标签：#SQL

PostgreSQL Error 22036: non numeric sql json item PostgreSQL error code 22036 ( non numeric sql json item ) occurs when a SQL/JSON path expression attempts to perform a numeric operation on a JSON item that is not a number — such as a string, boolean, array, or object. This error was introduced alongside the SQL/JSON Path feature in PostgreSQL 12 and typically surfaces in queries using jsonb_path_query , jsonb_path_exists , or the @@ and @? operators. Top 3 Causes 1. Numeric Values Stored as Strings The most common cause is JSON data where numbers are stored as quoted strings (e.g., "price": "100" instead of "price": 100 ). This frequently happens with data from external APIs or legacy systems that don't enforce type consistency. -- Triggers 22036: "price" is a string, not a number SELECT jsonb_path_query ( '{"price": "100"}' , '$.price + 50' ); -- ERROR: non numeric SQL/JSON item -- Fix: Use the .double() conversion method in JSON Path SELECT jsonb_path_query ( '{"price": "100"}' , '$.price.double() + 50' ); -- Result: 150 -- Alternative fix: Cast at the SQL level SELECT ( data ->> 'price' ):: numeric + 50 FROM ( SELECT '{"price": "100"}' :: jsonb AS data ) t ; -- Result: 150 2. Arithmetic Applied Directly to Arrays or Objects Developers sometimes write JSON Path expressions that target an entire array or object instead of individual elements, then attempt arithmetic on the result. -- Triggers 22036: $.scores returns an array, not a number SELECT jsonb_path_query ( '{"scores": [80, 90, 70]}' , '$.scores + 10' ); -- ERROR: non numeric SQL/JSON item -- Fix: Target a specific array index SELECT jsonb_path_query ( '{"scores": [80, 90, 70]}' , '$.scores[0] + 10' ); -- Result: 90 -- Fix: Use wildcard to apply operation to each element SELECT jsonb_path_query ( '{"scores": [80, 90, 70]}' , '$.scores[*] + 10' ); -- Results: 90, 100, 80 -- Fix: Use unnest for aggregation use cases SELECT elem :: numeric + 10 FROM jsonb_array_elements ( '{"scores": [80, 90, 70]}' :: jsonb ->

Lately I keep reaching for SQLite where, before, I'd have reached for Postgres without thinking. It started with small services, then a bigger question: could a multi-tenant SaaS actually run on SQLite? And for AI agents specifically, isn't a local, embedded database the more natural home for their state? Turso is the version of this stack I've found most compelling so far, especially when paired with Cloudflare. I wish D1 would reach embedded-replica parity with Turso, and that AWS offered a managed SQLite-style service the way it offers RDS for Postgres. This isn't a "Postgres is over" argument. I still use Postgres more often than SQLite. And it isn't advice. It's just where my thinking has drifted recently — written down mostly so I can find out where it's wrong. Read it as one person's notes, not a recommendation. Where I've landed for now (and expect to keep revising): SQLite isn't replacing Postgres. For work state , it's increasingly my first reach, not my last. AI agents push this harder: their state is high-churn, local, and mostly private. The answer isn't all-local. It's a local workbench plus a central ledger . Why the old default existed For years, "where does the data live?" had one practical answer: a server, behind an API, in a shared Postgres. A lot of that wasn't architecture — it was the cheapest shape available. SQLite was already everywhere, but it lacked the operational layer that makes a database viable as SaaS infrastructure: networking, replication, managed backups, and a way to run many small databases without drowning in tooling. So centralizing was the path of least resistance, and a tenant_id column in shared Postgres became the reflex. What changed isn't SQLite. It's that the ecosystem grew the missing parts — and for a growing class of workloads, the thing doing the most frequent writing moved onto my own machine. The constraint that's lifting SQLite itself is, by design: Embedded, not networked — a library, nothing listens on a port.

