{"id":111407,"date":"2026-08-07T12:00:00","date_gmt":"2026-08-07T12:00:00","guid":{"rendered":"https:\/\/www.red-gate.com\/simple-talk\/?p=111407"},"modified":"2026-07-14T12:39:01","modified_gmt":"2026-07-14T12:39:01","slug":"how-to-ensure-replication-stability-in-postgresql-fix-prevent-lag-bloat-and-bottlenecks","status":"publish","type":"post","link":"https:\/\/www.red-gate.com\/simple-talk\/databases\/postgresql\/how-to-ensure-replication-stability-in-postgresql-fix-prevent-lag-bloat-and-bottlenecks\/","title":{"rendered":"How to ensure replication stability in PostgreSQL (fix\/prevent lag, bloat, and bottlenecks)"},"content":{"rendered":"\n<p><strong>PostgreSQL replication is one of the most powerful tools available for keeping your database resilient, redundant, and performant, but it&#8217;s only effective when it&#8217;s stable. Replication lag, network bottlenecks, and long-running transactions can each quietly erode the reliability your applications depend on. <\/strong><\/p>\n\n\n\n<p><strong>This guide breaks down how replication works in PostgreSQL, what threatens its stability, and the practical steps you can take to keep everything running smoothly &#8211; from tuning <code>postgresql.conf<\/code>, to handling table bloat and DDL changes safely on large, active databases.<\/strong><\/p>\n\n\n\n<p>If you\u2019re an avid user of any database management system (DBMS), you likely know about <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/sql-server\/database-administration-sql-server\/how-to-set-up-transactional-replication\/\" target=\"_blank\" rel=\"noreferrer noopener\">replication<\/a> within them &#8211; or at least, the basics for your system of choice. Replication isn\u2019t a silver bullet &#8211; each DBMS does it differently &#8211; and this article is focused on replication in <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/postgresql\/\" target=\"_blank\" rel=\"noreferrer noopener\">PostgreSQL<\/a>. More specifically, how to ensure replication stability in PostgreSQL.<\/p>\n\n\n\n<p>It&#8217;s important to first understand the basics: what is replication, and how does it work in PostgreSQL?<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-how-does-replication-work-in-postgresql\">How does replication work in PostgreSQL?<\/h2>\n\n\n\n<p>Replication in PostgreSQL is the process of keeping one PostgreSQL-based database server in sync with another. And, just like in other DBMS&#8217; like <a href=\"https:\/\/www.red-gate.com\/simple-talk\/blogs\/beginners-guide-to-mysql-replication-part-1\/\" target=\"_blank\" rel=\"noreferrer noopener\">MySQL<\/a>, replication in PostgreSQL has elements unique to itself. <\/p>\n\n\n\n<p>For example, if you run two database servers and replicate data, any changes to the data on the primary server are recorded in a <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/sql-server\/database-administration-sql-server\/questions-about-sql-server-transaction-log-you-were-too-shy-to-ask\/\" target=\"_blank\" rel=\"noreferrer noopener\">transaction log<\/a> &#8211; also known as a <a href=\"https:\/\/www.sqlservercentral.com\/editorials\/what-write-ahead-logging-is-and-why-it-matters\" target=\"_blank\" rel=\"noreferrer noopener\">write-ahead log (WAL)<\/a>.<\/p>\n\n\n\n<p>Further, PostgreSQL has several replication types available. The most popular are streaming (physical) replication, logical replication, and WAL file shipping, as explained below.<\/p>\n\n\n<div class=\"block-core-list\">\n<ul class=\"wp-block-list\">\n<li><strong>Physical replication<\/strong> aims to copy your entire database by acting on write-ahead log (WAL) records.<br><br><\/li>\n\n\n\n<li><strong>Logical replication<\/strong> aims to replicate changes to data (anything that\u2019s affected by CRUD SQL queries) rather than act on WAL records.<br><br><\/li>\n\n\n\n<li><strong>WAL file shipping<\/strong> is an older EDB replication technique aiming to copy archived WAL files from one server to another. This PostgreSQL replication technique is simple but quite outdated.<\/li>\n<\/ul>\n<\/div>\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"487\" height=\"608\" src=\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2026\/06\/image-5.png\" alt=\"A basic illustration of streaming replication in PostgreSQL.