DEV Community: Mafiree

Tracking PostgreSQL Operations in Real Time: A Complete Guide to Progress Reporting

Mafiree — Mon, 18 May 2026 09:36:27 +0000

The Core Problem: Operating Without Visibility

Anyone managing a PostgreSQL database has faced the same recurring question during a long-running operation: "Is it done yet?" Index creation, vacuuming, bulk data loads, and base backups can run for minutes or hours, and without proper visibility, they behave like black boxes. PostgreSQL progress reporting system solves this by exposing the internal state of these operations through live, queryable system views — no log parsing, no guesswork, no waiting.
In production environments spanning fintech, SaaS, and e-commerce stacks, progress visibility is typically the first tool DBAs reach for during maintenance windows and live migrations.

What Is PostgreSQL Progress Reporting?

Progress reporting in PostgreSQL refers to a collection of dynamic system views that reflect the real-time status of long-running internal operations. These are in-memory, live views — they show what PostgreSQL is doing right now, updated continuously as operations proceed. No additional configuration or logging is required to use them.

Why It Matters: Operational Benefits

Before these views existed, DBAs had limited options: parse logs, use pg_stat_activity for rough signals, or simply wait. This created real uncertainty around maintenance windows, disaster recovery tests, and bulk operations. Progress reporting addresses this across several dimensions:
Bottleneck Detection — Identify exactly which phase of an index build or vacuum is consuming the most time, rather than guessing from logs.
Automation-Ready Metrics — These views are standard SQL-queryable, making them easy to integrate into monitoring scripts, alerting pipelines, and auto-scaling triggers.
Better Planning — Completion percentages derived from fields like blocks_done vs. blocks_total allow teams to schedule follow-up tasks and communicate reliable timelines.
Stuck Operation Detection — When an operation stalls due to lock contention, I/O saturation, or waiting transactions, the phase column makes it immediately visible rather than requiring deep investigation.
Confident Maintenance Windows — Live monitoring of operations like VACUUM and CLUSTER makes it easier to decide whether to let an operation continue or intervene before it overruns a scheduled window.
Reliable ETAs for Stakeholders — Instead of vague estimates, teams can share data-backed completion percentages, which is particularly important when coordinating across teams during migrations or upgrades.
Crucially, these views are lightweight and read from in-memory statistics, so querying them does not meaningfully impact database performance.

The Complete List of Progress Views (PostgreSQL 18)

PostgreSQL provides six dedicated progress-reporting views, each targeting a specific operation:

pg_stat_progress_vacuum — tracks table vacuuming
pg_stat_progress_analyze — tracks table analysis
pg_stat_progress_create_index — monitors index creation
pg_stat_progress_cluster — tracks heap rewrites during clustering
pg_stat_progress_copy — monitors COPY FROM/TO operations
pg_stat_progress_basebackup — tracks base backup progress

1. Monitoring VACUUM: pg_stat_progress_vacuum

When to use it: Query this view whenever autovacuum or a manual VACUUM is running on a large table — especially during post-bulk-load cleanup or when autovacuum appears to be running unusually slowly.
A sample output from the blog shows a VACUUM in the "scanning heap" phase on a table with 73,334 heap blocks total, with scanning just beginning.
Key fields to monitor:

phase — cycles through scanning heap, vacuuming indexes, and cleanup
heap_blks_scanned / heap_blks_total— use these to derive a completion percentage
num_dead_tuples— shows how much bloat is actively being reclaimed
index_vacuum_count — the number of index passes completed so far

2. Monitoring ANALYZE: pg_stat_progress_analyze

When to use it: Most useful when large tables are being analyzed after bulk loads, or when autoanalyze is running longer than expected and you want to understand how far along it is.
A sample output shows an ANALYZE in the "acquiring sample rows" phase, with 517 out of 2,616 sample blocks already scanned.
Key fields to monitor:

phase — either acquiring sample rows or acquiring inherited sample rows
sample_blks_scanned / sample_blks_total — gives sampling completion percentage
ext_stats_computed — tracks progress on multi-column extended statistics
child_tables_done — relevant when analyzing partitioned tables

3. Monitoring Index Builds: pg_stat_progress_create_index

When to use it: Index creation on large tables can take considerable time, especially in CONCURRENTLY mode. This view shows exactly which build phase is underway, making it far easier to estimate completion and diagnose slowdowns.
The blog shows two phases captured in sequence — first the initializing phase (where all block and tuple counts are zero), then the "building index: scanning table" phase where 161 of 2,616 blocks have been processed.
All phases in order:

Initializing
Building index: scanning table
Building index: sorting live tuples
Building index: loading tuples in tree
Index validation: scanning index
Index validation: scanning table
Waiting for old snapshots
Waiting for readers before marking dead

Key fields to monitor:

phase — identifies exactly which build stage is in progress
blocks_done / blocks_total — compute completion percentage during the scan phase
tuples_done / tuples_total — relevant during the sorting phase
partitions_done — useful for CREATE INDEX on partitioned tables
If an index build appears stuck, the phase column reveals whether it is waiting on locks, I/O resources, or other active transactions.

4. Monitoring CLUSTER: pg_stat_progress_cluster

When to use it: The CLUSTER command physically rewrites an entire table in index order — a heavy, locking operation. This view lets DBAs track its progress and plan maintenance windows accordingly, since a CLUSTER that overruns its window can cause significant disruption.
A sample output shows a CLUSTER in the "writing new heap" phase, having scanned all 2,630 heap blocks and written 1,303 tuples so far.
Key fields to monitor:

phase— sequential heap scanning, index scanning heap, or writing new heap
heap_tuples_written / heap_tuples_scanned — row-level rewrite progress
heap_blks_scanned — block-level scan progress
index_rebuild_count — how many indexes have been rebuilt so far during the operation