Data privacy regulations such as GDPR, LGPD, and HIPAA demand that organizations know exactly where Personally Identifiable Information (PII) lives inside their databases. Yet in practice, most teams rely on manual inventories, tribal knowledge, or external scanning tools that require data to leave the database engine — a process that itself creates privacy and security risks. This article presents an MVP that takes a different approach: it runs PII detection inside InterSystems IRIS using Embedded Python, analyzing data where it lives and never exporting it to an external process. The result is a lightweight, non-intrusive utility that scans your tables, identifies PII using AI, and produces a structured CSV report — all without data ever leaving the IRIS process. The Problem: PII You Don't Know You Have Organizations today face a painful blind spot. A typical IRIS instance may contain hundreds of tables across dozens of schemas, some holding decades of accumulated data. Columns named ContactInfo , Notes , or Description might silently contain social security numbers, email addresses, or government IDs — sometimes intentionally, sometimes as a side effect of free-text fields that capture whatever users type in. Traditional approaches to PII discovery share a common flaw: they require data extraction. You export samples, send them to an external service, or pipe them through a standalone tool. Every step in that pipeline is an additional attack surface and a potential compliance violation. The principle of data sovereignty — keeping data within its jurisdiction and under controlled access — suggests a better path: bring the analysis to the data, not the data to the analysis. This is not just a technical preference; it is a governance requirement: GDPR (EU) — Article 28 requires that any processing of personal data by a third-party processor be governed by a binding contract covering subject-matter, duration, purpose, data types, and obligations [ Art. 28 GDPR ]. Art

PostgreSQL 19 Beta has been announced, with general availability expected in September, following the project's yearly major-release cadence. This release introduces native SQL Property Graph Queries (SQL/PGQ), concurrent table repacking to reclaim storage without downtime, and a broad set of performance, observability, and administration improvements. By Renato Losio

This week's Java roundup for June 8th, 2026, features news highlighting: the GA release of A2A Java SDK 1.0; an update on Jakarta EE 12; point releases of Micrometer Metrics and Micrometer Tracing; maintenance releases of GraalVM Native Build Tools and OpenXava; the second release candidate of Gradle 9.6; and the first milestone release of Eclipse JNoSQL 1.2. By Michael Redlich

PostgreSQL HA Risks, Replication Internals, & Rapid Branching Today's Highlights Today's highlights include critical insights into Patroni's replication slot management, an architectural deep dive into PostgreSQL's synchronous commit behavior, and a look at achieving sub-second database branching for enhanced developer workflows. When Patroni Silently Deletes Your Replication Slots (Planet PostgreSQL) Source: https://postgr.es/p/9lM This article uncovers a critical operational pitfall when using Patroni, a popular high-availability solution for PostgreSQL, with logical replication. It details how Patroni, under specific failure scenarios or configuration changes, can silently remove replication slots without warning. Replication slots are vital for ensuring that standbys or logical replication consumers do not miss any changes, making their deletion a potentially severe data integrity issue. The author explains the underlying reasons for this behavior, often related to how Patroni manages pg_basebackup or restores, and how it might not re-create logical replication slots automatically. The post provides concrete scenarios where this can occur, such as when a new primary is elected and old slots aren't re-established, or during certain recovery operations. It emphasizes the importance of diligent monitoring of replication slot status and proposes strategies to mitigate the risk of silent deletion, including careful Patroni configuration and robust alerting mechanisms. This insight is crucial for database administrators and developers relying on Patroni for resilient PostgreSQL deployments, highlighting a subtle but dangerous interaction between these two powerful components. Comment: This is a must-read for anyone running Patroni with PostgreSQL, especially if using logical replication. Understanding this specific behavior of Patroni deleting replication slots silently is essential to prevent unexpected data loss or integrity issues in production. Why Postgres Doesn'

Sometimes you genuinely need the set of columns to update to be data, not code. An operator maps configuration fields to database columns, and you want to honor that mapping without redeploying every time it changes. The naive solution — build an UPDATE string from those column names — is also one of the easiest ways to hand-write a SQL injection vulnerability. This is how to get the flexibility without the hole. We'll build it up in three layers: make it work, make it safe, then count the cost. Layer 1: The dynamic update, the wrong way The tempting version concatenates column names into SQL: // DO NOT do this. var sql = $"UPDATE products SET { columnName } = { value } WHERE id = { id } " ; If columnName comes from configuration that an operator can edit, you've just made your schema writable by whoever controls that config. A value of name = 'x'; DROP TABLE products; -- is now your problem. Even "trusted" config is an injection surface the moment it flows into a SQL string. Layer 2: The same feature with EF.Property EF Core's ExecuteUpdateAsync lets you set a property by name without ever building SQL yourself. EF.Property<T> takes the property name as a string, and EF parameterizes the value and validates the property against the model: await db . Products . Where ( p => p . Id == id ) . ExecuteUpdateAsync ( setters => setters . SetProperty ( p => EF . Property < float ?>( p , columnName ), value )); This is already a different security posture: the value is a parameter, not interpolated text, and EF will throw rather than emit SQL if columnName isn't a real mapped property. But "EF will throw" is a runtime backstop, not a policy. We want to reject bad names before they reach the database, fail closed, and control exactly which columns are writable. Layer 3: Reflection as a whitelist The guard is to validate every incoming column name against the entity's actual properties, using reflection, and to keep an explicit blacklist of fields that must never be touched d

