1. Description
zset is an ordered set, and the key of zset is non-repeatable.
2. Function
Commonly used for functions such as rankings
3. Use commands
1. Add: zadd
zadd [ redis_key ] [ zset_key ] [ zset_value ] …
example:
zadd player 99 Xiaobai 87 Xiaohong 2.5 Wutiao
2. Delete: zrem
Example: Delete Xiaohong
zrem player 小红
3. Increase scores: zincrby
zincrby [ redis_key ] [ zset_key ] [ zset_value ]
Example: Add Xiaobai’s 99 points + 100 points.
zincrby player 1 小白
4. Subscript range query: zrange
zrange [ redis_key ] [zset start subscript] [zset end subscript] [withscores]
Example: Traverse from the first to the last. Defaults to ascending in zset.
zrange player 0 -1 zrange player 0 -1 withscores
Without withscores, only the values of zset are output.
Add withscores to output the values and keys of zset.
5. Score range query: zrangebyscore
zrangebyscore [ redis_key ] [zset minimum score] [zset maximum score] [withscores]
Example: Query players with scores from 2 to 5. Ascending order.
zrangebyscore player 2 5 zrangebyscore player 2 5 withscores
If the minimum score and the maximum score swap places, descending order can be achieved.
Example: Query players with scores from 2 to 5. Descending order.
zrangebyscore player 5 2
6. Score range statistics: zcount
zcount [ redis_key ] [zset minimum score] [zset maximum score]
Example: Count the total number of people who match the score from 2 to 5
zcount player 2 5
7. Get the subscript: zrank
zrank [ redis_key ] [zset value]
zrank player 五条
You can achieve search ranking through this function.
8. Query the total number of zsets
**zcard [redis_key] **
zcard player
Related documents
4. Underlying data structure – ziplist and skiplist
The bottom layer of zset is implemented by ziplist and skiplist.
When the number of elements stored in zset <= 128 and the size of each element <= 64 bytes, use ziplist, otherwise use skiplist.
1. ziplist skip list structure
struct ziplist<T> {<!-- -->
int32 zlbytes;//Memory usage; used when reallocating compressed list memory or calculating the position of zlend.
int32 zltail_offset;
int16 zllength; //The number of nodes, when it is less than 65535, is the real number; when it is equal to 65535, it must be traversed and calculated.
T[] entries;
int8 zlend; //0xFF, used to mark the end of the compressed list
}
struct entry {<!-- -->
int<var> prevlen; // The byte length of the previous entry
int<var> encoding; // element type encoding
optional byte[] content; // element content
}
2. skiplist structure
typedef struct zset{<!-- -->
//jump table
zskiplist *zsl;
//Dictionary key saves member, value saves score;
dict *dice;
} zset;
// Jump table
typedef struct zskiplist {<!-- -->
struct zskiplistNode *header, *tail;
unsigned long length; //skip table length
int level; //Maximum level of jump table index node
} zskiplist;
// Jump table node
typedef struct zskiplistNode {<!-- -->
sds ele; //member member
double score; //score
struct zskiplistNode *backward; //Previous node pointer
struct zskiplistLevel {<!-- -->
struct zskiplistNode *forward; //Next node pointer, used to implement multi-layer linked lists.