\" class=\"wp-image-111408\" srcset=\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2026\/06\/image-5.png 487w, https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2026\/06\/image-5-240x300.png 240w\" sizes=\"auto, (max-width: 487px) 100vw, 487px\" \/><figcaption class=\"wp-element-caption\"><em>A basic illustration of streaming replication in PostgreSQL<\/em><\/figcaption><\/figure>\n\n\n\n<p>Above is a basic illustration of streaming (or &#8216;standby&#8217;) replication in PostgreSQL, where secondary read-only database servers continuously copy data from the primary database server. Such a replication method is used to ensure <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/theory-and-design\/department-of-redundancy-department\/\" target=\"_blank\" rel=\"noreferrer noopener\">data redundancy<\/a>, allows developers to offload read-based queries, and acts as a backup should the primary server go AWOL.<\/p>\n\n\n\n<p>Essentially, since WAL records in the standby server are constantly fetched and updated to mirror the state of the primary server, if something happens to the main server powering your application, the secondary server will step up and take over.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-how-to-achieve-data-stability-with-replication\">How to achieve data stability with replication<\/h2>\n\n\n\n<p>Just as there are many methods to replicate data, there are multiple goals replication helps us achieve, and data stability is one of them. To keep data stable, replication needs to be stable as well. For many developers, replication is only as good as the stability it provides.<\/p>\n\n\n\n<p>Since replication is the cornerstone of so many business-critical applications, it relies heavily on limited to continuous communication between the primary and replica servers, up-to-date hardware, and stable workloads (to name a few). <\/p>\n\n\n\n<p>If they\u2019re not up to par, the risk of problems like <a href=\"https:\/\/www.geeksforgeeks.org\/system-design\/replication-lag-in-distributed-systems\/\" target=\"_blank\" rel=\"noreferrer noopener\">replication lag<\/a>, consumption of disk space, and <a href=\"https:\/\/www.postgresql.org\/docs\/current\/warm-standby-failover.html\" target=\"_blank\" rel=\"noreferrer noopener\">improper failover mechanisms<\/a> increases substantially. Let&#8217;s take a closer look at these.<\/p>\n\n\n\n<section id=\"my-first-block-block_1eb266d4d15dde03028c9ffb76d8d470\" class=\"my-first-block alignwide\">\n    <div class=\"bg-brand-600 text-base-white py-5xl px-4xl rounded-sm bg-gradient-to-r from-brand-600 to-brand-500 red\">\n        <div class=\"gap-4xl items-start md:items-center flex flex-col md:flex-row justify-between\">\n            <div class=\"flex-1 col-span-10 lg:col-span-7\">\n                <h3 class=\"mt-0 font-display mb-2 text-display-sm\">Get started with PostgreSQL &#8211; free book download<\/h3>\n                <div class=\"child:last-of-type:mb-0\">\n                                            &#8216;Introduction to PostgreSQL for the data professional&#8217;, written by Grant Fritchey and Ryan Booz, covers all the basics of how to get started with PostgreSQL.                                    <\/div>\n            <\/div>\n                                            <a href=\"https:\/\/www.red-gate.com\/hub\/books\/introduction-to-postgresql-for-the-data-professional\/\" class=\"btn btn--secondary btn--lg\" aria-label=\"Download your free copy: Get started with PostgreSQL - free book download\">Download your free copy<\/a>\n                    <\/div>\n    <\/div>\n<\/section>\n\n\n<h2 class=\"wp-block-heading\" id=\"h-what-hinders-replication-stability-in-postgresql\">What hinders replication stability in PostgreSQL?<\/h2>\n\n\n\n<p>In PostgreSQL, replication stability can be negatively impacted by replication lag, network bottlenecks, and VACUUM-based bottlenecks. Let&#8217;s have a look at each in more detail.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-replication-lag\">Replication lag<\/h3>\n\n\n\n<p><strong>What<\/strong> <strong>is replication lag?<\/strong><br>Replication lag is the delay that occurs when data changes in one part of a database or application take time to be displayed in other parts.<\/p>\n\n\n\n<p><strong>How do you fix\/prevent replication lag?