Paginated queries with automatic total count calculation. Supports specifying result fields. public < E > LimitResult < List < E >, E > query ( Class < E > cls , LimitSelect limitSelect ) public < E > LimitResult < List < E >, E > query ( Class < E > cls , LimitSelect limitSelect , LimitRange range ) public < E > LimitResult < List < E >, E > query ( Class < E > cls , LimitSelect limitSelect , List resultFields ) public < E > LimitResult < List < E >, E > query ( Class < E > cls , LimitSelect limitSelect , LimitRange range , List resultFields ) Returns: LimitResult — contains getResult() (data list) and getTotal() (total count). Example: // Define pagination query LimitSelect limitSelect = new LimitSelect () { public SelectOrderByStep from ( SelectSelectStep select ) { return select . from ( T ( "user_table" )) . where ( jt . conditions ( "name%" , name , "birthday>=" , beginDate )); } public List < OrderField > orderBy () { return Arrays . asList ( F ( "birthday" ). desc ()); } }; // Mode 1: return all data, no total count LimitResult res1 = jt . query ( User . class , limitSelect ); // Mode 2: return limit rows, no total count LimitResult res2 = jt . query ( User . class , limitSelect , LimitRange . of ( 20 )); // Mode 3: paginate (offset starts at 0), calculate total count LimitResult res3 = jt . query ( User . class , limitSelect , LimitRange . of ( 20 , 0 )); // res3.getResult() returns data, res3.getTotal() returns total count // Mode 4: specify result fields LimitResult res4 = jt . query ( User . class , limitSelect , LimitRange . of ( 20 , 0 ), Arrays . asList ( "id" , "name" )); // LimitRange.all(): return all data, no total count LimitResult res5 = jt . query ( User . class , limitSelect , LimitRange . all ()); // Access results List < User > data = res3 . getResult (); int total = res3 . getTotal (); About the LimitSelect interface: // LimitSelect is a interface: public interface LimitSelect { // Build the FROM clause; the select parameter allows specifyi

MVCC, WAL, vacuum, and replication slots under sustained delete load - and how to delete billions of rows without your database noticing Most "how to delete a lot of rows" articles stop at "batch it and delete children before parents." That advice is correct, it's table stakes, and everyone already knows it. This article is about everything after that - the parts that actually decide whether your cleanup runs quietly in the background for a week or pages you at 3 a.m. with a full disk and a replica that's six hours behind. The thesis: at scale, your DELETE statement is the easy part. The adversaries are the subsystems a delete feeds - MVCC tuple versioning, the write-ahead log, autovacuum, and the replication machinery. Bulk deletion is really an exercise in flow control across those subsystems . Get the SQL right and the systems wrong, and you'll still take production down. We'll assume PostgreSQL (the internals are PG-specific), a live OLTP primary with at least one physical replica and one or more logical/CDC consumers, and a target of hundreds of millions to billions of rows across many related tables. The one paragraph of "basics," so we can move on: delete in dependency order (referencing rows before referenced rows); collect parent keys once; never rely on ON DELETE CASCADE for huge deletes because you can't throttle a cascade. Done. Now the real material. 1. What a DELETE actually costs A delete is not "remove a row." Under MVCC it's "mark a row version dead and write that fact everywhere." For each deleted tuple, PostgreSQL: Sets xmax on the heap tuple to your transaction id. The row is still physically present; it becomes a dead tuple once your transaction commits and no snapshot can still see it. Writes a WAL record for the heap change. If this is the first modification of that page since the last checkpoint, it also writes a full-page image (FPI) - potentially 8 KB of WAL for a single-row change. Touches every index. Index entries aren't removed at delet