unsigned long span; //Record the distance between two nodes, used to calculate rank ranking
} level[];
} zskiplistNode;
Add logic
void zaddGenericCommand(redisClient *c, int incr) {<!-- -->
static char *nanerr = "resulting score is not a number (NaN)";
robj *key = c->argv[1];
robj *ele;
robj *zobj;
robj *curobj;
double score = 0, *scores = NULL, curscore = 0.0;
int j, elements = (c->argc-2)/2;
int added = 0, updated = 0;
//The input score - member parameters must appear in pairs
if (c->argc % 2) {<!-- -->
addReply(c,shared.syntaxerr);
return;
}
// Get all input score values
scores = zmalloc(sizeof(double)*elements);
for (j = 0; j < elements; j + + ) {<!-- -->
if (getDoubleFromObjectOrReply(c,c->argv[2 + j*2], & amp;scores[j],NULL)
!= REDIS_OK) goto cleanup;
}
// Get the ordered collection object
zobj = lookupKeyWrite(c->db,key);
if (zobj == NULL) {<!-- -->
//The ordered set does not exist, create a new ordered set
if (server.zset_max_ziplist_entries == 0 ||
server.zset_max_ziplist_value < sdslen(c->argv[3]->ptr))
{<!-- -->
zobj = createZsetObject();
} else {<!-- -->
zobj = createZsetZiplistObject();
}
//Associate objects to the database
dbAdd(c->db,key,zobj);
} else {<!-- -->
//Object exists, check type
if (zobj->type != REDIS_ZSET) {<!-- -->
addReply(c,shared.wrongtypeerr);
goto cleanup;
}
}
// process all elements
for (j = 0; j < elements; j + + ) {<!-- -->
score = scores[j];
// Sorted collection is ziplist encoded
if (zobj->encoding == REDIS_ENCODING_ZIPLIST) {<!-- -->
unsigned char *eptr;
// Find members
ele = c->argv[3 + j*2];
if ((eptr = zzlFind(zobj->ptr,ele, & amp;curscore)) != NULL) {<!-- -->
// member already exists
// Used when using ZINCRYBY command
if (incr) {<!-- -->
score + = curscore;
if (isnan(score)) {<!-- -->
addReplyError(c,nanerr);
goto cleanup;
}
}
//When executing the ZINCRYBY command,
// Or executed when the user modifies the member's score through ZADD
if (score != curscore) {<!-- -->
// Delete existing elements
zobj->ptr = zzlDelete(zobj->ptr,eptr);
// reinsert element
zobj->ptr = zzlInsert(zobj->ptr,ele,score);
// counter
server.dirty + + ;
updated + + ;
}
} else {<!-- -->
//The element does not exist, add it directly
zobj->ptr = zzlInsert(zobj->ptr,ele,score);
// Check the number of elements,
// See if you need to convert the ZIPLIST encoding into an ordered set
if (zzlLength(zobj->ptr) > server.zset_max_ziplist_entries)
zsetConvert(zobj,REDIS_ENCODING_SKIPLIST);
// Check the length of the newly added element
// See if you need to convert the ZIPLIST encoding into an ordered set
if (sdslen(ele->ptr) > server.zset_max_ziplist_value)
zsetConvert(zobj,REDIS_ENCODING_SKIPLIST);
server.dirty + + ;
added + + ;
}
// Sorted set is SKIPLIST encoded
} else if (zobj->encoding == REDIS_ENCODING_SKIPLIST) {<!-- -->
zset *zs = zobj->ptr;
zskiplistNode *znode;
dictEntry *de;
// encoding object
ele = c->argv[3 + j*2] = tryObjectEncoding(c->argv[3 + j*2]);
// Check if the member exists
de = dictFind(zs->dict,ele);
if (de != NULL) {<!-- -->
//member exists
//retrieve members
curobj = dictGetKey(de);
// Get the score
curscore = *(double*)dictGetVal(de);
// Execute when ZINCRYBY
if (incr) {<!-- -->
score + = curscore;
if (isnan(score)) {<!-- -->
addReplyError(c,nanerr);
goto cleanup;
}
}
//When executing the ZINCRYBY command,
// Or executed when the user modifies the member's score through ZADD
if (score != curscore) {<!-- -->
// Delete the original element
redisAssertWithInfo(c,curobj,zslDelete(zs->zsl,curscore,curobj));
// reinsert element
znode = zslInsert(zs->zsl,score,curobj);
incrRefCount(curobj); /* Re-inserted in skiplist. */
//Update the score pointer of the dictionary
dictGetVal(de) = & amp;znode->score; /* Update score ptr. */
server.dirty + + ;
updated + + ;
}
} else {<!-- -->
// If the element does not exist, add it directly to the jump list
znode = zslInsert(zs->zsl,score,ele);
incrRefCount(ele); /* Inserted in skiplist. */
//Associate the element to the dictionary
redisAssertWithInfo(c,NULL,dictAdd(zs->dict,ele, & amp;znode->score) == DICT_OK);
incrRefCount(ele); /* Added to dictionary. */
server.dirty + + ;
added + + ;
}
} else {<!-- -->
redisPanic("Unknown sorted set encoding");
}
}
if (incr) /* ZINCRBY */
addReplyDouble(c,score);
else /* ZADD */
addReplyLongLong(c,added);
cleanup:
zfree(scores);
if (added || updated) {<!-- -->
signalModifiedKey(c->db,key);
notifyKeyspaceEvent(REDIS_NOTIFY_ZSET,
incr ? "zincr" : "zadd", key, c->db->id);
}
}
//https://blog.csdn.net/qq_27198345/article/details/108674817