在Redis源码解读（二）——启动流程中，启动事件驱动框架之前，会初始化Server，中间有一步会初始化Redis的数据库：
void initServer(void) {
...
for (j = 0; j < server.dbnum; j++) {
server.db[j].dict = dictCreate(&dbDictType,NULL);
server.db[j].expires = dictCreate(&keyptrDictType,NULL);
server.db[j].blocking_keys = dictCreate(&keylistDictType,NULL);
server.db[j].ready_keys = dictCreate(&objectKeyPointerValueDictType,NULL);
server.db[j].watched_keys = dictCreate(&keylistDictType,NULL);
server.db[j].id = j;
server.db[j].avg_ttl = 0;
server.db[j].defrag_later = listCreate();
}
...
}
struct redisServer {
...
redisDb *db;
...
};db在redisServer中是个redisDb的数组，数组默认大小是16，通过select命令选择不同的db，db初始化之后，就可以存储用户命令发送的KV对了。
redisDb
redisDb结构：
typedef struct redisDb {
dict *dict; /* The keyspace for this DB */
dict *expires; /* Timeout of keys with a timeout set */
dict *blocking_keys; /* Keys with clients waiting for data (BLPOP)*/
dict *ready_keys; /* Blocked keys that received a PUSH */
dict *watched_keys; /* WATCHED keys for MULTI/EXEC CAS */
int id; /* Database ID */
long long avg_ttl; /* Average TTL, just for stats */
list *defrag_later; /* List of key names to attempt to defrag one by one, gradually. */
} redisDb;本节先看dict、expires和id这三个字段，其他的几个在后面会详细介绍。
dict是db的存储空间，用来存储所有的KV对
expires用来存储所有待过期时间的KV对
id是该redisDb在redisServer的数组下标
redisObject
dict中存储的key是sds，value是robj*，robj结构如下：
typedef struct redisObject {
unsigned type:4;
unsigned encoding:4;
unsigned lru:LRU_BITS; /* LRU time (relative to global lru_clock) or
* LFU data (least significant 8 bits frequency
* and most significant 16 bits access time). */
int refcount;
void *ptr;
} robj;redisObject采用位域定义：
type：robj类型，也就是我们常说的五种：
#define OBJ_STRING 0 /* String object. */
#define OBJ_LIST 1 /* List object. */
#define OBJ_SET 2 /* Set object. */
#define OBJ_ZSET 3 /* Sorted set object. */
#define OBJ_HASH 4 /* Hash object. */encoding：robj编码方式，同一种类型会有不同的编码方式，五种基本类型对应的编码方式如下：
OBJ_STRING：OBJ_ENCODING_RAW、OBJ_ENCODING_INT、OBJ_ENCODING_EMBSTR
OBJ_LIST：OBJ_ENCODING_ZIPLIST、OBJ_ENCODING_QUICKLIST
OBJ_SET：OBJ_ENCODING_INTSET、OBJ_ENCODING_HT
OBJ_ZSET：OBJ_ENCODING_ZIPLIST、OBJ_ENCODING_SKIPLIST
OBJ_HASH：OBJ_ENCODING_ZIPMAP、OBJ_ENCODING_HT#define OBJ_ENCODING_RAW 0 /* Raw representation */
#define OBJ_ENCODING_INT 1 /* Encoded as integer */
#define OBJ_ENCODING_HT 2 /* Encoded as hash table */
#define OBJ_ENCODING_ZIPMAP 3 /* Encoded as zipmap */
#define OBJ_ENCODING_LINKEDLIST 4 /* No longer used: old list encoding. */
#define OBJ_ENCODING_ZIPLIST 5 /* Encoded as ziplist */
#define OBJ_ENCODING_INTSET 6 /* Encoded as intset */
#define OBJ_ENCODING_SKIPLIST 7 /* Encoded as skiplist */
#define OBJ_ENCODING_EMBSTR 8 /* Embedded sds string encoding */
#define OBJ_ENCODING_QUICKLIST 9 /* Encoded as linked list of ziplists */
#define OBJ_ENCODING_STREAM 10 /* Encoded as a radix tree of listpacks */lru：24bit，为了支持键的淘汰，本节先不讲
refcount：robj的引用计数，控制robj的生命周期，当refcount减少到0时，就可以释放robj：
void incrRefCount(robj *o) {
if (o->refcount != OBJ_SHARED_REFCOUNT) o->refcount++;
}
void decrRefCount(robj *o) {
if (o->refcount == 1) {
switch(o->type) {
case OBJ_STRING: freeStringObject(o); break;
case OBJ_LIST: freeListObject(o); break;
case OBJ_SET: freeSetObject(o); break;