5. Monitoring COPY Operations: pg_stat_progress_copy

When to use it: COPY is the standard mechanism for bulk data loads and exports. This view is invaluable during ETL jobs and migrations, allowing teams to calculate load speed and estimate when a large import will finish.
A sample output shows a COPY FROM FILE operation with 100,073,472 bytes processed out of 137,777,792 bytes total, with 3,652,000 tuples loaded — working out to approximately 72.6% completion.
Key fields to monitor:

bytes_processed / bytes_total — direct completion percentage (multiply by 100)
tuples_processed — total rows loaded so far
tuples_excluded / tuples_skipped — flags data quality issues mid-load
type — identifies whether the source is FILE, PIPE, PROGRAM, or STDIN, useful for distinguishing load sources

6. Monitoring Base Backups:

pg_stat_progress_basebackup**
When to use it: Base backups can run for a long time on large databases or slow storage. This view tells you exactly which phase the backup is in and how much data has been streamed, removing uncertainty from a critical operational process.
A sample output shows a backup in the "waiting for checkpoint to finish" phase, with no data streamed yet.
All phases in order:

Initializing
Waiting for checkpoint to finish
Estimating backup size
Streaming database files
Waiting for WAL archiving to finish
Transferring WAL files

Key fields to monitor:

phase — a prolonged pause on "waiting for checkpoint to finish" may indicate checkpoint pressure on the server
backup_streamed / backup_total — bytes transferred vs. estimated total (note: backup_total remains NULL until the size estimation phase completes)
tablespaces_streamed — relevant for databases using multiple tablespaces

The Bigger Picture

Taken together, PostgreSQL's progress reporting views transform long-running maintenance operations from opaque, anxiety-inducing processes into transparent, monitorable workflows. DBAs gain precise, phase-level insight into what PostgreSQL is doing at any moment. This enables faster troubleshooting, more confident maintenance planning, accurate stakeholder communication, and more robust monitoring automation — all without any additional configuration or performance cost to the database.

Database Migration Strategies: Zero-Downtime Patterns for MySQL, PostgreSQL & MongoDB

Mafiree — Wed, 13 May 2026 08:03:37 +0000

What Is Database Migration?

Database migration is the process of moving data from one storage system, format, or environment to another — whether shifting from on-premises servers to the cloud or switching database engines entirely. The central challenge is balancing data integrity with application availability. Traditional "Big Bang" approaches can demand hours or even days of downtime, which is unacceptable for modern enterprises that operate around the clock.

The Database Migration Process: Step by Step

A well-structured migration goes far beyond simply moving rows and columns. It begins with Assessment and Planning — auditing both the source and target environments for data volume, schema compatibility (homogeneous vs. heterogeneous), and network latency to ensure the replication traffic can be handled. Next comes Schema Conversion, which for heterogeneous migrations (such as MongoDB to PostgreSQL) involves mapping NoSQL BSON documents to relational SQL schemas using tools like AWS SCT or custom scripts. Finally, Data Cleansing should be done before the move — archiving old records and normalizing data so you're not carrying "junk" into the new environment.

Three Database Migration Strategies

The right strategy depends on your Recovery Time Objective (RTO) and budget. Here's a breakdown of the three most widely used database migration strategies and when to use each.
1. Big Bang Migration — All data is moved in a single operation during a scheduled maintenance window. It's simple to execute and requires no data synchronization, but carries high risk and demands significant downtime. Best suited for small, non-critical databases.
2. Trickle (Phased) Migration — Data is moved incrementally while both old and new systems run in parallel. This lowers risk and enables real-time validation, but is highly complex to manage and requires bi-directional synchronization to prevent data drift. Suitable when short-term parallel systems are tolerable.
3. Zero-Downtime Migration (Live Replication) — The gold standard for enterprise applications. A replica of the production database is set up in the target environment, and Change Data Capture (CDC) keeps both systems in sync until the final cutover. Downtime is effectively zero, rollback is easy, and it's designed for mission-critical workloads that must stay online 24/7.

Zero-Downtime Patterns by Database

MySQL — Primary-Replica Switchover: An initial data dump is taken using mysqldump or Percona XtraBackup, restored to the target, and then Binary Log (Binlog) replication is started to catch up on changes made during the dump. Once replication lag reaches zero, the application is pointed to the new target.
PostgreSQL — Logical Replication: PostgreSQL's logical replication allows migration across different major versions (e.g., PG 12 to PG 16) with near-zero lag. Unlike physical replication, it allows you to sync specific tables, offering greater flexibility during the process.
MongoDB — Replica Set Oplog Tailing: A new node is added to the replica set in the target environment. It syncs data from the primary via the Oplog. For cross-platform migrations (e.g., to MongoDB Atlas), tools like Mongomirror can automate this process.

Common Migration Failures & How to Prevent Them

Even well-planned migrations encounter edge cases. The six most frequent failure patterns are:
Replication Lag Spike — Causes missing rows at cutover. Prevention: set lag threshold alerts below 5 seconds before scheduling cutover.
Schema Mismatch Post-Cutover — Leads to application crashes and NULL constraint errors. Prevention: never skip a schema compatibility audit, especially for heterogeneous migrations.
Silent Data Corruption — Row counts match but checksums differ. Prevention: use MD5/SHA checksum verification on every critical table, not just row counts.
Insufficient Network Bandwidth — Migration takes far longer than planned and replication never catches up. Prevention: benchmark network capacity against data volume before day one.
No Rollback Plan — Failed cutover with no way to revert. Prevention: maintain the source database as a live fallback with a reverse CDC stream until sign-off, with a documented, time-boxed rollback window.
Index Bloat After Cutover — Query performance degrades in the days following go-live. Prevention: run VACUUM/ANALYZE (PostgreSQL) or OPTIMIZE TABLE (MySQL) immediately after cutover.

Testing Strategy: Ensuring Data Integrity

A rigorous testing strategy is what separates a successful migration from a midnight rollback.
Pre-Migration: Verify backups, audit schema compatibility, test network throughput, run at least two full-scale dry runs in a staging environment, and document the rollback plan.
During Migration: Monitor replication lag continuously, watch the CDC error rate, verify lag stays below 5 seconds before cutover, and keep the source database live as a fallback.
Post-Migration: Validate row counts, run MD5/SHA checksum checks, conduct UAT with stakeholders, and follow up with index rebuilds and query plan reviews.

