for date-based queries. Straightforward approach to archiving old data: drop an entire partition for a past month, rather than issuing a massive DELETE. Pairs nicely with time-based ingestion pipelines, where every day or month gets its own partition. But as convenient as that is, there are cases where range partitioning runs into problems.Why Range Partitioning Can Fall ShortData Skew: If a huge portion of data lands in a single time interval—say, because of a traffic spike in the current month—that monthly partition might end up significantly larger than the others. Complex Backfills: Not everyone ingests data in an orderly, daily manner. Sometimes you need to re-ingest or correct data that spans multiple periods. Merging or splitting range partitions can get cumbersome. Non-Date Dimensions: Some tables aren’t naturally tied to a sequential numeric or date dimension. If your queries center on user IDs or device IDs, dividing by date might not solve your performance issues.
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