case OBJ_ZSET: freeZsetObject(o); break;
case OBJ_HASH: freeHashObject(o); break;
case OBJ_MODULE: freeModuleObject(o); break;
case OBJ_STREAM: freeStreamObject(o); break;
default: serverPanic("Unknown object type"); break;
}
zfree(o);
} else {
if (o->refcount <= 0) serverPanic("decrRefCount against refcount <= 0");
if (o->refcount != OBJ_SHARED_REFCOUNT) o->refcount--;
}
}ptr：是一个void*指针，指向robj中的value
单机数据库的实现
redisDb相关的API实现都在db.c中，提供给各个命令的API使用，在Redis源码解读（四）——命令端到端的过程中，用户的命令会解析成token存在client中，然后查找到命令对应的处理函数之后，就会调用命令处理函数对db进行操作，下面就介绍五种基本类型的实现。
Redis所有的命令：https://www.redis.net.cn/order/。本节先介绍与数据库有关的命令，每个命令的处理函数可以参考server.c中的redisCommandTable命令数组。
字符串命令实现
与字符串有关的命令实现在t_string.c中，这里解析两个：set、get，其他的命令实现都大差不差。
set:
void setCommand(client *c) {
int j;
robj *expire = NULL;
int unit = UNIT_SECONDS;
int flags = OBJ_SET_NO_FLAGS;
// 对set命令待的参数进行解析，比如nx、ex、px等key过期时间
for (j = 3; j < c->argc; j++) {
char *a = c->argv[j]->ptr;
robj *next = (j == c->argc-1) ? NULL : c->argv[j+1];
if ((a[0] == 'n' || a[0] == 'N') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
!(flags & OBJ_SET_XX))
{
flags |= OBJ_SET_NX;
} else if ((a[0] == 'x' || a[0] == 'X') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
!(flags & OBJ_SET_NX))
{
flags |= OBJ_SET_XX;
} else if ((a[0] == 'e' || a[0] == 'E') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
!(flags & OBJ_SET_PX) && next)
{
flags |= OBJ_SET_EX;
unit = UNIT_SECONDS;
expire = next;
j++;
} else if ((a[0] == 'p' || a[0] == 'P') &&
(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
!(flags & OBJ_SET_EX) && next)
{
flags |= OBJ_SET_PX;
unit = UNIT_MILLISECONDS;
expire = next;
j++;
} else {
addReply(c,shared.syntaxerr);
return;
}
}
c->argv[2] = tryObjectEncoding(c->argv[2]);
setGenericCommand(c,flags,c->argv[1],c->argv[2],expire,unit,NULL,NULL);
}先对set命令携带的额外参数解析，主要是key的过期时间，然后调用tryObjectEncoding尝试对value进行编码，即设置robj中的encoding字段：
robj *tryObjectEncoding(robj *o) {
...
// 尝试OBJ_ENCODING_INT编码
if (len <= 20 && string2l(s,len,&value)) {
/* This object is encodable as a long. Try to use a shared object.
* Note that we avoid using shared integers when maxmemory is used
* because every object needs to have a private LRU field for the LRU
* algorithm to work well. */
if ((server.maxmemory == 0 ||
!(server.maxmemory_policy & MAXMEMORY_FLAG_NO_SHARED_INTEGERS)) &&
value >= 0 &&
value < OBJ_SHARED_INTEGERS)
{
decrRefCount(o);
incrRefCount(shared.integers[value]);
return shared.integers[value];
} else {
if (o->encoding == OBJ_ENCODING_RAW) {
sdsfree(o->ptr);
o->encoding = OBJ_ENCODING_INT;
o->ptr = (void*) value;
return o;
} else if (o->encoding == OBJ_ENCODING_EMBSTR) {
decrRefCount(o);
return createStringObjectFromLongLongForValue(value);
}
}
}
/* If the string is small and is still RAW encoded,
* try the EMBSTR encoding which is more efficient.
* In this representation the object and the SDS string are allocated
* in the same chunk of memory to save space and cache misses. */
// 尝试OBJ_ENCODING_EMBSTR编码
if (len <= OBJ_ENCODING_EMBSTR_SIZE_LIMIT) {
robj *emb;
if (o->encoding == OBJ_ENCODING_EMBSTR) return o;
emb = createEmbeddedStringObject(s,sdslen(s));
decrRefCount(o);
return emb;
}
/* We can't encode the object...