Key Best Practices

Always maintain a verified, off-site backup before starting.
Automate the cutover using DNS TTL adjustments and scripts to minimize the in-between window.
Perform at least two full-scale dry runs in a staging environment that mirrors production.
Monitor for index bloat and cache misses immediately after cutover.
The underlying message is clear: migration failures are largely preventable. The difference between a smooth cutover and a costly outage comes down to preparation, the right tooling, and a disciplined testing strategy executed at every phase of the migration lifecycle.

How Mafiree Cut MongoDB Query Latency by 73% for an E-Commerce Platform

Mafiree — Tue, 05 May 2026 11:28:57 +0000

Background

Mafiree's MongoDB consulting team audited and optimized the query layer of a high-traffic e-commerce platform in India, bringing average API response times down from 340ms to 92ms - a 73% improvement. The work involved diagnosing slow queries, redesigning indexes, restructuring aggregation pipelines, and setting up ongoing monitoring — all without adding a single server.

Why MongoDB Queries Slow Down

MongoDB query optimization challenges typically emerge when datasets outgrow the assumptions made during initial development. Four root causes are identified:
Collection Scans (COLLSCAN): When no matching index exists, MongoDB scans every document in a collection. On a 50-million-document collection, this can take seconds instead of milliseconds.
Inefficient Index Usage: Having indexes isn't enough — the wrong indexes can be just as harmful. A compound index built for one query pattern is useless for a different field combination, even if it looks similar.
Unbounded Aggregation Pipelines: Stages like $lookup and $unwind that run without an early $match force MongoDB to process the entire collection before filtering, turning a 5ms operation into a 5-second one.
Over-Fetching Documents: Returning entire documents when only a few fields are needed wastes network bandwidth, memory, and CPU on deserialization.

The Client's Situation

The client operated a popular e-commerce marketplace built on MongoDB 6.0, running a 3-node replica set on AWS, serving 2 million daily active users, with a product catalog of 12 million documents and an orders collection exceeding 80 million documents.
Performance had degraded gradually over 18 months. Product search API responses averaged 340ms, the checkout flow experienced intermittent timeouts during flash sales, and the analytics dashboard for sellers took over 8 seconds to load. The engineering team had added indexes reactively over time, resulting in 23 indexes on the products collection alone — many redundant or unused.
After optimization, the results were dramatic: product search dropped from 340ms to 92ms, checkout p99 latency fell from 1,200ms to 280ms, the seller dashboard went from 8.2s to 1.8s, collection scans per hour dropped from 4,200 to just 12, active indexes on the products collection were reduced from 23 to 9, and monthly AWS spend fell from $4,800 to $3,200.

The 3-Step Diagnostic Process

Step 1 — Profiler Analysis: The team enabled MongoDB's built-in profiler at level 1 (slow operations only) with a 100ms threshold. Within 24 hours, 14 distinct query shapes responsible for 87% of all slow operations were identified. The top three offenders were the product search query, the order history aggregation, and the inventory availability check.
Step 2 — Explain Plan Analysis: For each slow query, explain("executionStats") was used to examine execution details. The product search query was scanning nearly 4 million documents to return just 20 results. Despite having 23 indexes on the collection, none matched this specific query shape.
Step 3 — Index Usage Audit: Using the $indexStats aggregation, every index was evaluated. 14 of the 23 indexes on the products collection had zero or near-zero usage over the past 30 days. Unused indexes aren't harmless — each one adds overhead to every write operation.

The Four Key Fixes

Fix 1 — ESR Rule for Compound Indexes: MongoDB's ESR (Equality, Sort, Range) rule is the foundation of effective compound index design. Fields used in equality filters come first, followed by sort fields, then range filters. Applying this rule to the product search query brought latency from 340ms to 92ms, and reduced documents examined from 3.8 million to just 847.
Fix 2 — Aggregation Pipeline Refactoring: The seller dashboard pipeline was processing the entire orders collection before filtering. By moving the $match and $sort stages to the beginning, MongoDB could leverage indexes early. Dashboard load time went from 8.2s to 1.8s, and the working document set shrank from 80 million to approximately 45,000 before the expensive $lookup ran.
Fix 3 — Projections and Covered Queries: Several API endpoints were fetching entire 4KB product documents when only a few fields were needed. Adding projections and supporting covering indexes eliminated full document fetches. Listing page API latency reduced by 60% and network bandwidth dropped by 45%.
Fix 4 — Dropping Unused Indexes: After confirming which indexes were safe to remove, 14 unused indexes were dropped. This freed approximately 2.8GB of RAM and noticeably improved write performance. Write latency improved by 18% and monthly AWS spend decreased by $1,600.

Best Practices for Ongoing Performance

The blog concludes with five production best practices: always follow the ESR rule when designing compound indexes; run the slow query profiler continuously rather than only during incidents; audit index usage quarterly using $indexStats and drop what isn't used; always place $match first in aggregation pipelines; and use projections in every query to avoid fetching unnecessary data.
MongoDB query optimization is not something you do once and forget. Data grows, query patterns shift, and application features evolve. The lasting success of this engagement came from the monitoring framework put in place — continuous profiling, automated index audits, and real-time alerting on latency regressions — ensuring performance stays on track as the platform scales.

Change Data Capture (CDC): How It Works, Benefits & Real-World Use Cases

Mafiree — Wed, 29 Apr 2026 07:44:08 +0000

Modern databases are in a constant state of flux. Every second, records are being inserted, modified, and deleted across countless systems. For businesses running platforms like online marketplaces, keeping all connected systems, analytics dashboards, fraud detection engines, and data warehouses in sync with the latest database state is a fundamental challenge. Refreshing entire datasets repeatedly to detect small changes is inefficient and unsustainable. This is the core problem that Change Data Capture (CDC) was designed to solve.

What is Change Data Capture (CDC)?