PostgreSQL Error 22P01: Floating Point Exception PostgreSQL error code 22P01 is raised when a floating-point operation produces an exceptional result that cannot be represented as a valid number. This typically occurs during division by zero on float types, operations involving NaN (Not a Number), or arithmetic that yields Infinity . It is most commonly encountered in analytics, financial calculations, and data pipelines processing external or sensor data. Top 3 Causes 1. Division by Zero on Float Types Unlike integer division (which raises 22012 ), dividing a float by zero triggers a floating-point exception. This is especially common in ratio and rate calculations where the denominator can become zero at runtime. -- Problematic query SELECT total_sales :: float / total_orders :: float AS avg_order_value FROM daily_stats ; -- Safe fix using NULLIF SELECT date , total_sales :: float / NULLIF ( total_orders , 0 ):: float AS avg_order_value FROM daily_stats ; 2. NaN Values in Arithmetic Operations Data ingested from external systems, CSVs, or APIs may silently introduce NaN values into float columns. Once NaN participates in arithmetic, results become unpredictable and can trigger exceptions downstream. -- Detect NaN values (NaN is the only value not equal to itself) SELECT id , value FROM sensor_readings WHERE value != value ; -- Replace NaN with NULL safely UPDATE sensor_readings SET value = NULL WHERE value != value ; -- Filter NaN in aggregations SELECT device_id , AVG ( value ) FILTER ( WHERE value = value ) AS clean_avg FROM sensor_readings GROUP BY device_id ; 3. Infinity Arithmetic Conflicts Storing 'Infinity'::float or '-Infinity'::float is valid in PostgreSQL, but performing certain operations on them produces mathematically undefined results (e.g., Infinity - Infinity = NaN ), which can cascade into a floating-point exception. -- Check for Infinity values SELECT id , measurement FROM raw_data WHERE measurement IN ( 'Infinity' :: float , '-Infinity' :: float

Dulu, nyari query yang bikin database spike itu bisa makan berhari-hari. Yang nyari capek, yang nge-fix juga capek. Sekarang? Hitungan jam — dan bonusnya, sambil belajar hal baru juga. Ceritanya begini. Kalau kamu pernah kerja di aplikasi yang pakai ORM (Object-Relational Mapping — semacam "penerjemah otomatis" antara code dan database), pasti familiar sama situasi ini: database tiba-tiba lambat, kamu dapet raw query yang jadi biang kerok, tapi di codebase kamu nulis pakai syntax ORM yang bentuknya beda jauh dari SQL mentah itu. Buat yang belum pernah deal sama ORM, bayangin gini: kamu nulis pesan dalam bahasa Indonesia, lalu ada "penerjemah otomatis" yang convert jadi bahasa Jepang sebelum dikirim ke penerima. Suatu hari ada masalah di pesan yang terkirim — tapi kamu cuma bisa lihat versi bahasa Jepang-nya. Nyari bagian mana dari tulisan Indonesia kamu yang bikin terjemahan-nya bermasalah? Itu effort-nya yang bikin pengen balik tidur aja. Sekarang dengan bantuan Kiro, cukup kasih raw query + akses ke codebase, dia otomatis nyari bagian mana di code yang nge-generate query bermasalah itu. Yang dulu butuh berhari-hari, sekarang bisa selesai dalam hitungan jam — dan itu baru tahap investigasi, belum termasuk fixing-nya. Ceritanya Kenapa Bisa Pakai Kiro Akhir-akhir ini lagi aktif pakai Kiro di tempat kerja. Awal tahun lalu kantor dapat credits melalui program Kiro for Startup , jadi ya sekalian dimaksimalkan. Selain buat debug dan explore query di MS SQL Server, kadang pakai Kiro juga buat analisa log AWS CloudWatch — sambil kasih context aplikasi yang running biar analisa-nya lebih akurat dan gak generic. Di tulisan kali ini, saya mau sharing gimana pakai Kiro sebagai partner beberapa minggu terakhir buat improve query performance di aplikasi .NET Core. Kenapa "partner"? Karena Kiro-nya gak boleh langsung akses ke database — jadi wajib melalui perantara saya. Kita discuss, kolaborasi, dan nge-solve bareng. Bukan AI yang dikasih tombol terus disuruh jalan sendiri. Wakt