*
* Do the last try, and at least optimize the SDS string inside
* the string object to require little space, in case there
* is more than 10% of free space at the end of the SDS string.
*
* We do that only for relatively large strings as this branch
* is only entered if the length of the string is greater than
* OBJ_ENCODING_EMBSTR_SIZE_LIMIT. */
// 最后只能OBJ_ENCODING_RAW编码，但是最终再尝试压缩数据
trimStringObjectIfNeeded(o);
/* Return the original object. */
return o;
}从上面这段代码中，再次可以看出Redis对于内存的严格使用，OBJ_STRING类型的编码有三种：OBJ_ENCODING_RAW、OBJ_ENCODING_INT、OBJ_ENCODING_EMBSTR，这三种方式对于内存的需求是不一样的，OBJ_ENCODING_INT和OBJ_ENCODING_EMBSTR不需要额外的内存，OBJ_ENCODING_RAW需要一个void 指针的空间。
在tryObjectEncoding中，首先尝试编码为OBJ_ENCODING_INT，即如果value的长度<20并且可以转化为int类型，那么直接把void * ptr赋值为转化之后的整数值；然后如果value的长度不大，则编码为OBJ_ENCODING_EMBSTR，这样value的内存和robj的内存是连续的；最后才尝试OBJ_ENCODING_RAW编码，void ptr指针value的真实地址，此时还会调用trimStringObjectIfNeeded尽可能的压缩value生成的sds内存。
最后调用setGenericCommand处理：
void setGenericCommand(client *c, int flags, robj *key, robj *val, robj *expire, int unit, robj *ok_reply, robj *abort_reply) {
long long milliseconds = 0; /* initialized to avoid any harmness warning */
// 判断过期时间是否是整数
if (expire) {
if (getLongLongFromObjectOrReply(c, expire, &milliseconds, NULL) != C_OK)
return;
if (milliseconds <= 0) {
addReplyErrorFormat(c,"invalid expire time in %s",c->cmd->name);
return;
}
if (unit == UNIT_SECONDS) milliseconds *= 1000;
}
// 判断是否符合nx的要求
if ((flags & OBJ_SET_NX && lookupKeyWrite(c->db,key) != NULL) ||
(flags & OBJ_SET_XX && lookupKeyWrite(c->db,key) == NULL))
{
addReply(c, abort_reply ? abort_reply : shared.nullbulk);
return;
}
// 设置KV对
setKey(c->db,key,val);
server.dirty++;
// 如果有过期时间，则设置
if (expire) setExpire(c,c->db,key,mstime()+milliseconds);
notifyKeyspaceEvent(NOTIFY_STRING,"set",key,c->db->id);
if (expire) notifyKeyspaceEvent(NOTIFY_GENERIC,
"expire",key,c->db->id);
// 回复客户端
addReply(c, ok_reply ? ok_reply : shared.ok);
}lookupKeyWrite用来判断key是否在db中已经存在，与之对应的还有一个lookupKeyRead，两者都用来查找key，但是lookupKeyWrite表示查找key之后，可能会对key更新，所以会尝试对key进行过期时间过滤。
接下来向db中添加key和value：如果key存在则覆盖原来的value，否则插入KV对
void setKey(redisDb *db, robj *key, robj *val) {
if (lookupKeyWrite(db,key) == NULL) {
dbAdd(db,key,val);
} else {
dbOverwrite(db,key,val);
}
incrRefCount(val);
removeExpire(db,key);
signalModifiedKey(db,key);
}最后如果设置了过期时间，则向redisDb的expires中插入key对应的过期时间。
这里有关函数notifyKeyspaceEvent，用来实现key空间操作的通知，在后面文章中再详细介绍
get:
void getCommand(client *c) {
getGenericCommand(c);
}
int getGenericCommand(client *c) {
robj *o;
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk)) == NULL)
return C_OK;
if (o->type != OBJ_STRING) {
addReply(c,shared.wrongtypeerr);
return C_ERR;
} else {
addReplyBulk(c,o);
return C_OK;
}
}get命令比较简单，先查询，如果查到了，并且类型是字符串，则返回成功，否则返回失败。
列表(list)命令实现
与列表有关的命令实现都在t_list.c中，这里主要解析插入、删除、查找三类命令。
插入命令有：rpush、lpush、rpushx、lpushx、linsert、rpoplpush
void lpushCommand(client *c) {
// 头部插入
pushGenericCommand(c,LIST_HEAD);
}
void rpushCommand(client *c) {
// 尾部插入
pushGenericCommand(c,LIST_TAIL);
}
void pushGenericCommand(client *c, int where) {
int j, pushed = 0;
// 判断key是否存在
robj *lobj = lookupKeyWrite(c->db,c->argv[1]);
