Compute
Elastic Cloud Server
Huawei Cloud Flexus
Bare Metal Server
Auto Scaling
Image Management Service
Dedicated Host
FunctionGraph
Cloud Phone Host
Huawei Cloud EulerOS
Networking
Virtual Private Cloud
Elastic IP
Elastic Load Balance
NAT Gateway
Direct Connect
Virtual Private Network
VPC Endpoint
Cloud Connect
Enterprise Router
Enterprise Switch
Global Accelerator
Management & Governance
Cloud Eye
Identity and Access Management
Cloud Trace Service
Resource Formation Service
Tag Management Service
Log Tank Service
Config
OneAccess
Resource Access Manager
Simple Message Notification
Application Performance Management
Application Operations Management
Organizations
Optimization Advisor
IAM Identity Center
Cloud Operations Center
Resource Governance Center
Migration
Server Migration Service
Object Storage Migration Service
Cloud Data Migration
Migration Center
Cloud Ecosystem
KooGallery
Partner Center
User Support
My Account
Billing Center
Cost Center
Resource Center
Enterprise Management
Service Tickets
HUAWEI CLOUD (International) FAQs
ICP Filing
Support Plans
My Credentials
Customer Operation Capabilities
Partner Support Plans
Professional Services
Analytics
MapReduce Service
Data Lake Insight
CloudTable Service
Cloud Search Service
Data Lake Visualization
Data Ingestion Service
GaussDB(DWS)
DataArts Studio
Data Lake Factory
DataArts Lake Formation
IoT
IoT Device Access
Others
Product Pricing Details
System Permissions
Console Quick Start
Common FAQs
Instructions for Associating with a HUAWEI CLOUD Partner
Message Center
Security & Compliance
Security Technologies and Applications
Web Application Firewall
Host Security Service
Cloud Firewall
SecMaster
Anti-DDoS Service
Data Encryption Workshop
Database Security Service
Cloud Bastion Host
Data Security Center
Cloud Certificate Manager
Edge Security
Managed Threat Detection
Blockchain
Blockchain Service
Web3 Node Engine Service
Media Services
Media Processing Center
Video On Demand
Live
SparkRTC
MetaStudio
Storage
Object Storage Service
Elastic Volume Service
Cloud Backup and Recovery
Storage Disaster Recovery Service
Scalable File Service Turbo
Scalable File Service
Volume Backup Service
Cloud Server Backup Service
Data Express Service
Dedicated Distributed Storage Service
Containers
Cloud Container Engine
SoftWare Repository for Container
Application Service Mesh
Ubiquitous Cloud Native Service
Cloud Container Instance
Databases
Relational Database Service
Document Database Service
Data Admin Service
Data Replication Service
GeminiDB
GaussDB
Distributed Database Middleware
Database and Application Migration UGO
TaurusDB
Middleware
Distributed Cache Service
API Gateway
Distributed Message Service for Kafka
Distributed Message Service for RabbitMQ
Distributed Message Service for RocketMQ
Cloud Service Engine
Multi-Site High Availability Service
EventGrid
Dedicated Cloud
Dedicated Computing Cluster
Business Applications
Workspace
ROMA Connect
Message & SMS
Domain Name Service
Edge Data Center Management
Meeting
AI
Face Recognition Service
Graph Engine Service
Content Moderation
Image Recognition
Optical Character Recognition
ModelArts
ImageSearch
Conversational Bot Service
Speech Interaction Service
Huawei HiLens
Video Intelligent Analysis Service
Developer Tools
SDK Developer Guide
API Request Signing Guide
Terraform
Koo Command Line Interface
Content Delivery & Edge Computing
Content Delivery Network
Intelligent EdgeFabric
CloudPond
Intelligent EdgeCloud
Solutions
SAP Cloud
High Performance Computing
Developer Services
ServiceStage
CodeArts
CodeArts PerfTest
CodeArts Req
CodeArts Pipeline
CodeArts Build
CodeArts Deploy
CodeArts Artifact
CodeArts TestPlan
CodeArts Check
CodeArts Repo
Cloud Application Engine
MacroVerse aPaaS
KooMessage
KooPhone
KooDrive

Routinely Maintaining Tables

Updated on 2022-07-29 GMT+08:00

To ensure proper database running, after INSERT and DELETE operations, you need to routinely do VACUUM FULL and ANALYZE as appropriate for customer scenarios and update statistics to obtain better performance.

