Deze pagina is nog niet beschikbaar in uw eigen taal. We werken er hard aan om meer taalversies toe te voegen. Bedankt voor uw steun.
Document Database Service
Document Database Service
- What's New
- Function Overview
- Service Overview
-
Getting Started
- Overview
- Getting Started with Clusters
- Getting Started with Replica Sets
- Getting Started with Single Nodes
- Logging In to the DDS Console
- Example: Buying and Connecting to a DDS Instance
- Change History (Getting Started) Europe Site
-
User Guide
- Migrating Data
- Performance Tuning
- Permissions Management
- Instance Lifecycle Management
- Instance Modifications
- Data Backups
- Data Restorations
-
Parameter Template Management
- Overview
- Creating a Parameter Template
- Modifying a Parameter Template
- Viewing Parameter Change History
- Exporting a Parameter Template
- Comparing Parameter Templates
- Replicating a Parameter Template
- Resetting a Parameter Template
- Applying a Parameter Template
- Viewing Application Records of a Parameter Template
- Modifying the Description of a Parameter Template
- Deleting a Parameter Template
- Connection Management
- Database Usage
- Data Security
- Monitoring and Alarm Reporting
- Auditing
- Logs
- Task Center
- Billing
- Tags
- Quotas
- DDS Usage Suggestions
- Change History
- Developer Guide
-
Best Practices
- Overview
- Common Methods for Connecting to a DDS Instance
- How Do Replica Sets Achieve High Availability and Read/Write Splitting?
- Sharding
- How Do I Improve DDS Performance by Optimizing SQL Statements?
- How Do I Prevent the Mongos Cache Problem?
- How Do I Solve the High CPU Usage Issue?
- Creating a User and Granting the Read-Only Permission to the User
- Security White Paper
- Performance White Paper
-
API Reference
- Before You Start
- API Overview
- Calling APIs
- Getting Started
-
APIs V3.0 (Recommended)
- Querying the API Version
- Querying Database Version Information
- Querying Database Specifications
- Querying the Database Disk Type
-
DB Instance Management
- Creating a DB Instance
- Restarting a DB Instance
- Deleting a DB Instance
- Querying Instances and Details
- Scaling Up Storage Space
- Adding Nodes for a Cluster Instance
- Modifying DB Instance Specifications
- Performing a Primary/Secondary Switchover in a Replica Set Instance
- Enabling or Disabling SSL
- Modifying a DB Instance Name
- Changing an Instance Description
- Changing a Database Port
- Changing a Security Group
- Binding an EIP
- Unbinding an EIP
- Changing a Private IP Address
- Creating Shard or Config IP Addresses of a Cluster Instance
- Configuring Cross-CIDR Access for a Replica Set
- Querying AZs to Which an Instance Can Be Migrated
- Migrating a DB Instance to Another AZ
- Adding Nodes to a Replica Set Instance
- Adding a Read Replica to an Instance
- Connection Management
-
Backup and Restoration
- Creating a Manual Backup
- Deleting a Manual Backup
- Querying the Backup List
- Querying an Automated Backup Policy
- Setting an Automated Backup Policy
- Restoring Data to a New DB Instance
- Obtaining the Link for Downloading a Backup File
- Querying the Restoration Time Ranges
- Obtaining the List of Databases That Can Be Restored
- Obtaining the List of Database Collections That Can Be Restored
- Restoring Data to the Original DB Instance
- Restoring Databases and Tables to a Point in Time
- Parameter Configuration
- Log Information Queries
- Tag Management
-
Managing Databases and Users
- Creating a Database User
- Creating a Database Role
- Querying Details About Database Users
- Querying the Database Role List
- Changing the Password of a Database User
- Checking the Password for Logging In to a Database
- Querying Cluster Balancing Settings
- Enabling or Disabling Cluster Balancing
- Setting the Activity Time Window for Cluster Balancing
- Deleting a Database User
- Deleting a Database Role
- Quota Management
- Task Management
- API V3 (Unavailable Soon)
- Examples
- Permissions Policies and Supported Actions
- Appendix
- Change History (European Sites)
- SDK Reference
-
FAQs
-
Product Consulting
- What Is the Relationship Between DDS and MongoDB Community Edition?