// 如果key存在，判断key的类型是不是OBJ_LIST
if (lobj && lobj->type != OBJ_LIST) {
addReply(c,shared.wrongtypeerr);
return;
}
for (j = 2; j < c->argc; j++) {
if (!lobj) {
// 如果key不存在，则创建
lobj = createQuicklistObject();
quicklistSetOptions(lobj->ptr, server.list_max_ziplist_size,
server.list_compress_depth);
dbAdd(c->db,c->argv[1],lobj);
}
// 最终调用quicklistPush向列表中插入元素
listTypePush(lobj,c->argv[j],where);
pushed++;
}
// 向用户返回列表总长度
addReplyLongLong(c, (lobj ? listTypeLength(lobj) : 0));
if (pushed) {
char *event = (where == LIST_HEAD) ? "lpush" : "rpush";
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_LIST,event,c->argv[1],c->db->id);
}
server.dirty += pushed;
}
void linsertCommand(client *c) {
int where;
robj *subject;
listTypeIterator *iter;
listTypeEntry entry;
int inserted = 0;
if (strcasecmp(c->argv[2]->ptr,"after") == 0) {
where = LIST_TAIL;
} else if (strcasecmp(c->argv[2]->ptr,"before") == 0) {
where = LIST_HEAD;
} else {
addReply(c,shared.syntaxerr);
return;
}
// 先查找，没有key或者key的类型不对，就返回错误
if ((subject = lookupKeyWriteOrReply(c,c->argv[1],shared.czero)) == NULL ||
checkType(c,subject,OBJ_LIST)) return;
/* Seek pivot from head to tail */
// 寻找要插入的位置，找到就插入
iter = listTypeInitIterator(subject,0,LIST_TAIL);
while (listTypeNext(iter,&entry)) {
if (listTypeEqual(&entry,c->argv[3])) {
listTypeInsert(&entry,c->argv[4],where);
inserted = 1;
break;
}
}
listTypeReleaseIterator(iter);
if (inserted) {
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_LIST,"linsert",
c->argv[1],c->db->id);
server.dirty++;
} else {
/* Notify client of a failed insert */
addReply(c,shared.cnegone);
return;
}
addReplyLongLong(c,listTypeLength(subject));
}删除命令有：rpop、lpop、brpoplpush、blpop、blpush、lrem、ltrim
void lpopCommand(client *c) {
// 头部删除
popGenericCommand(c,LIST_HEAD);
}
void rpopCommand(client *c) {
// 尾部删除
popGenericCommand(c,LIST_TAIL);
}
void popGenericCommand(client *c, int where) {
// 查找key并判断key类型
robj *o = lookupKeyWriteOrReply(c,c->argv[1],shared.nullbulk);
if (o == NULL || checkType(c,o,OBJ_LIST)) return;
robj *value = listTypePop(o,where);
if (value == NULL) {
// list中没有元素，则错误返回
addReply(c,shared.nullbulk);
} else {
char *event = (where == LIST_HEAD) ? "lpop" : "rpop";
addReplyBulk(c,value);
decrRefCount(value);
notifyKeyspaceEvent(NOTIFY_LIST,event,c->argv[1],c->db->id);
// 删除元素后，如果列表为空，则删除列表，释放内存
if (listTypeLength(o) == 0) {
notifyKeyspaceEvent(NOTIFY_GENERIC,"del",
c->argv[1],c->db->id);
dbDelete(c->db,c->argv[1]);
}
signalModifiedKey(c->db,c->argv[1]);
server.dirty++;
}
}查询命令有：lindex
void lindexCommand(client *c) {
// 查找key并判断key类型
robj *o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk);
if (o == NULL || checkType(c,o,OBJ_LIST)) return;
long index;
robj *value = NULL;
if ((getLongFromObjectOrReply(c, c->argv[2], &index, NULL) != C_OK))
return;
if (o->encoding == OBJ_ENCODING_QUICKLIST) {
quicklistEntry entry;
// 通过qucklist的api查找指定位置的元素
if (quicklistIndex(o->ptr, index, &entry)) {
if (entry.value) {
value = createStringObject((char*)entry.value,entry.sz);
} else {
value = createStringObjectFromLongLong(entry.longval);
}
addReplyBulk(c,value);
decrRefCount(value);
} else {
addReply(c,shared.nullbulk);