Change Data Capture is a technique that identifies and tracks modifications made to a database — insertions, updates, and deletions — and propagates only those changes to downstream systems in real time or near real time. Rather than duplicating full datasets on a schedule, CDC zeroes in on exactly what changed. If a customer updates their shipping address, only that single change is captured and forwarded, not the entire customer table. In essence, CDC acts like a live broadcaster for your data, continuously reporting changes the moment they happen.

Why Traditional Approaches Fall Short

Before CDC became mainstream, data systems typically relied on batch processing — large, periodic jobs that copied significant volumes of data between systems at fixed intervals. This introduced multiple drawbacks: slow and delayed updates, heavy system load during transfers, stale analytics, and inefficient use of network and compute resources. As modern applications began demanding real-time responsiveness — instant dashboards, immediate fraud alerts, continuously synchronized services — batch-based approaches could no longer keep up. CDC emerged as the solution by shifting focus from moving entire datasets to tracking only meaningful changes.

How CDC Works

CDC operates much like an activity log. As changes occur in a database, they are recorded chronologically — for example, a profile update at 10:01 AM, a new order at 10:02 AM, an inventory adjustment at 10:03 AM. Instead of repeatedly scanning the full database to identify what changed, CDC reads this change log and streams those events to other systems. The result is fast, targeted data movement without unnecessary duplication, keeping analytics platforms, data pipelines, and downstream applications perpetually up to date.

Key Benefits of Change Data Capture

CDC has become a foundational component of modern data architecture for several important reasons. First, it enables real-time data flow, so downstream systems receive updates almost immediately rather than waiting for scheduled transfers. Second, since only changes are captured rather than full tables, the overall system load is significantly reduced. Third, faster data movement means businesses can analyze and act on information as events unfold rather than hours later. Fourth, multiple systems can stay synchronized with the latest data without requiring constant full replications — a major advantage in distributed, microservices-based environments.

Real-World Use Cases

Many modern digital experiences rely on CDC behind the scenes.

Real-Time Analytics

Companies track customer activity and sales metrics the moment they occur.

Fraud Detection

Financial systems monitor transactions instantly to identify suspicious patterns.

Data Warehousing

Operational databases continuously send updates to analytics platforms.

Microservices Communication

Different services can stay synchronized by reacting to data change events.

Search and Recommendation Systems

Product updates or user activity can immediately trigger updates in recommendation engines or search indexes. CDC helps organizations turn database changes into real-time events that power modern applications.

CDC Across Different Databases

Different databases implement CDC through their own native mechanisms. MySQL uses binary logs (binlogs), which record every database change at the row level. CDC tools tap into these logs to stream changes without repeatedly querying tables. PostgreSQL relies on Write-Ahead Logs (WAL), which capture all committed transactions in order. CDC systems read these logs to replicate changes reliably without impacting the main database workload. MongoDB offers change streams — a built-in feature that lets applications subscribe to real-time document-level updates, making it particularly well-suited for event-driven and microservices architectures. TiDB provides a native CDC tool called TiCDC, purpose-built for distributed environments, which captures changes across nodes and streams them downstream with strong consistency guarantees — ideal for large-scale migrations and real-time processing.

Conclusion

Data is never truly static. Records are constantly being created, changed, and removed across systems. Where older architectures struggled with complex, repetitive batch processes to keep systems aligned, CDC introduces a far more efficient model: capture only what changed, and share it immediately. This shift reduces unnecessary data movement, enables faster application responses, and has made CDC an indispensable building block for real-time analytics, event-driven systems, and modern data pipelines. When you see a dashboard refreshing live or receive an instant application notification, there is a strong likelihood that CDC is quietly working in the background to make it possible.

Key Differences Between MySQL and PostgreSQL Architecture, Performance & Use Cases

Mafiree — Wed, 15 Apr 2026 07:50:54 +0000

When it comes to selecting a database for production environments, the decision goes beyond just popularity. It involves a careful evaluation of architecture, workload requirements, consistency guarantees, and long-term scalability. MySQL and PostgreSQL are the two leading open-source relational databases, and while both use SQL and store data in tables, they are built on fundamentally different philosophies and behave quite differently under real-world conditions. Making the wrong choice can result in performance bottlenecks, scaling difficulties, replication issues, and increased operational complexity.

Difference Between MySQL and PostgreSQL: Core Architecture

Differences Between MySQL and PostgreSQL become clear when you look at their architecture and internal design. MySQL follows a pluggable storage engine architecture, where different engines handle data storage, with InnoDB as the default and most widely used engine. It supports row-level locking, redo/undo logs for crash recovery, and a relatively simpler internal structure. Its core components include an SQL layer with a parser, optimizer, and query cache, operating within a client-server model.
PostgreSQL, in contrast, uses a single, tightly integrated storage engine with a highly extensible core. It is built around true Multi-Version Concurrency Control (MVCC), a process-per-connection model, and deep extensibility that supports custom data types, indexes, and extensions. Its architecture includes an SQL parser and planner, an executor, an MVCC-based storage engine, and background processes like Autovacuum, WAL writer, and Checkpointer. Overall, PostgreSQL stands out for its higher standards compliance and extensibility compared to MySQL.

Performance Comparison: MySQL vs PostgreSQL

For simple, read-heavy workloads such as OLTP and web applications, MySQL is extremely fast and well-optimized. PostgreSQL, while slightly slower for trivial reads, excels in scenarios involving complex joins, subqueries, and analytics thanks to its smarter query planner. For write operations, MySQL delivers faster single-row inserts with less overhead per transaction but can struggle under heavy concurrency. PostgreSQL, with its WAL-based durability model, handles concurrent writes more gracefully and maintains strong transactional consistency.

Concurrency and Locking

MySQL's InnoDB engine uses row-level locks, gap locks, and next-key locking, and in certain scenarios readers can block writers. PostgreSQL implements true MVCC, meaning readers never block writers and writers never block readers. In high-concurrency environments such as banking, payments, and order-processing platforms, PostgreSQL consistently delivers better and more predictable performance.