One thing that confused me when I first started learning ClickHouse was the word FINAL . Because eventually you'll come across both: SELECT * FROM events FINAL ; and: OPTIMIZE TABLE events FINAL ; At first glance, they sound like they should do roughly the same thing. After all, both contain the word FINAL . But they actually solve two completely different problems. One affects query results. The other affects how data is physically stored. Understanding this distinction can save a lot of confusion when working with MergeTree tables. Why This Confusion Happens Most people encounter FINAL while working with engines like: ReplacingMergeTree SummingMergeTree AggregatingMergeTree Sooner or later they notice something like: SELECT * FROM users ; returns duplicate versions of rows. Then they discover: SELECT * FROM users FINAL ; and suddenly the results look correct. Naturally, many people assume: FINAL merges the table. But that's not exactly what is happening. What SELECT FINAL Actually Does When you run: SELECT * FROM users FINAL ; ClickHouse applies merge logic during query execution. Think of it as: "Show me what the table would look like if all relevant merges had already happened." The important part: It only affects the query result. After the query finishes: parts remain unchanged storage remains unchanged nothing is rewritten on disk The merge logic happens temporarily while the query is running. Once the query completes, the table is exactly as it was before. What OPTIMIZE FINAL Actually Does Now let's look at: OPTIMIZE TABLE users FINAL ; This is a completely different operation. Instead of modifying query results, ClickHouse physically merges parts on disk. The operation: rewrites data merges eligible parts removes obsolete versions creates larger merged parts Unlike SELECT FINAL , the effects remain after the command completes. This is a storage operation, not a query operation. The Simplest Way to Remember It Whenever I think about these commands, I use a v

TL;DR Traditional decoupled ETL pipelines (like the "Modern Data Stack") are too brittle and complex to handle the unpredictable, heavily nested data generated by AI and LLM features. Agentic data serving solves this by focusing on dynamic query routing and semantic discovery, letting AI agents discover and query data autonomously using schema-resilient tools and codified business logic. You can build an agentic data stack by pairing S3 storage with DuckDB's native JSON handling and schema-agnostic Parquet reading ( union_by_name=true ), eliminating failure-prone parsing steps. The open Model Context Protocol (MCP) replaces custom, hacky LangChain tools by providing a standard interface for agents to discover schemas and execute queries securely. The open Model Context Protocol (MCP) and DuckDB's embeddable architecture make it practical to connect agents directly to your data with minimal infrastructure overhead and elastic, consumption-based compute. For years, broken ETL jobs powered my pager and my morning coffee. I am a staff engineer, and like many of you, I have spent a ridiculous amount of my career babysitting data pipelines. It is a thankless job that often feels like patching holes in a sinking ship. You are not alone in this. A Forbes survey shows data teams notoriously spend up to 80% of their time just moving and cleaning data instead of doing the interesting work of analysis. And the financial magnitude of this bottleneck is staggering: the ETL market is projected to reach $20.1 billion by 2032 at a 13% CAGR. This proves that massive industry capital is flowing into solving these pipeline bottlenecks, but throwing more money at the same old architecture was not going to save my mornings. This constant firefighting was frustrating, but manageable. Then came the new mandate: build the data backbone for our next-gen AI and LLM-based product features. The unpredictability of the queries and the sheer complexity of the data, nested JSON everywhere, were th

DuckDB Data Inlining, SQLite Fossildelta OOB, Postgres 19 Temporal Data Today's Highlights Today's highlights include DuckDB's innovative data inlining for stream processing in data lakes, offering significant performance gains by eliminating the small files problem. Additionally, a critical out-of-bounds read vulnerability in SQLite's fossildelta extension and a peek into PostgreSQL 19's focus on temporal data capabilities are discussed. Data Inlining in DuckLake: Unlocking Streaming for Data Lakes (DuckDB Blog) Source: https://duckdb.org/2026/04/02/data-inlining-in-ducklake.html The DuckDB team has unveiled DuckLake’s new data inlining feature, designed to revolutionize how streaming data is managed in data lakes by effectively tackling the notorious “small files problem.” This issue, common in scenarios with frequent small updates or continuous ingestion, often leads to performance bottlenecks due to the overhead of managing numerous tiny files. DuckLake's solution involves intelligently storing these small updates directly within the catalog, thereby eliminating the need for physical small files on disk. This architectural innovation significantly improves the practicality of continuous streaming into data lakes, enabling more efficient real-time analytics. By inlining data, DuckDB reduces I/O operations and metadata management complexity, leading to substantial performance gains. A benchmark highlighted in the announcement demonstrates an impressive 926x speed improvement for certain operations, showcasing the feature's potential to transform data lake architectures for workloads requiring high-throughput ingestion and immediate query access without the traditional performance penalties. Comment: This DuckDB feature is a game-changer for data lake architectures, offering a simple yet powerful way to handle streaming data without the performance overhead of countless small files. Post: Out-of-bounds read in deltaGetInt() when input contains no in-buffer terminat

