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Home

Technical Articles

Database

Redis

Redis vs Traditional DB: Best code practices

Redisisidealforspeedandreal-timedataprocessing,whiletraditionaldatabaseslikeMySQLorPostgreSQLarebetterforcomplextransactionsanddataintegrity.1)UseRedisforcaching,real-timeanalytics,andsessionmanagementwithappropriatedatastructuresandexpirationtimes.2

Sep 02, 2025 am 02:09 AM

redis database

What is the difference between SUNION and SUNIONSTORE?

The main difference between SUNION and SUNIONSTORE is the way of processing the result. 1.SUNION is used to return union elements of multiple collections, without modifying data, and is suitable for temporary viewing of results; 2.SUNIONSTORE stores union results in a new key, and is suitable for scenarios where persistent results are required. Both times have O(N), but SUNIONSTORE may have a greater impact on performance due to write operations. You should pay attention to memory usage and execution timing when using it.

Sep 02, 2025 am 12:12 AM

redis Set operations

What is the purpose of the requirepass configuration directive?

TherequirepassdirectiveinRedisisusedtosetapasswordforclientauthentication.1.ItensuresthatonlyuserswhoknowthepasswordcaninteractwiththeRedisinstanceafterconnecting.2.Itisconfiguredbyeditingtheredis.conffileandspecifyingthepasswordwithrequirepassyour_s

Sep 01, 2025 am 03:42 AM

redis

What is the difference between RDB and AOF persistence in Redis?

Redis provides two persistence mechanisms: RDB and AOF. 1. RDB saves data through timed snapshots, which is suitable for backup and fast recovery, but may lose data for several minutes; 2. AOF records every write operation, and the data is safer, but the file is larger and the recovery is slower. In most scenarios, it is recommended to enable both to take into account performance and security. If you pursue zero data loss, you should choose AOF. If you accept occasional loss and need to recover quickly, you should choose RDB.

Sep 01, 2025 am 02:07 AM

Can you run a command that accesses multiple keys on a Redis Cluster?

Yes, you can run commands to access multiple keys on RedisCluster, but with some limitations. RedisCluster distributes keys to different nodes through data sharding, so if a command requires multiple keys to operate, these keys must be on the same node to be executed. 1. Prerequisite for supporting multi-key operations: the key must divide the data into 16384 hash slots (hashslots) in the same slot, and each key is mapped to a slot according to its hash value. Only when multiple keys are mapped to the same slo

Aug 31, 2025 am 03:03 AM

多鍵訪問

How to find points within a specific radius using GEORADIUS?

To use the GEORADIUS command in Redis to find geographical points within a specified radius, you must first add data through GEOADD, then execute GEORADIUS for querying and combine parameter expansion functions. 1. Use the GEOADD command to add geographic location data, such as the GEOADDcities latitude and longitude city name; 2. Use the GEORADIUS command to query by radius, the format is GEORADIUSkey latitude and longitude radius units; 3. You can select WITHCOORD and WITHDIST to obtain latitude and longitude and distance information; 4. Use COUNT to limit the number of returns and sort through ASC/DESC; 5. Pay attention to the latitude and longitude order, and do not directly modify the performance under stored data and large data volumes.

Aug 31, 2025 am 01:18 AM

What is the trade-off when using HyperLogLog? (space vs. accuracy)

HyperLogLogtradesaccuracyforspaceefficiencybyusingprobabilisticmethodstoestimateuniqueelementsinlargedatasets.Insteadofstoringallitems,ithashesvaluesandtracksleadingzerostoinfercardinalitywithminimalmemory—kilobytesinsteadofgigabytes.Thisintroducesan

Aug 30, 2025 am 08:56 AM

trade off

What are blocking list pop operations like BLPOP and BRPOP?

BLPOPandBRPOPareblockinglistcommandsinRedisusedtoretrieveandremoveelementsfromalist,waitingifnecessaryuntilanelementisavailableoratimeoutoccurs.BLPOPpopsfromtheleft(head)ofthelist,whileBRPOPpopsfromtheright(tail).Theyareidealfortaskqueuesandreal-time

Aug 30, 2025 am 06:36 AM

阻塞列表彈出操作

What is the GETDEL command introduced in Redis 6.2?

GETDEL was introduced in Redis 6.2 to atomically obtain and delete string keys. 1. It combines the GET and DEL that originally required two operations into one to avoid concurrent interference; 2. Return the value and delete it if the key exists, otherwise it returns nil; 3. Applicable to scenes such as one-time tokens, light queues, and deletion after fetching; 4. Only support string types, efficient operation and atomicity, and is suitable for use in high-concurrency environments.

Aug 29, 2025 am 07:35 AM

What are the key metrics to monitor for a healthy Redis instance?

TokeepaRedisinstancehealthy,monitorkeymetricsinthefollowingorder:1.Memoryusage,trackingused_memoryandused_memory_rsswhileapproachingsystemRAMlimits,andmanagingitviamaxmemory,evictionpolicies,efficientdatastructures,andcompression;2.CPUutilization,mon

Aug 29, 2025 am 06:38 AM

redis Monitoring indicators

How are Redis keys passed to a Lua script?

TouseRediskeysinLuascripts,passthemviatheKEYSglobalvariable.1.KEYSisanarray-liketableaccessibleinLuascriptsrunningonRedis.2.KeysarepassedusingEVALorEVALSHAcommandsbyspecifyingthecountfollowedbykeynames.3.AccesskeysinLuaasKEYS[1],KEYS[2],etc.,whichref

Aug 28, 2025 am 09:18 AM

What is the EXISTS command used for?

The EXISTS command in SQL is used to check if there is a record in a subquery, it returns a boolean value instead of the actual data. Its core purpose is to improve performance based on whether relevant data filtering results exist in another table, especially when processing large data sets. Common uses include: 1. Filter records based on associated data, such as finding customers with orders; 2. It is more efficient than IN or JOIN because it has an early exit mechanism, avoids duplicate processing and has clearer logic; 3. Use NOTEXISTS to find missing associations, such as customers who have not placed an order, for data cleaning and integrity verification. In short, EXISTS is suitable for existence inspection scenarios, emphasizing judgment rather than data retrieval.

Aug 28, 2025 am 09:10 AM

How Do I Set Up Redis to Start Automatically on Boot in Linux?

RediscanbesetuptostartautomaticallyonbootinLinuxusingsystemd.1)InstallRedisusingyourpackagemanager.2)EnabletheRedisservicewith'sudosystemctlenableredis-server'.3)Starttheservicetotestwith'sudosystemctlstartredis-server',andcheckitsstatuswith'sudosyst

Aug 27, 2025 am 04:32 AM

How does Redis handle a restart when both RDB and AOF are enabled?

WhenRedisrestartswithbothRDBandAOFenabled,theAOFfiletakespriorityfordatarecoverybecauseitoffersgreaterdurabilitybyloggingeverywriteoperation.1.RedisfirstchecksforthepresenceofanAOFfileandloadsdatafromitifavailable.2.IftheAOFfileiscorruptedorempty,Red

Aug 27, 2025 am 01:23 AM