Related Concepts

You need to routinely run VACUUM, VACUUM FULL, and ANALYZE to maintain tables, because:

  • VACUUM FULL reclaims disk space occupied by updated or deleted data and combines small-size data files.
  • VACUUM maintains a visualized mapping to track pages that contain arrays visible to other active transactions. A common index scan uses the mapping to obtain the corresponding array and check whether pages are visible to the current transaction. If the array cannot be obtained, the visibility is checked by fetching stack arrays. Therefore, updating the visible mapping of a table can accelerate unique index scans.
  • VACUUM can avoid old data loss caused by duplicate transaction IDs when the number of executed transactions exceeds the database threshold.
  • ANALYZE collects statistics on tables in databases. The statistics are stored in the PG_STATISTIC system catalog. Then, the query optimizer uses the statistics to work out the most efficient execution plan.

Procedure

  1. Run the VACUUM or VACUUM FULL command to reclaim disk space.

    • VACUUM:
      Do VACUUM to the table:
      VACUUM customer;
      VACUUM

      This command can be concurrently executed with database operation commands, including SELECT, INSERT, UPDATE, and DELETE; excluding ALTER TABLE.

      Do VACUUM to the partitioned table:

      VACUUM customer_par PARTITION ( P1 );
      VACUUM
    • VACUUM FULL:
      VACUUM FULL customer;
      VACUUM

      VACUUM FULL needs to add exclusive locks on tables it operates on and requires that all other database operations be suspended.

      When reclaiming disk space, you can query for the session corresponding to the earliest transactions in the cluster, and then end the earliest long transactions as needed to make full use of the disk space.

      1. Run the following command to query for oldestxmin on the GTM:
        select * from pgxc_gtm_snapshot_status();
      2. Run the following command to query for the PID of the corresponding session on the CN. xmin is the oldestxmin obtained in the previous step.
        select * from pgxc_running_xacts() where xmin=1400202010;

  2. Do ANALYZE to update statistical information.

    ANALYZE customer;
    ANALYZE

    Do ANALYZE VERBOSE to update statistics and display table information.

    ANALYZE VERBOSE customer;
    ANALYZE

    You can use VACUUM ANALYZE at the same time to optimize the query.

    VACUUM ANALYZE customer;
    VACUUM
    NOTE:

    VACUUM and ANALYZE cause a substantial increase in I/O traffic, which may cause poor performance of other active sessions. Therefore, you are advised to set by specifying the vacuum_cost_delay parameter.

  3. Delete a table

    DROP TABLE customer;
    DROP TABLE customer_par;
    DROP TABLE part;

    If the following output is displayed, the index has been deleted.

    DROP TABLE

Maintenance Suggestion

  • Routinely do VACUUM FULL to large tables. If the database performance deteriorates, do VACUUM FULL to the entire database. If the database performance is stable, you are advised to monthly do VACUUM FULL.
  • Routinely do VACUUM FULL to system catalogs, mainly PG_ATTRIBUTE.
  • The automatic vacuum process (AUTOVACUUM) in the system automatically runs the VACUUM and ANALYZE statements to reclaim the record space marked as the deleted state and to update statistics related to the table.

We use cookies to improve our site and your experience. By continuing to browse our site you accept our cookie policy. Find out more

Feedback

Feedback

Feedback

0/500

Selected Content

Submit selected content with the feedback