Replication and High Availability

MySQL offers built-in asynchronous replication, semi-sync replication, Group Replication, and InnoDB Cluster, and is relatively straightforward to configure. PostgreSQL supports both physical streaming replication and native logical replication, and integrates with a rich ecosystem of tools including Patroni, PgBouncer, and HAProxy, enabling near-zero data loss architectures. For logical replication support, PostgreSQL has a clear edge with native capabilities, while MySQL's logical replication remains limited by comparison.

Real-World Use Cases

MySQL is best suited for CMS platforms like WordPress and Joomla, e-commerce websites, read-heavy web applications, and simple SaaS platforms. PostgreSQL is the better choice for financial systems, healthcare platforms, analytics-heavy applications, geospatial workloads using PostGIS, and complex transactional systems.

Security and Ecosystem

PostgreSQL offers advanced role management, row-level security, and better audit extensions, giving it a stronger security and compliance posture. MySQL offers a simpler, basic role-based access model. On the community and ecosystem front, MySQL is backed by Oracle and enjoys massive adoption with broad hosting support. PostgreSQL is community-driven with enterprise-grade extensions and strong open-source governance.

Conclusion

The choice between MySQL and PostgreSQL is not about which is more popular — it is about selecting the architecture that best fits your workload, performance needs, and long-term growth. MySQL works well for simple, read-heavy web applications, while PostgreSQL excels in high-concurrency, complex, and enterprise-grade workloads where consistency and scalability are priorities.

Incremental Backup in PostgreSQL 17: A Practical Guide

Mafiree — Thu, 02 Apr 2026 07:42:24 +0000

Introduction

PostgreSQL 17 introduced native incremental backup support, a major leap forward in database backup strategy. Rather than duplicating the entire dataset every time, incremental backup captures only the data blocks that have changed since the last backup (full or incremental). This drastically reduces backup time, storage consumption, and system overhead. Prior to PostgreSQL 17, achieving this required third-party tools such as pgBackRest or Barman, which added configuration and maintenance overhead. With native support now built into PostgreSQL, the process has become significantly more streamlined.

What Is Incremental Backup?

An incremental backup records only the changes made since the previous backup — whether that was a full backup or an earlier incremental one. Compared to full backups that copy all data regardless of what has changed, incremental backups are leaner, faster, and more storage-efficient.

Key Features in PostgreSQL 17

Native Integration - Incremental backup is now part of PostgreSQL's core, removing the need for external tools for this functionality.
Storage Efficiency - Only modified data pages are backed up, keeping storage usage minimal.
Faster Backups and Recovery - Since less data is processed each time, backup creation is quicker and recovery is streamlined by applying only the required changes on top of the full backup.

How It Works: Step-by-Step

Step 1 - Enable WAL Summarization In the postgresql.conf file, enable the summarize_wal parameter by setting it to on. This activates the WAL summarizer process, which tracks which data blocks have been modified. It can be enabled on either a primary or a standby server. It is set to off by default.
Step 2 - Take a Full Backup Use pg_basebackup to create the initial full backup. This serves as the foundation for all subsequent incremental backups.
Step 3 - Take the First Incremental Backup After inserting or modifying data, run pg_basebackup again with the --incremental flag, pointing to the backup_manifest file from the full backup. This tells PostgreSQL what the baseline was and allows it to capture only the changes since then.
Step 4 - Take Additional Incremental Backups After further data changes, take another incremental backup — this time referencing the backup_manifest from the first incremental backup. Each incremental backup chains to the previous one using its manifest file.

Restoring the Backups

Restoration is handled by pg_combinebackup, a new utility introduced in PostgreSQL 17. It merges the full backup and all incremental backups into a single, usable backup directory. The backups must be provided in chronological order — starting from the full backup, followed by each incremental in sequence. After combining, you adjust the port in the restored directory's postgresql.conf and start the database server using that data directory. Upon verification, all records from the full backup and every incremental backup are present and intact.

What Is pg_combinebackup?

pg_combinebackup is the companion utility that reconstructs a complete, restorable backup from the chain of incremental backups. It automates the merging process and validates the backup chain for consistency, eliminating the need for manual intervention during restoration.

Advantages of Incremental Backup

Cost Savings - Reduced storage usage means lower costs, whether on cloud or on-premises infrastructure.
Improved Performance - Less data transfer reduces system load, making it particularly valuable during peak operational hours.
Scalability - Well-suited for large databases or environments with frequent data changes where full backups would be impractical.

Limitations to Be Aware Of

summarize_wal must be enabled for this feature to work.
Incremental backups only function with pg_basebackup and cannot be taken from a standby server, they must be run on the primary instance.
Restoration depends on a complete, unbroken backup chain. If any backup in the chain is missing, recovery fails.
Backups operate at the cluster level, with no support for per-table backups.
Proper retention of WAL and summary files is required for the feature to function correctly.

Conclusion

Native incremental backup in PostgreSQL 17 addresses two longstanding pain points, storage waste and slow backup windows, while laying a stronger foundation for disaster recovery. The combination of pg_basebackup (with the --incremental flag) and pg_combinebackup makes the entire backup-and-restore workflow cleaner and more efficient, especially for large-scale, high-transaction environments.

ClickHouse Functions You Should Know: A Practical Guide

Mafiree — Tue, 24 Mar 2026 12:22:56 +0000

ClickHouse offers a rich set of built-in functions that make working with large datasets faster and more intuitive. From the addDays() function for date arithmetic to generateUUIDv4() for unique identifier generation, these functions simplify complex queries and optimize storage, making data insights more accessible. This guide walks through the most practical categories.

Array Functions

arrayMap() transforms an array by applying an expression to every element and returning a new array with the results. For example, passing [1, 2, 3] through x -> x+1 produces [2, 3, 4]. It is ideal for in-place data transformation without needing joins or subqueries.
groupArray() collects column values within a group into a single array. It supports an optional max_size parameter to cap array length. This is useful for aggregating a list of players per team or actions per user in chronological order when combined with arraySort.
argMax() / argMin() are aggregate functions that return the value of one column corresponding to the maximum or minimum of another. For instance, querying which product had the highest revenue returns the product name alongside that peak revenue value — making it easy to identify top or bottom performers without complex subqueries.

