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EmmyMiao87 b3a52a05d5 [Update] Support update syntax (#6230) 
[Update] Support update syntax

    The current update syntax only supports updating the filtered data of a single table.

    Syntax:

     * UPDATE table_reference
     *     SET assignment_list
     *     [WHERE where_condition]
     *
     * value:
     *     {expr}
     *
     * assignment:
     *     col_name = value
     *
     * assignment_list:
     *     assignment [, assignment] ...

    Example
    Update unique_table
         set v1=1
         where k1=1

    New Frontend Config: enable_concurrent_update
    This configuration is used to control whether multi update stmt can be executed concurrently in one table.
    Default value is false which means A table can only have one update task being executed at the same time.
    If users want to update the same table concurrently,
      they need to modify the configuration value to true and restart the master frontend.
    Concurrent updates may cause write conflicts, the result is uncertain, please be careful.

    The main realization principle:
    1. Read the rows that meet the conditions according to the conditions set by where clause.
    2. Modify the result of the row according to the set clause.
    3. Write the modified row back to the table.

    Some restrictions on the use of update syntax.
    1. Only the unique table can be updated
    2. Only the value column of the unique table can be updated
    3. The where clause currently only supports single tables

    Possible risks:
    1. Since the current implementation method is a row update,
         when the same table is updated concurrently, there may be concurrency conflicts which may cause the incorrect result.
    2. Once the conditions of the where clause are unsatisfactory, it is likely to cause a full table scan and affect query performance.
       Please pay attention to whether the column in the where clause can match the index when using it.

    [Docs][Update] Add update document and sql-reference

    Fixed #6229
2021-07-27 13:38:15 +08:00
..
administrator-guide
[Update] Support update syntax (#6230)
2021-07-27 13:38:15 +08:00
best-practices
[Doc] Add a catalog of best practices, and the implementation of Doris FE load balancing (#6231)
2021-07-21 10:51:50 +08:00
community
[Docker] update docker hub url to official repo (#5972)
2021-06-06 22:08:21 +08:00
developer-guide
[Bug] Fix bug that nondeterministic functions should not be rewrote in create view stmt (#6096)
2021-07-13 11:35:35 +08:00
downloads
[Release] Release 0.14 and update 0.14 download url (#5906)
2021-05-26 13:55:40 +08:00
extending-doris
[ODBC] Support ODBC external table of SQLServer and revise the doc. (#6223)
2021-07-21 10:50:56 +08:00
getting-started
[Doc] Avoid ambiguity (#6106)
2021-07-01 09:18:56 +08:00
installing
[BUG][Leak] fix new-delete-type-mismatch in StorageBackend (#6157)
2021-07-08 09:55:22 +08:00
internal
Add flink doris connector design document (#5709)
2021-05-17 11:53:43 +08:00
sql-reference
[Update] Support update syntax (#6230)
2021-07-27 13:38:15 +08:00
README.md
[Doc] correct format errors in English doc (#5321)
2021-02-26 11:32:14 +08:00

README.md

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Welcome to
Apache Doris
A fast MPP database for all modern analytics on big data.
title subTitle descriptions image actionText actionLink
Apache Doris
Apache Doris is a modern MPP analytical database product. It can provide sub-second queries and efficient real-time data analysis. With it's distributed architecture, up to 10PB level datasets will be well supported and easy to operate.
Apache Doris can meet various data analysis demands, including history data reports, real-time data analysis, interactive data analysis, and exploratory data analysis. Make your data analysis easier!
/images/home/structure-fresh.png Learn More /en/getting-started/basic-usage
title subTitle list
Apache Doris Core Features
title icon
Modern MPP architecture /images/home/struct.png
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Getting result of a query within one second /images/home/clock.png
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Support standard SQL language, compatible with MySQL protocol /images/home/sql.png
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Vectorized SQL executor /images/home/program.png
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Effective data model for aggregation /images/home/aggr.png
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Rollup, novel pre-computation mechanism /images/home/rollup.png
title icon
High performance, high availability, high reliability /images/home/cpu.png
title icon
easy for operation, Elastic data warehouse for big data /images/home/dev.png
title subTitle list
Apache Doris Users
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/images/home/logo-meituan.png 美团
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/images/home/logo-xiaomi.png 小米
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/images/home/logo-jd.png 京东
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/images/home/logo-huawei.png 华为
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/images/home/logo-baidu.png 百度
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/images/home/logo-weibo.png 新浪微博
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/images/home/logo-zuoyebang.png 作业帮
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/images/home/logo-vipkid.png Vipkid
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/images/home/logo-360.png 360
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/images/home/logo-shopee.png Shopee
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/images/home/logo-tantan.png 探探
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/images/home/logo-kuaishou.png 快手
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/images/home/logo-sohu.png 搜狐
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/images/home/logo-yidian.png 一点资讯
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/images/home/logo-dingdong.png 叮咚买菜
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/images/home/logo-youdao.png 有道
Quick Start → /en/installing/compilation