<\/strong><br>Balance the infrastructure behind your database, tune your database to make good use of the infrastructure that you <em>do<\/em> have, and use application-level <a href=\"https:\/\/www.cisco.com\/site\/us\/en\/learn\/topics\/networking\/what-is-routing.html\" target=\"_blank\" rel=\"noreferrer noopener\">routing<\/a> to avoid overwhelming your database.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-network-bottlenecks\">Network bottlenecks<\/h3>\n\n\n\n<p><strong>What are network bottlenecks?<\/strong><br>Network bottlenecks happen when the amount of data being replicated exceeds the capacity of the network. This creates a &#8216;choke point&#8217; and causes data to &#8216;drop&#8217; (or lag behind), resulting in further issues.<\/p>\n\n\n\n<p><strong>How do you fix\/prevent network bottlenecks?<\/strong><br>Use proper hardware, remove bandwidth limits on your network (if any), reduce data sent in transit (compress if possible), and optimize tasks related to your network.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-vacuum-based-bottlenecks\">VACUUM-based bottlenecks<\/h3>\n\n\n\n<p><strong>What are VACUUM-based bottlenecks?<\/strong><br>These occur when cleanup operations performed by the <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/postgresql\/learning-postgresql-with-grant-introducing-vacuum\/\" target=\"_blank\" rel=\"noreferrer noopener\">VACUUM<\/a> maintenance operation in PostgreSQL stall, lag, or otherwise overwhelm your database.<\/p>\n\n\n\n<p><strong>How do you fix\/prevent VACUUM-based bottlenecks?<\/strong><br>Tweak the <code>postgresql.conf<\/code> file: look into delay thresholds (<code>max_standby_archive_delay<\/code> and <code>max_standby_streaming_delay<\/code>) to control how long replicas wait before canceling conflicting <code>SELECT<\/code> queries.<br><br>Also, defer cleanup operations using <code>vacuum_defer_cleanup_age<\/code> to specify cleanup only after a specified number of transactions have completed, scale the replica server by upgrading its hardware or splitting load, and <a href=\"https:\/\/techcommunity.microsoft.com\/blog\/adforpostgresql\/debugging-postgres-autovacuum-problems-13-tips\/3582930\" target=\"_blank\" rel=\"noreferrer noopener\">consider configuring parameters on the primary server to act on disk I\/O where necessary.<\/a><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-what-else-is-a-challenge-for-developers\">What else is a challenge for developers?<\/h2>\n\n\n\n<p>Of course, replication isn\u2019t the only issue developers need to think about in today&#8217;s world. Applying <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/theory-and-design\/data-control-language-aka-security\/\" target=\"_blank\" rel=\"noreferrer noopener\">DDL<\/a> changes safely on large, highly active databases without disrupting production traffic may be problematic, and too many concurrent connections may exhaust server resources. Additionally,  transactions waiting on locks may cause slow queries and reduced throughput.<\/p>\n\n\n\n<p>Developers are also challenged by <a href=\"https:\/\/kendralittle.com\/2025\/12\/01\/index-bloat-postgres-why-it-matters-how-to-identify-and-resolve\/\" target=\"_blank\" rel=\"noreferrer noopener\">table and index bloat<\/a>, <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/sql-server\/long-running-query-detection-in-sql-server\/\" target=\"_blank\" rel=\"noreferrer noopener\">long-running transactions<\/a>, inefficient query plans, and maintaining bigger datasets. <\/p>\n\n\n\n<p>As such, replication stability may not <em>only<\/em> be hindered by replication lag and bottlenecks, but also the other things you do that have an impact on your database as a whole. Some of these include:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-table-and-index-bloat\">Table and index bloat<\/h3>\n\n\n\n<p>Bloat is a byproduct of how PostgreSQL handles operations like <code>UPDATES<\/code> and <code>DELETES<\/code> using <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/postgresql\/multi-version-concurrency-control-mvcc-in-postgresql-learning-postgresql-with-grant\/\" target=\"_blank\" rel=\"noreferrer noopener\">multi-version concurrency control (MVCC)<\/a>, because deleted or updated rows are <em>not<\/em> deleted. Instead, they\u2018re only <em>marked<\/em> as &#8216;deleted&#8217; or &#8216;updated&#8217; in table or index pages.