


How to Handle Missing Rows in PostgreSQL UPSERTs with Concurrent Transactions?
Handling missing result rows in PostgreSQL UPSERT operation
In PostgreSQL 9.5, using RETURNING
and ON CONFLICT
together sometimes resulted in missing rows when concurrent transactions updated specified conflicting targets.
Disadvantages of the currently accepted answer
The currently accepted answer is prone to problems when concurrent transactions update multiple rows in the target table. While it prevents missing rows, it introduces other side effects and performance penalties associated with empty updates.
Alternatives
No concurrent write load:
WITH input_rows(usr, contact, name) AS ( VALUES (text 'foo1', text 'bar1', text 'bob1') -- 第一行中的类型转换 , ('foo2', 'bar2', 'bob2') -- 更多? ) , ins AS ( INSERT INTO chats (usr, contact, name) SELECT * FROM input_rows ON CONFLICT (usr, contact) DO NOTHING RETURNING id --, usr, contact -- 返回更多列? ) SELECT 'i' AS source -- 'i' 代表'插入' , id --, usr, contact -- 返回更多列? FROM ins UNION ALL SELECT 's' AS source -- 's' 代表'选择' , c.id --, usr, contact -- 返回更多列? FROM input_rows JOIN chats c USING (usr, contact); -- 唯一索引的列
Having concurrent write load
To resolve race conditions for multiple concurrent transactions:
WITH input_rows(usr, contact, name) AS ( ... ) -- 如上所示 , ins AS ( INSERT INTO chats AS c (usr, contact, name) SELECT * FROM input_rows ON CONFLICT (usr, contact) DO NOTHING RETURNING id, usr, contact -- 我们需要唯一的列来进行后续连接 ) , sel AS ( SELECT 'i'::"char" AS source -- 'i' 代表'插入' , id, usr, contact FROM ins UNION ALL SELECT 's'::"char" AS source -- 's' 代表'选择' , c.id, usr, contact FROM input_rows JOIN chats c USING (usr, contact) ) , ups AS ( -- 罕见的极端情况 INSERT INTO chats AS c (usr, contact, name) -- 另一个UPSERT,不仅仅是UPDATE SELECT i.* FROM input_rows i LEFT JOIN sel s USING (usr, contact) -- 唯一索引的列 WHERE s.usr IS NULL -- 缺失! ON CONFLICT (usr, contact) DO UPDATE -- 我们第一次已经礼貌地请求了…… SET name = c.name -- ……这次我们用旧值覆盖 RETURNING 'u'::"char" AS source -- 'u' 代表更新 , id --, usr, contact -- 返回更多列? ) SELECT source, id FROM sel UNION ALL TABLE ups;
Key points:
-
sel
CTE returns inserted rows and selected rows, providing the complete output result set. -
ups
CTE handles missing rows, updating them with existing values. - The output result set excludes any rows updated by concurrent transactions unless they are
ups
processed.
The above is the detailed content of How to Handle Missing Rows in PostgreSQL UPSERTs with Concurrent Transactions?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics











Full table scanning may be faster in MySQL than using indexes. Specific cases include: 1) the data volume is small; 2) when the query returns a large amount of data; 3) when the index column is not highly selective; 4) when the complex query. By analyzing query plans, optimizing indexes, avoiding over-index and regularly maintaining tables, you can make the best choices in practical applications.

MySQL is an open source relational database management system. 1) Create database and tables: Use the CREATEDATABASE and CREATETABLE commands. 2) Basic operations: INSERT, UPDATE, DELETE and SELECT. 3) Advanced operations: JOIN, subquery and transaction processing. 4) Debugging skills: Check syntax, data type and permissions. 5) Optimization suggestions: Use indexes, avoid SELECT* and use transactions.

MySQL is suitable for beginners because it is simple to install, powerful and easy to manage data. 1. Simple installation and configuration, suitable for a variety of operating systems. 2. Support basic operations such as creating databases and tables, inserting, querying, updating and deleting data. 3. Provide advanced functions such as JOIN operations and subqueries. 4. Performance can be improved through indexing, query optimization and table partitioning. 5. Support backup, recovery and security measures to ensure data security and consistency.

The main role of MySQL in web applications is to store and manage data. 1.MySQL efficiently processes user information, product catalogs, transaction records and other data. 2. Through SQL query, developers can extract information from the database to generate dynamic content. 3.MySQL works based on the client-server model to ensure acceptable query speed.

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.