Window Functions

row_number() assigns a sequential rank to rows within a partition, ordered by a specified column. A practical example is ranking NBA players by salary in descending order — Stephen Curry at rank 1 with $48M, LeBron James at rank 2 with $45M, and so on.
runningDifference() calculates the difference between the current row's value and the previous row's value in a column. This function is particularly useful for analyzing trends over time, such as changes in sales, stock prices, or other numerical data. Note that the first row of each group returns 0, as there is no prior value to compare.

Date and Time Functions

toStartOfYear() resets any date or DateTime value to January 1st at 00:00:00 of the same year. This is handy for grouping and summing data by year, such as calculating total annual sales across multiple years.
addDays(date, n) adds a fixed number of days to a date. A typical use case is computing estimated delivery dates by adding 5 days to an order timestamp.
INTERVAL syntax offers an SQL-standard alternative to addDays(). It uses singular unit keywords — INTERVAL 60 DAY, INTERVAL 2 MONTH, INTERVAL 1 YEAR, etc. — and is especially clean in WHERE clause filters like WHERE order_date >= now() - INTERVAL 60 DAY. Use INTERVAL for static, readable date offsets in WHERE clauses; use addDays() when adding a dynamic number of days from a column value.
timeDiff(dateTime1, dateTime2) returns the difference between two DateTime values in seconds, making it well-suited for measuring event durations or process gaps.

Aggregate Functions

quantile() calculates percentile values across a dataset. The 0.5 quantile represents the 50th percentile (median), while 0.9 and 0.99 represent the 90th and 99th percentiles respectively. This is particularly valuable for web server performance analysis — understanding median, p90, and p99 response times per server.
stddevPop() / stddevSamp() measures data spread. stddevPop computes population standard deviation, while stddevSamp computes sample standard deviation. A low value means data points cluster near the mean; a high value indicates wider variation — useful for detecting inconsistent server latencies.
Aggregate combinators extend standard functions with suffixes. The -If combinator (e.g., sumIf) processes only rows matching a condition. The -Array combinator (e.g., sumArray) processes array elements instead of rows. Both can be combined, but Array must always come before If (e.g., uniqArrayIf).

Full-Text Search

match(string, pattern) performs regular expression matching against string data. It is useful for filtering log messages, validating formats, or extracting patterns — for example, retrieving only log entries that contain the word "Error".

UUID Functions

generateUUIDv4() generates a random version-4 UUID with each call. It is commonly used as a default value for primary key columns to ensure uniqueness across distributed inserts.
generateUUIDv7() (available from ClickHouse v24.1+) produces time-ordered UUIDs based on the UUIDv7 specification. Unlike v4, these UUIDs are chronologically sortable, making them well-suited for primary keys in time-series workloads.

Visual Representation

bar() renders ASCII bar charts directly in query output. It accepts the value, a minimum, a maximum, and a bar width, making it easy to visualize relative server loads or sales figures without needing an external tool.

User Defined Functions (UDFs)

UDFs let users define custom reusable logic using SQL lambda syntax: CREATE FUNCTION name AS (params) -> expression. A simple example is an age-group classifier that returns "Child", "Adult", or "Senior" based on an age value.
**Executable UDFs **go further — they call external scripts (such as Python files) to process data. The configuration is defined in XML files and referenced in config.xml. A practical example shown in the blog masks sensitive data like email addresses and phone numbers, replacing characters while preserving just enough for identification.

Readable Formatting Functions

formatReadableSize() converts raw byte counts into human-readable strings (KB, MB, GB), making storage reports from system.tables far easier to scan.
formatReadableQuantity() formats large numbers into compact representations like thousands, millions, and billions.
formatReadableTimeDelta() converts a seconds value into a descriptive duration — for example, 432,546,534 seconds becomes "13 years, 8 months, 17 days, 7 hours, 48 minutes and 54 seconds."

Recent Version Updates

Notable recent additions include generateUUIDv7() in v24.1+, compound INTERVAL support in v23.8+, arrayFold() in v23.4+ for reducing arrays to a single value, and Variant & Dynamic Types in v24.1+. Date functions like addDays() now consistently support the Date32 type for extended date ranges from 1900 to 2299.Together, these functions cover the breadth of what most data engineers need — from array manipulation and time arithmetic to statistical analysis, unique ID generation, and custom business logic — all within ClickHouse's fast, columnar query engine.
For a detailed understanding of each function with examples and query outputs, refer to our blog Clickhouse Functions

Linux Kernel Live Patching: Zero-Downtime Security Explained

Mafiree — Tue, 17 Mar 2026 09:34:41 +0000

In today’s always-on digital landscape, security teams can’t afford to choose between patching speed and system availability. Linux kernel live patching offers a practical way to close high‑risk vulnerabilities in real time, so infrastructure stays protected while critical services remain fully online.

Security updates can't wait for downtime anymore

Business-critical applications now run 24/7, across global users and time zones, which makes traditional “late-night maintenance windows” harder to schedule and more expensive to execute. Every time security fixes are delayed to avoid downtime, organizations accept unnecessary exposure to known threats.

Conventional kernel patching workflows often force teams into trade-offs: either schedule disruptive reboots, postpone important patches, or coordinate complex, cross-team maintenance plans. Each option carries costs—lost revenue during outages, heightened breach risk from deferred updates, and mounting compliance pressure when vulnerabilities remain open longer than they should.

As Linux becomes the backbone for databases, application servers, and especially SQL Server on Linux deployments, kernel-level security is now a first-order business concern rather than a background IT task. Live patching aligns security remediation with the real-world operating model of always-available systems.

How Linux Kernel Live Patching Solves the Problem

Linux kernel live patching closes the gap between urgent security fixes and the need for uninterrupted uptime by applying targeted updates directly to the running kernel.