GBase 8a fully supports OLAP window functions, making it a powerful gbase database for analytical workloads. This guide uses real sales scenarios to demonstrate ROW_NUMBER / RANK , moving aggregates, LAG / LEAD for period‑over‑period comparisons, ROLLUP subtotals, and how these functions execute in an MPP environment. Window Function Syntax function_name () OVER ( [ PARTITION BY column ] -- window group [ ORDER BY column ] -- ordering within window [ ROWS | RANGE BETWEEN ... AND ...] -- frame definition ) Unlike GROUP BY , window functions do not collapse rows. Every row remains in the result set while still being able to “see” other rows in the window. Ranking Functions ROW_NUMBER / RANK / DENSE_RANK SELECT dept_id , salesperson , sale_amount , ROW_NUMBER () OVER ( PARTITION BY dept_id ORDER BY sale_amount DESC ) AS row_num , RANK () OVER ( PARTITION BY dept_id ORDER BY sale_amount DESC ) AS rnk , DENSE_RANK () OVER ( PARTITION BY dept_id ORDER BY sale_amount DESC ) AS dense_rnk FROM sales WHERE sale_date >= '2024-01-01' ; Sample output: dept_id salesperson sale_amount row_num rnk dense_rnk 101 Zhang San 95000 1 1 1 101 Li Si 95000 2 1 1 101 Wang Wu 82000 3 3 2 101 Zhao Liu 71000 4 4 3 Top 3 Sales per Department WITH ranked AS ( SELECT dept_id , salesperson , sale_amount , ROW_NUMBER () OVER ( PARTITION BY dept_id ORDER BY sale_amount DESC ) AS rn FROM sales WHERE YEAR ( sale_date ) = 2024 ) SELECT dept_id , salesperson , sale_amount FROM ranked WHERE rn <= 3 ORDER BY dept_id , rn ; NTILE: Bucketing SELECT dept_id , salesperson , sale_amount , NTILE ( 4 ) OVER ( PARTITION BY dept_id ORDER BY sale_amount DESC ) AS quartile FROM sales WHERE YEAR ( sale_date ) = 2024 ; Cumulative and Moving Aggregates Year‑to‑Date SELECT dept_id , sale_month , monthly_amount , SUM ( monthly_amount ) OVER ( PARTITION BY dept_id ORDER BY sale_month ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW ) AS ytd_amount FROM ( SELECT dept_id , DATE_FORMAT ( sale_date , '%Y-%m' ) AS sale_month ,

I inherited a SQL Server database with 2.3 million rows. Queries took 45 seconds. Users were frustrated. Dashboards timed out. Here is exactly what I did. Step 1: Find the slowest queries I used SQL Server's query store to identify the top 10 worst performing queries. Step 2: Check the execution plan Missing index warnings everywhere. Also saw table scans on a 2 million row table. Step 3: Add targeted indexes Created two non-clustered indexes on the most filtered columns. No over-indexing. Just what the queries actually needed. Step 4: Rewrite the worst join One query was joining 6 tables with a cross apply that made no sense. Restructured to inner joins with proper filter ordering. The result 45 seconds down to 8 seconds. An 82% improvement. Real-time dashboards started working again. Key lesson Check what is actually slow before changing anything. Most people skip this and waste time optimizing the wrong thing. What is your fastest query optimization win?

I inherited a SQL Server database with 2.3 million rows. Queries took 45 seconds. Users were frustrated. Dashboards timed out. Here is exactly what I did. Step 1: Find the slowest queries I used SQL Server's query store to identify the top 10 worst performing queries. Step 2: Check the execution plan Missing index warnings everywhere. Also saw table scans on a 2 million row table. Step 3: Add targeted indexes Created two non-clustered indexes on the most filtered columns. No over-indexing. Just what the queries actually needed. Step 4: Rewrite the worst join One query was joining 6 tables with a cross apply that made no sense. Restructured to inner joins with proper filter ordering. The result 45 seconds down to 8 seconds. An 82% improvement. Real-time dashboards started working again. Key lesson Check what is actually slow before changing anything. Most people skip this and waste time optimizing the wrong thing. What is your fastest query optimization win?