- What Are the Differences Between DDS and GaussDB(for Mongo)?
- What Precautions Should Be Taken When Using DDS?
- What Is the Availability of DDS DB Instances?
- Will My DDS DB Instances Be Affected by Other Users' DDS DB Instances?
- Does DDS Support Multi-AZ Deployment?
- Can I Change the VPC for a Created Instance?
- Can I Change the Region for a Created Instance?
- What Is Hidden Node?
- Database Versions
-
Resource and Disk Management
- Which Items Occupy the Storage Space of DDS Instances?
- Which Types of Logs and Files Occupy DDS DB Instance Storage Space?
- Why Is the Storage Space Usage Displayed on the GUI Smaller Than the Actual Usage?
- Why Does Available Disk Space Not Increase After Data Is Deleted?
- Why Is the Resident Memory of a 4 vCPUs/8 GB Memory Replica Set Instance Only 4 GB?
- Capacity Expansion and Specification Changes
-
Database Performance
- When Will a Primary/Standby Switchover Be Triggered for a Cluster or Replica Set?
- High Storage Usage
- What Is the Time Delay for Primary/Secondary Synchronization in a Replica Set?
- How Is Data Transferred Between the Primary and Secondary Nodes of a Replica Set?
- How Do I Clear an Alarm Saying the Shard Memory Usage Exceeds 90%?
- What Can I Do If a Query Error Is Reported After Data Is Written Into the DDS Cluster?
- Database Permissions
-
Creation and Deletion
- How Do I Select Instance Specifications and Nodes?
- Why Is an Instance Not Displayed on the Console After It Is Created?
- Can I Use a Template to Create DDS DB Instances?
- Why Is Data Missing from My Database?
- Will My Backups Be Deleted If I Delete My Cloud Account?
- What Are the Differences Between Instance Deletion and Unsubscription?
-
Database Connection
- What Should I Do If I Fail to Connect to a DDS Instance?
- What Can I Do If the Number of Connections of an Instance Reaches Its Maximum?
- How Do I Query and Limit the Number of Connections?
- What Should I Do If the ECS and DDS Are Deployed in Different VPCs and They Cannot Communicate with Each Other?
- Do Applications Need to Support Automatic Reconnecting to the DDS Database?
- How Do I Create and Log In to an ECS?
- Installing a Client
- Database Usage
- Database Migration
- Database Storage
- Database Parameters
- Backup and Restoration
- Network Security
- Monitoring and Alarm
- Change History (FAQs) Europe Site
-
Product Consulting
-
Troubleshooting
- DDS Instance Node Fault Handling Mechanism
- Connection Failure Message: network error while attempting to run command 'isMaster'
- Connection Failure Messages: No route to host and connection attempt failed
- Connection Failure Message: Authentication failed
- Connection Failure Message: couldn't connect to server
- Connection Failure Message: cannot list multiple servers in URL without 'replicaSet' option
- Connection Failure Message: Timeout while receiving message
- Connection Failure Message: exception: login failed and U_STRINGPREP_PROHIBITED_ERROR
- Change History (Troubleshooting) European Sites
- Videos
On this page
Show all
Help Center/
Document Database Service/
Developer Guide/
Database Usage Suggestions/
Basic Commands/
Query
Query
Updated on 2022-09-21 GMT+08:00
To avoid slow queries, analyze and optimize the execution process (query plan).
db.collection.find().explain()
For details, see Performance and official documents.
Precaution
- The returned query result is a cursor. After using the cursor, close it in time. Otherwise, memory leaks accumulate.
- Create necessary indexes based on search criteria. For details about index design, see Index.
- Do not use COLLSCAN to scan the entire table.
- Query conditions and index fields are matched in sequence.
- For cluster instances, shard tables properly based on service requirements. For details about sharding, see Sharding.
- For sharded tables, query conditions must be based on shard keys to avoid unnecessary queries such as scatter-gather. For details, see Distributed Queries.
- You can specify a readConcern level for queries. For details, see Read Concern.
- You can specify the readPerference parameter for queries. For details, see Read Preference.
Parent topic: Basic Commands
Feedback
Was this page helpful?
Provide feedbackThank you very much for your feedback. We will continue working to improve the documentation.
The system is busy. Please try again later.