This approach delivers clear operational advantages:

Critical kernel vulnerabilities are remediated as soon as patches are available
Servers stay online with no reboot cycles or service restarts
Production databases, applications, and services keep running at full capacity
Maintenance windows shift from “mandatory and urgent” to “optional and planned”
Security teams can align patch deployment with CVE disclosure timelines

Instead of batching patches into periodic maintenance cycles, organizations can move toward a continuous protection model that keeps exposure windows as short as possible.

Where Linux Kernel Live Patching Matters Most

Live patching delivers the greatest value in environments where even brief interruption has direct business or regulatory impact:

Financial services and payment systems where transaction failures immediately affect revenue and customer trust
Healthcare platforms and medical applications that support clinical workflows and patient care
E-commerce and customer-facing web platforms where downtime translates into abandoned carts and lost sales
Telecom and network infrastructure that must sustain large volumes of concurrent connections -** Cloud and SaaS platforms** serving multi-tenant customer bases with strict SLAs
Large-scale enterprise Linux environments that underpin organization-wide operations

In these settings, avoiding both planned and unplanned downtime is essential for protecting revenue, meeting compliance obligations, and maintaining a strong customer experience.

How Mafiree Helps Organizations Stay Secure Without Downtime

Mafiree provides managed Linux kernel live patching and continuous vulnerability remediation engineered for high-availability production environments.

Service capabilities include:

Real-time deployment of critical kernel security patches across fleets
Continuous monitoring for newly disclosed Linux kernel CVEs
Zero-downtime patch management pipelines for production systems
Emergency response processes for high-severity vulnerabilities
Patch status visibility and compliance-ready reporting for audits
Security-focused Linux patching strategy, design, and implementation

By operationalizing live kernel patching, Mafiree helps teams remove the traditional conflict between staying secure and staying online. Contact Mafiree’s Linux experts to implement zero-downtime security in your environment.

The Business Outcome of Linux Kernel Live Patching

When live patching is integrated into standard operations, kernel security becomes a low-friction, continuous safeguard rather than a risky maintenance event.

Organizations typically realize:

Reduced security exposure as critical vulnerabilities are closed quickly instead of waiting for the next maintenance window
Uninterrupted service delivery for customer-facing and internal applications, avoiding revenue and SLA impacts from reboots
Faster compliance alignment by demonstrating timely remediation and continuous security controls
Lower operational overhead through fewer after-hours maintenance windows and less firefighting around delayed patches
Stronger infrastructure resilience as Linux environments stay both up-to-date and highly available

Live kernel patching turns security updates into a background, always-on process that supports long-term operational stability and business continuity.

How Xstreami Simplifies Real-Time MySQL CDC for Businesses

Mafiree — Wed, 04 Mar 2026 04:32:53 +0000

Real-time Change Data Capture (CDC) pipelines built on MySQL are powerful, but the everyday operational challenges of running them safely and efficiently often slow teams down. Xstreami is a platform designed specifically to make MySQL CDC operationally simple and reliable for practical business use-cases—eliminating the burden of custom streaming code, complex deployment workflows, and risky changes.

What Is Xstreami and Why It Matters

Xstreami is a real-time MySQL streaming platform that enables teams to capture changes from MySQL databases continuously and build CDC pipelines without writing and maintaining bespoke streaming code. It listens to CDC events and lets users implement business rules on top of that stream within an integrated platform.
Traditional CDC implementations typically rely on general-purpose streaming tools or extensive codebases that require engineering expertise to configure, deploy, and maintain. In contrast, Xstreami is purpose-built for operational ease, offering a rule-based engine and tools that reduce friction and risk in everyday tasks.

Reducing Operational Complexity

One of the core strengths of Xstreami is how it reduces the operational challenges teams face when building and evolving streaming data pipelines:

Rule-Based CDC Platform:
Instead of embedding business logic inside custom streaming code or external ETL jobs, Xstreami allows teams to define rules (such as joins, validations, and derived fields) directly on the real-time MySQL stream within the platform’s configuration. This eliminates much of the engineering overhead typically associated with CDC transformations.

Preview and Validation Workflows:
Before rules are activated in production, Xstreami enables users to preview or test rules against real live data. This helps catch incorrect logic, data corruption risks, and unintended consequences ahead of time, reducing silent errors in production.

Controlled Replays:
If something goes wrong or rules need to be updated retroactively, Xstreami supports controlled replay of CDC events. This lets teams re-run data through updated rulesets without risking inconsistent state or replicating errors.

Operational Ownership:
Xstreami’s design binds each license to a single source and destination server. This clear one-to-one pairing makes delivery responsibilities explicit and avoids the complexities of managing many downstream consumers from a single stream—something that can introduce coordination challenges in larger CDC ecosystems.

Handling Schema Evolution Safely

Managing schema changes is an important concern for long-running CDC pipelines. When applications evolve, fields may be added or types changed in source MySQL databases. Traditional pipelines often break silently, or require manual schema management.
Xstreami incorporates schema compatibility checks that help ensure changes such as new columns or modified data types do not silently break downstream systems. This allows teams to evolve their source schema comfortably, without compromising the ongoing reliability of their real-time stream.

Use Cases and Broader Applicability

While the blog focuses on operational simplicity, it also highlights that Xstreami is well suited to a variety of real-time analytics and AI workloads where fresh, validated, and enriched data must be delivered continuously with strong operational control and reliability.
This means Xstreami can fit use-cases such as:
Operational Analytics: Feeding real-time tables or dashboards without batching delays.

AI Feature Pipelines: Ensuring feature stores receive up-to-date transactional data.

Event-Driven Architectures: Triggering downstream services based on live database changes.

By providing rule management, previews, controlled replays, and schema safety checks within the CDC platform itself, Xstreami helps data engineering teams build scalable streaming pipelines without reinventing operational controls and tooling each time.

Comparing Xstreami to Generic Streaming Tools

Generic streaming tools (such as raw Kafka setups or open CDC frameworks) offer raw power and flexibility, but still require significant engineering work for day-to-day operations:

Teams typically must write transformation code or customize connectors each time logic changes.
Many infrastructures lack built-in testing or preview capabilities.
Replays and backfills often involve manual operational playbooks.

