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QUERY CACHE Hint
Written by MinJong Kim on 12/09/2021 ABOUT QUERY CACHE With the release of CUBRID 11.0, the CUBRID DBMS supports QUERY CACHE hint. In this article, we will take some time to look at QUERY CACHE. 1. What is Query Cache? Query Cache is a DBMS feature that stores the statements together with the retrieved record set in memory using the SELECT query statement and returns the previously cached values when the identical query statement is requested. The query cache can be useful in an environment where you have tables that do not change very often and for which the server receives many identical queries. Queries using the QUERY_CACHE hint are cached in a dedicated memory area, and the results are also cached in separate disk space. Query Cache Features 1. The QUERY_CACHE hint only applies to SELE... -
Monitoring CUBRID through Scouter
Written by TaeHwan Seo on 01/18/2022 CUBRID users can monitor items in CUBRID through the Scouter. It was developed based on CUBRID 11.0 version. Full features are available from CUBRID 10.2.1 Version. Scouter (Server, Client) is available from version 2.15.0, bug fixes and features will be added by participating in Scouter GitHub in the future. The latest version of Scouter (as in 2022.01.18) is Scouter 2.15.0, Multi Agent support and bug fixes are currently in the PR stage. 1. What is Scouter? Scouter is an Open Source Application Performance Management (APM), it provides monitoring function for applications and OS. Scouter Basic Configuration Scouter-provided Information - WAS Basic Information Response speed/profiling information for each request, number of server requests/number of re... -
CUBRID INTERNAL: CUBRID Double Write Buffer
Written by MyungGyu Kim on 03/08/2022 INTRODUCTION Data in the database is allocated from disk to memory, some data is read and then modified, and some data is newly created and allocated to memory. Such data should eventually be stored on disk to ensure that it is permanently stored. In this article, we will introduce one of the methods of storing data on disk in CUBRID to help you understand the CUBRID database. The current version at the time of writing is CUBRID 11.2. DOUBLE WRITE BUFFER First of all, I would like to give a general description of the definition, purpose, and mechanism of Double Write Buffer. What is Double Write Buffer? By default, CUBRID stores data on disk through Double Write Buffer. Double Write Buffer is a buffer area composed of both memory and disk. By default, t... -
CUBRID DBLink
Written by DooHo Kang on 27/06/2022 What is CUBRID DBLink When retrieving information from a database, it is often necessary to retrieve information from an external database. Therefore, it is necessary to be able to search for information on other databases. CUBRID DBLink allows users to use the information on other databases. CUBRID DBLink provides a function to inquire about information in the databases of homogeneous CUBRID and heterogeneous Oracle and MySQL. * It is possible to set up multiple external databases, but when searching for information, it is possible to inquire about information from only one other database. CUBRID DBLink Configuration CUBRID DBLink supports DBLink between homogeneous and heterogeneous DBLinks. Homogeneous DBLink diagram If you look at the conf... -
CUBRID INSIDE: Subquery and Query Rewriter (View Merging, Subquery Unnest)
Written by SeHun Park on 08/07/2021 What is Subquery A subquery is a query that appears inside another query statement. Subquery enables us to extract the desired data with a single query. For example, if you need to extract information about employees who have salary that is higher than last year’s average salary, you can use the following subquery: It is possible to write a single query as above without writing another query statement to find out the average salary. Subquery like this has various special properties, and their properties vary depending on where they are written. scalar subquery: A subquery in a SELECT clause. Only one piece of data can be viewed. inline view: A subquery in the FROM clause. Multiple data inquiry is possible. subquery: A subquery in the WHERE clause. I...