<\/p>\n\n\n\n<p>Use extensions like <a href=\"https:\/\/www.postgresql.org\/docs\/current\/pgstattuple.html\" target=\"_blank\" rel=\"noreferrer noopener\">pgstattuple<\/a> to detect bloat in PostgreSQL. It&#8217;s also beneficial to understand the root causes of bloat: dead tuples, frequent updates to data, and free space fragmentation. These can be avoided through adequate maintenance of your PostgreSQL database.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-long-running-transactions\">Long-running transactions<\/h3>\n\n\n\n<p>Long-running transactions stem from <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/sql-server\/writing-an-efficient-query\/\" target=\"_blank\" rel=\"noreferrer noopener\">poorly-written queries<\/a> or data that is incorrectly optimized for your use case. To keep yourself up to speed on optimizing transactions and the like, <a href=\"https:\/\/www.postgresql.org\/docs\/current\/tutorial-transactions.html\" target=\"_blank\" rel=\"noreferrer noopener\">refer to the official PostgreSQL documentation.<\/a><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-inefficient-query-plans\">Inefficient query plans<\/h3>\n\n\n\n<p>It&#8217;s crucial to understand <em>what<\/em> the query planner chose, and <em>why<\/em>. Give it better information to act on, or better access paths. Start with the basics of <code>ANALYZE<\/code>, <code>EXPLAIN<\/code>, and adding <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/sql-server\/learn\/sql-server-index-basics\/\" target=\"_blank\" rel=\"noreferrer noopener\">indexes<\/a> where applicable. Also look for sequential scans on large tables, huge differences between actual rows and <a href=\"https:\/\/www.red-gate.com\/simple-talk\/blogs\/generating-repeatable-sets-of-test-rows\/\" target=\"_blank\" rel=\"noreferrer noopener\">estimated rows<\/a>, and expensive sort operations. As a general rule, try to prevent anything that accesses more data than it should.<\/p>\n\n\n\n<p>If necessary, rewrite your queries. For example, the <code>SELECT *<\/code> (instead of <code>SELECT<\/code>) column may be doing more harm than it should. And, assess carefully: do you <em>really<\/em> need these <code>JOIN<\/code>s?<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-maintaining-larger-datasets\">Maintaining larger datasets<\/h3>\n\n\n\n<p>Firstly, ensure the tables bearing lots of rows are partitioned and properly indexed. Indexes should also be used by your queries. Also avoid using lots of unnecessary <a href=\"https:\/\/www.postgresql.org\/docs\/current\/datatype.html\" target=\"_blank\" rel=\"noreferrer noopener\">data types<\/a> &#8211; something PostgreSQL is known for &#8211; because, ultimately, your data and use case needs to be specific to actually make good use of them!<\/p>\n\n\n\n<p>Instead, opt for <a href=\"https:\/\/aws.amazon.com\/what-is\/cidr\/\" target=\"_blank\" rel=\"noreferrer noopener\">classless inter-domain routing (cidr)<\/a> when storing IP addresses. You may also have to switch to <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/sql-server\/learn\/when-use-char-varchar-varcharmax\/\">VARCHA<\/a><a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/sql-server\/learn\/when-use-char-varchar-varcharmax\/\" target=\"_blank\" rel=\"noreferrer noopener\">R<\/a> when migrating because no such data type exists in other systems.<\/p>\n\n\n\n<p>Keep your primary use case in mind. If you\u2018re running a search engine, for example, it\u2018s wise to index columns after the <code>WHERE<\/code> clause. And even if you\u2018ve done that, keep in mind that other query types will slow down. <\/p>\n\n\n\n<p>Finally, monitor and tune <a href=\"https:\/\/www.red-gate.com\/simple-talk\/databases\/postgresql\/uncovering-the-mysteries-of-postgresql-auto-vacuum\/\" target=\"_blank\" rel=\"noreferrer noopener\">autovacuum<\/a>, since many large installations require more aggressive autovacuum settings than the defaults.