}
} else {
serverPanic("Unknown list encoding");
}
}哈希(hash)命令实现
hash命令的实现在t_hash.c中，hash的底层编码有两种OBJ_ENCODING_ZIPLIST、OBJ_ENCODING_HT，实现相对来说复杂点，这里看看hset、hget、hdel三个命令的实现。
hset:
void hsetCommand(client *c) {
int i, created = 0;
robj *o;
if ((c->argc % 2) == 1) {
addReplyError(c,"wrong number of arguments for HMSET");
return;
}
// 查找key，没有就新建
if ((o = hashTypeLookupWriteOrCreate(c,c->argv[1])) == NULL) return;
// 尝试转化hash底层的编码方式
hashTypeTryConversion(o,c->argv,2,c->argc-1);
// 逐一设置hash中对应field的value
for (i = 2; i < c->argc; i += 2)
created += !hashTypeSet(o,c->argv[i]->ptr,c->argv[i+1]->ptr,HASH_SET_COPY);
/* HMSET (deprecated) and HSET return value is different. */
char *cmdname = c->argv[0]->ptr;
if (cmdname[1] == 's' || cmdname[1] == 'S') {
/* HSET */
addReplyLongLong(c, created);
} else {
/* HMSET */
addReply(c, shared.ok);
}
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_HASH,"hset",c->argv[1],c->db->id);
server.dirty++;
}hashTypeTryConversion函数尝试进行底层编码转化，hash新建时，为了节省内存，底层编码方式为OBJ_ENCODING_ZIPLIST，随着内部KV的添加，在达到一定条件时，会转化为OBJ_ENCODING_HT，这个条件如下：1、filed所对应的value的字符串长度达到一定阈值；2、ziplist中元素个数达到一定阈值。
来看下编码转化的实现：
void hashTypeConvert(robj *o, int enc) {
if (o->encoding == OBJ_ENCODING_ZIPLIST) {
// 只有OBJ_ENCODING_ZIPLIST才能转化成OBJ_ENCODING_HT
hashTypeConvertZiplist(o, enc);
} else if (o->encoding == OBJ_ENCODING_HT) {
serverPanic("Not implemented");
} else {
serverPanic("Unknown hash encoding");
}
}
void hashTypeConvertZiplist(robj *o, int enc) {
serverAssert(o->encoding == OBJ_ENCODING_ZIPLIST);
if (enc == OBJ_ENCODING_ZIPLIST) {
/* Nothing to do... */
} else if (enc == OBJ_ENCODING_HT) {
hashTypeIterator *hi;
dict *dict;
int ret;
// 创建ziplist的迭代器
hi = hashTypeInitIterator(o);
// 创建编码方式为OBJ_ENCODING_HT的dict
dict = dictCreate(&hashDictType, NULL);
// 逐个KV迭代
while (hashTypeNext(hi) != C_ERR) {
sds key, value;
key = hashTypeCurrentObjectNewSds(hi,OBJ_HASH_KEY);
value = hashTypeCurrentObjectNewSds(hi,OBJ_HASH_VALUE);
// 将ziplist中的KV对添加到dict中
ret = dictAdd(dict, key, value);
if (ret != DICT_OK) {
serverLogHexDump(LL_WARNING,"ziplist with dup elements dump",
o->ptr,ziplistBlobLen(o->ptr));
serverPanic("Ziplist corruption detected");
}
}
hashTypeReleaseIterator(hi);
zfree(o->ptr);
// 最后更改编码方式，设置新的指针指向
o->encoding = OBJ_ENCODING_HT;
o->ptr = dict;
} else {
serverPanic("Unknown hash encoding");
}
}hashTypeSet函数用来向hash设置KV，也是根据编码类型做不同的操作，如果最初编码是OBJ_ENCODING_ZIPLIST，那么插入KV对之后，尝试更改底层编码方式
int hashTypeSet(robj *o, sds field, sds value, int flags) {
if (o->encoding == OBJ_ENCODING_ZIPLIST) {
...
/* Check if the ziplist needs to be converted to a hash table */
// 尝试更改底层编码
if (hashTypeLength(o) > server.hash_max_ziplist_entries)
hashTypeConvert(o, OBJ_ENCODING_HT);
} else if (o->encoding == OBJ_ENCODING_HT) {
}
}hget: 根据编码类型做响应的查找操作
void hgetCommand(client *c) {
robj *o;
if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk)) == NULL ||
checkType(c,o,OBJ_HASH)) return;
addHashFieldToReply(c, o, c->argv[2]->ptr);
}
static void addHashFieldToReply(client *c, robj *o, sds field) {
int ret;
if (o == NULL) {
addReply(c, shared.nullbulk);
return;
}
if (o->encoding == OBJ_ENCODING_ZIPLIST) {
...