Let's consider a table user . When we execute a query to find Emily , we are actually going through each record , looking whether the name column equals Emily . Indexes comes in when you want to speed this up. Let's create an Index with the name idx_users_name (the name can be anything, and it doesn't matter functionally): CREATE INDEX idx_users_name ON users ( name ); Now when you run SELECT * FROM users WHERE name = 'Emily' ; Postgres will use the index we just created (not by the name, the name is just for us) to execute that query, and the time complexity is reduced from O(n) to O(log n) .

Something is slow. Maybe a page takes forever to load, maybe a migration is hanging, maybe your Supabase dashboard just spins. You suspect a query is stuck somewhere in your database, but you can't see what's happening — Postgres doesn't exactly surface this on its own. Turns out it does. You just need to ask. Seeing what's running Postgres keeps track of every active connection and what it's doing in a system view called pg_stat_activity . You can query it like any table: SELECT pid , state , query , age ( clock_timestamp (), query_start ) AS duration FROM pg_stat_activity WHERE state != 'idle' ORDER BY duration DESC ; That gives you every non-idle process — its process ID, current state, the SQL it's running, and how long it's been at it. If something has been running for minutes when it should take milliseconds, you've found your problem. A few things worth knowing about the columns: pid — the process ID, which you'll need if you want to kill it state — usually active (running right now), idle in transaction (sitting inside an open transaction doing nothing), or idle (waiting for work) query — the actual SQL text query_start — when the current query began If you want to include the user and database to narrow things down: SELECT pid , usename , datname , state , query , age ( clock_timestamp (), query_start ) AS duration FROM pg_stat_activity WHERE state != 'idle' ORDER BY duration DESC ; The dangerous one — idle in transaction An active query that's been running for a while is usually just slow. An idle in transaction connection is a different kind of problem — it means someone (or some code) opened a transaction and never committed or rolled it back. The connection is doing nothing, but it's still holding locks, which can block other queries from running. These are the ones that tend to cause cascading slowdowns. If you see one that's been sitting there for longer than expected, it's almost certainly a bug in application code — a missing COMMIT , an unhandled e

PostgreSQL Error 2200G: Most Specific Type Mismatch PostgreSQL error code 2200G ( most_specific_type_mismatch ) is a SQL-standard data exception that occurs when a value's type does not match the most specific (most derived) type expected in a context involving type hierarchies, XML schema types, or user-defined structured types. It most commonly appears when working with composite types, domain hierarchies, or XML processing functions where type inheritance or derivation is in play. While relatively rare in everyday CRUD operations, it can be a significant pain point in enterprise applications with complex type systems. Top 3 Causes and Fixes 1. Composite or Domain Type Hierarchy Mismatch When a function expects a specific domain or composite type but receives a parent/base type, PostgreSQL raises 2200G. Always cast explicitly to the most specific required type. -- Define types CREATE TYPE base_info AS ( name TEXT , value INTEGER ); CREATE DOMAIN specific_info AS base_info ; -- Function expecting the specific domain type CREATE OR REPLACE FUNCTION handle_info ( data specific_info ) RETURNS TEXT AS $$ BEGIN RETURN ( data ). name || ': ' || ( data ). value ; END ; $$ LANGUAGE plpgsql ; -- WRONG: passing base type causes mismatch -- SELECT handle_info(ROW('test', 42)::base_info); -- CORRECT: explicit cast to the most specific type SELECT handle_info ( ROW ( 'test' , 42 ):: specific_info ); 2. XML Type Processing Mismatch Using XML functions like XMLTABLE or XMLCAST without explicitly matching the expected schema type can trigger this error. Always declare column types explicitly. -- Correct: explicitly typed columns in XMLTABLE SELECT * FROM XMLTABLE ( '//product' PASSING XMLPARSE ( DOCUMENT ' <products> <product> <id>1</id> <price>29.99</price> </product> </products> ' ) COLUMNS product_id INTEGER PATH 'id' , price NUMERIC PATH 'price' ); -- Explicit XMLCAST to resolve type ambiguity SELECT XMLCAST ( XMLQUERY ( '//price/text()' PASSING XMLPARSE ( DOCUMENT '<data><pri