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-safely-applying-ddl-changes-on-big-data\">Safely applying DDL changes on big data<\/h3>\n\n\n\n<p>Even if your operation is fast, understand that PostgreSQL may briefly lock access to <a href=\"https:\/\/retool.com\/blog\/crud-operations-sql\" target=\"_blank\" rel=\"noreferrer noopener\">CRUD queries<\/a>. Keep in mind that on older versions of PostgreSQL, <em>some<\/em> <code>ALTER TABLE<\/code> statements will trigger a table rewrite, but others won&#8217;t. <code>ADD COLUMN<\/code> may be safe \u2013 add <code>NOT NULL DEFAULT \u2018Value\u2019<\/code> and you may trigger a rewrite. <\/p>\n\n\n\n<p>Consider performing operations (e.g. adding columns to tables) gradually: add a column, backfill existing rows gradually, then add an index if necessary. <\/p>\n\n\n\n<p>Finally, employ <code>CREATE|DROP INDEX CONCURRENTLY<\/code> instead of building or removing indexes in a vanilla way, and backfill lots of data in batches using the <code><a href=\"https:\/\/www.geeksforgeeks.org\/sql\/sql-limit-clause\/\" target=\"_blank\" rel=\"noreferrer noopener\">LIMIT<\/a><\/code> clause where necessary.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-transactions-waiting-on-locks\">Transactions waiting on locks<\/h3>\n\n\n\n<p>Identify waiting\/blocking queries. Keep transactions brief, and avoid user activity when they\u2018re running. Act on (update, etc.) data in smaller batches than usual. Set lock timeouts by using <code>SET lock_timeout<\/code>. Finally, use appropriate isolation levels when necessary.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-summary-why-you-should-fix-these-postgresql-issues\">Summary: why you should fix these PostgreSQL issues<\/h2>\n\n\n\n<p>Fix (or better still, <em>prevent<\/em>) these issues, and your PostgreSQL will thank you &#8211; not only when replicating your data, but also in other everyday operations. <\/p>\n\n\n\n<p>Your database is the backbone of the operations behind your application &#8211; so it&#8217;s crucial to know how to efficiently manage table and index bloat, deal with long-running transactions, and maintain large datasets. Not only for the present, but for the future of your database, too.<\/p>\n\n\n\n<section id=\"my-first-block-block_47accc152cfff2647fb755fe04e9bfea\" class=\"my-first-block alignwide\">\n    <div class=\"bg-brand-600 text-base-white py-5xl px-4xl rounded-sm bg-gradient-to-r from-brand-600 to-brand-500 red\">\n        <div class=\"gap-4xl items-start md:items-center flex flex-col md:flex-row justify-between\">\n            <div class=\"flex-1 col-span-10 lg:col-span-7\">\n                <h3 class=\"mt-0 font-display mb-2 text-display-sm\">Simple Talk is brought to you by Redgate Software<\/h3>\n                <div class=\"child:last-of-type:mb-0\">\n                                            Take control of your databases with the trusted Database DevOps solutions provider. Automate with confidence, scale securely, and unlock growth through AI.                                    <\/div>\n            <\/div>\n                                            <a href=\"https:\/\/www.red-gate.com\/solutions\/overview\/\" class=\"btn btn--secondary btn--lg\" aria-label=\"Discover how Redgate can help you: Simple Talk is brought to you by Redgate Software\">Discover how Redgate can help you<\/a>\n                    <\/div>\n    <\/div>\n<\/section>\n\n\n<section id=\"faq\" class=\"faq-block my-5xl\">\n    <h2>FAQs: How to ensure replication stability in PostgreSQL<\/h2>\n\n                        <h3 class=\"mt-4xl\">1. What is replication lag in PostgreSQL and how do you fix it?<\/h3>\n            <div class=\"faq-answer\">\n                <p>Replication lag is the delay between a change being made on the primary server and that change appearing on a replica. It&#8217;s typically caused by insufficient infrastructure, unoptimised queries, or overwhelming write volumes. You can reduce it by balancing your database infrastructure, tuning your configuration, and using application-level routing to distribute load more evenly.<\/p>\n            <\/div>\n                    <h3 class=\"mt-4xl\">2. What are the main types of replication in PostgreSQL?<\/h3>\n            <div class=\"faq-answer\">\n                <p>PostgreSQL supports three primary replication methods: streaming (physical) replication, which copies WAL records continuously to keep replicas in sync; logical replication, which replicates individual data changes from CRUD operations; and WAL file shipping, an older method that copies archived WAL files between servers. Streaming replication is the most widely used in modern setups.