In contrast, Xstreami positions itself not just as a streaming engine but as an operational platform that brings transformation logic, validation, deployment controls, and reprocessing capabilities under one umbrella—reducing reliance on external tools or custom infrastructure glue.

Conclusion

In summary, Xstreami is designed to make operationalizing real-time MySQL CDC pipelines simpler, safer, and more maintainable for business use cases. By embedding rule logic directly into the CDC platform, offering previews and safe deployment workflows, and supporting controlled replays and schema evolution checks, it enables teams to focus on delivering value from their streaming data instead of wrestling with infrastructure complexity.

MySQL Schema Migration Without Downtime: A Real Fintech Case Study

Mafiree — Thu, 26 Feb 2026 11:17:28 +0000

Making schema changes on very large MySQL tables can easily interrupt production systems if done with standard DDL (Data Definition Language) operations, because those traditionally block reads and writes for the duration of the change. The blog presents a real-world case study of how Mafiree assisted a fintech customer to evolve their MySQL schema on a table holding over 500 million rows without any downtime — ensuring the application remained fully available throughout the migration process.
At a high level, the case study walks through the technical hurdles encountered, the three-phase technical strategy employed, the tools chosen for each phase, key configuration and performance considerations, and best practices that helped the team carry out the migration safely and reliably.
**

Why Zero Downtime Matters and the Challenge

**
When schema changes are applied directly to large MySQL tables, operations like adding columns, modifying indexes, or changing storage parameters typically require rebuilding the table. A full rebuild locks the table, which in high-traffic environments causes service interruptions — reads and writes can be blocked for minutes to hours, depending on size and load. In mission-critical systems, especially in fintech where transaction throughput and uptime are essential, even short interruptions can be unacceptable.
Traditional ALTER TABLE commands without special handling may put heavy locks and pause database operations while the table is rebuilt. This can seriously degrade user experience and disrupt ongoing transactions, particularly with production databases holding hundreds of millions of rows.
**

The Three-Phase Migration Strategy

**
To avoid blocking production traffic, the migration was structured into three distinct phases, each leveraging different tools and MySQL capabilities:
1. Native MySQL 8.0 Online DDL for Simple Changes
The first phase examined whether the desired schema changes were supported natively by MySQL 8.0 using INSTANT or INPLACE DDL operations.
MySQL 8.0 supports several online DDL operations that modify metadata without requiring a full table rebuild, meaning they complete quickly with minimal locking.

For changes that MySQL can handle in place, these operations were applied first because they avoid overhead entirely.

However, some schema changes — particularly those that fundamentally alter row layout or require rebuilding the table — are not supported as online native DDL. For those, external tools were necessary.
2. gh-ost for Large, Complex Alterations
For the more complex schema updates that MySQL native DDL cannot perform without locks, the team used gh-ost (GitHub Online Schema Transmogrifier):
gh-ost works by creating a shadow copy of the target table and incrementally copying data from the original table into the shadow table.

It listens to MySQL’s binary log to capture ongoing changes on the original table and applies these changes to the shadow copy.

Once the shadow copy is fully in sync with active production traffic, gh-ost performs a coordinated swap of table names in a way that incurs only a very brief lock — typically short enough that users do not notice any interruption.

This tool is well suited for extremely large tables where operations need to run without blocking writes or degrading performance drastically.
3. pt-online-schema-change for Compatibility and Specific Cases
In addition to gh-ost, the team also used pt-online-schema-change from the Percona Toolkit:
This tool also creates a shadow table, then mirrors insert/update/delete operations with triggers while copying data in the background.

It works across a broader range of MySQL versions and has strong compatibility with foreign keys, making it useful when certain constraints or environments wouldn’t easily support gh-ost.

By combining gh-ost, pt-online-schema-change, and native DDL, the team could flexibly choose the best approach for each kind of schema change, balancing safety, compatibility, and performance.
**

Performance, Monitoring, and Benchmarks

**
The case study also emphasizes the importance of configuration tuning and observability during a zero-downtime migration:
In the real migration, the 500M-row table transformation with conservative gh-ost throttling (nice-ratio = 0.5) completed in ~4.5 hours.

If the same migration were run with no throttling on dedicated hardware, it could complete in 1.5–2 hours, though aggressive settings are rarely safe in production.

Essential metrics to watch include replication lag across replicas, InnoDB buffer pool hit ratio, disk I/O load, query latency at the p95/p99 percentiles, and job progress outputs from the tools being used.

If any metric shows stress beyond acceptable thresholds, the migration pause mechanisms in gh-ost and pt-online-schema-change can be used to throttle or pause operations, protecting production workloads.

This surveillance and tuning help to maintain a smooth user experience throughout the change.
**

Best Practices and Operational Advice

**
From the case study’s experience, the following practices emerge as key parts of a successful zero-downtime migration:
Choose the Right Tool for the Job: Use MySQL’s native online DDL where possible. Use gh-ost for heavy, binlog-driven copies, and pt-online-schema-change for compatibility with older environments or foreign keys.

Benchmark and Throttle: Run realistic staging tests and use throttling parameters to balance speed against server load.

Monitor Continuously: Keep an eye on replication lag, buffer pools, I/O, and latency. React early if these start trending poorly.

Plan for Rollback: Even with careful planning, be prepared to abort or revert if issues arise that threaten availability or data stability.

Conclusion

**
The Mafiree case study demonstrates that even very large MySQL schema changes can be executed without affecting production uptime, as long as the migration plan is thoughtful and leverages the right mix of native capabilities and specialized tools. By combining MySQL 8.0’s online DDL, gh-ost, and pt-online-schema-change, and by closely monitoring performance and progress indicators, teams can evolve complex database schemas while maintaining seamless service availability.
Ready to unlock MySQL Schema Migration Without Downtime: A Real Fintech Case Study? Dive into the full blog:https://www.mafiree.com/blog/mysql-schema-migration-zero-downtime-case-study