<\/p>\n            <\/div>\n                    <h3 class=\"mt-4xl\">3. How does VACUUM affect replication stability in PostgreSQL?<\/h3>\n            <div class=\"faq-answer\">\n                <p>The VACUUM process can stall or overwhelm replicas if it&#8217;s not properly configured, particularly when cleanup operations conflict with active SELECT queries on standby servers. To manage this, adjust <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">max_standby_streaming_delay<\/code> and <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">max_standby_archive_delay<\/code> in <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">postgresql.conf<\/code>, and use <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">vacuum_defer_cleanup_age<\/code> to delay cleanup until a set number of transactions have completed.<\/p>\n            <\/div>\n                    <h3 class=\"mt-4xl\">4. How do you safely apply DDL changes on a large PostgreSQL database without downtime?<\/h3>\n            <div class=\"faq-answer\">\n                <p>Apply changes incrementally: add a column first, then backfill existing rows in batches, then add any required indexes. Use <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">CREATE INDEX CONCURRENTLY<\/code> and <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">DROP INDEX CONCURRENTLY<\/code> to avoid locking tables, and use the <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">LIMIT<\/code> clause when backfilling large datasets. Be aware that some <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">ALTER TABLE<\/code> operations can trigger a full table rewrite on older PostgreSQL versions.<\/p>\n            <\/div>\n                    <h3 class=\"mt-4xl\">5. What causes table bloat in PostgreSQL and how do you prevent it?<\/h3>\n            <div class=\"faq-answer\">\n                <p>Table bloat is a side effect of PostgreSQL&#8217;s multi-version concurrency control (MVCC) system: when rows are updated or deleted, the old versions aren&#8217;t immediately removed &#8211; they&#8217;re marked as dead tuples. Over time, this inflates table and index size. You can detect bloat using the <code class=\"bg-text-200\/5 border border-0.5 border-border-300 text-danger-000 whitespace-pre-wrap rounded-[0.4rem] px-1 py-px text-[0.9rem]\">pgstattuple<\/code> extension and reduce it through regular VACUUM runs, avoiding unnecessary large updates, and tuning autovacuum settings &#8211; especially on high-write or large-table databases.<\/p>\n            <\/div>\n            <\/section>\n","protected":false},"excerpt":{"rendered":"<p>PostgreSQL replication stability depends on more than just configuration. Learn how replication lag, network bottlenecks, and VACUUM-related issues can silently undermine your database, and what to do about each.&hellip;<\/p>\n","protected":false},"author":339547,"featured_media":111423,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[143527,143523,53,143534],"tags":[4168,4170,158978,4150],"coauthors":[146040],"class_list":["post-111407","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-database-administration-sql-server","category-databases","category-featured","category-postgresql","tag-database","tag-database-administration","tag-postgresql","tag-sql"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/posts\/111407","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/users\/339547"}],"replies":[{"embeddable":true,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/comments?post=111407"}],"version-history":[{"count":6,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/posts\/111407\/revisions"}],"predecessor-version":[{"id":111712,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/posts\/111407\/revisions\/111712"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/media\/111423"}],"wp:attachment":[{"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/media?parent=111407"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/categories?post=111407"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/tags?post=111407"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.red-gate.com\/simple-talk\/wp-json\/wp\/v2\/coauthors?post=111407"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}