} else if (o->encoding == OBJ_ENCODING_HT) {
...
} else {
serverPanic("Unknown hash encoding");
}
}hdel: 根据编码类型做响应的删除操作：
void hdelCommand(client *c) {
robj *o;
int j, deleted = 0, keyremoved = 0;
// 查找key，并判断key类型
if ((o = lookupKeyWriteOrReply(c,c->argv[1],shared.czero)) == NULL ||
checkType(c,o,OBJ_HASH)) return;
for (j = 2; j < c->argc; j++) {
// 根据编码类型做删除操作
if (hashTypeDelete(o,c->argv[j]->ptr)) {
deleted++;
if (hashTypeLength(o) == 0) {
dbDelete(c->db,c->argv[1]);
keyremoved = 1;
break;
}
}
}
if (deleted) {
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_HASH,"hdel",c->argv[1],c->db->id);
if (keyremoved)
notifyKeyspaceEvent(NOTIFY_GENERIC,"del",c->argv[1],
c->db->id);
server.dirty += deleted;
}
addReplyLongLong(c,deleted);
}集合(set)命令实现
set命令的实现在t_set.c中，set的底层编码方式有两种：OBJ_ENCODING_INTSET、OBJ_ENCODING_HT，其中OBJ_ENCODING_INTSET的底层实现是intset
set添加saddCommand：
void saddCommand(client *c) {
robj *set;
int j, added = 0;
// 查找key，没有则创建
set = lookupKeyWrite(c->db,c->argv[1]);
if (set == NULL) {
set = setTypeCreate(c->argv[2]->ptr);
dbAdd(c->db,c->argv[1],set);
} else {
if (set->type != OBJ_SET) {
addReply(c,shared.wrongtypeerr);
return;
}
}
// 插入元素
for (j = 2; j < c->argc; j++) {
if (setTypeAdd(set,c->argv[j]->ptr)) added++;
}
if (added) {
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_SET,"sadd",c->argv[1],c->db->id);
}
server.dirty += added;
addReplyLongLong(c,added);
}插入元素时，如果1、待插入的元素不能编码为整数；2、intset的元素个数超过阈值，就会将set的底层编码从OBJ_ENCODING_INTSET转化为OBJ_ENCODING_HT，下面是转化条件：
int setTypeAdd(robj *subject, sds value) {
long long llval;
if (subject->encoding == OBJ_ENCODING_HT) {
dict *ht = subject->ptr;
dictEntry *de = dictAddRaw(ht,value,NULL);
if (de) {
dictSetKey(ht,de,sdsdup(value));
dictSetVal(ht,de,NULL);
return 1;
}
} else if (subject->encoding == OBJ_ENCODING_INTSET) {
if (isSdsRepresentableAsLongLong(value,&llval) == C_OK) {
// value可以被编码为整数
uint8_t success = 0;
subject->ptr = intsetAdd(subject->ptr,llval,&success);
if (success) {
/* Convert to regular set when the intset contains
* too many entries. */
if (intsetLen(subject->ptr) > server.set_max_intset_entries)
// intset大小超过阈值
setTypeConvert(subject,OBJ_ENCODING_HT);
return 1;
}
} else {
/* Failed to get integer from object, convert to regular set. */
setTypeConvert(subject,OBJ_ENCODING_HT);
/* The set *was* an intset and this value is not integer
* encodable, so dictAdd should always work. */
serverAssert(dictAdd(subject->ptr,sdsdup(value),NULL) == DICT_OK);
return 1;
}
} else {
serverPanic("Unknown set encoding");
}
return 0;
}删除元素的过程也很简单，先查找key，在调用intset或者dict的api逐一删除元数：
void sremCommand(client *c) {
robj *set;
int j, deleted = 0, keyremoved = 0;
if ((set = lookupKeyWriteOrReply(c,c->argv[1],shared.czero)) == NULL ||
checkType(c,set,OBJ_SET)) return;
for (j = 2; j < c->argc; j++) {
if (setTypeRemove(set,c->argv[j]->ptr)) {
deleted++;
if (setTypeSize(set) == 0) {
dbDelete(c->db,c->argv[1]);
keyremoved = 1;
break;
}
}
}
if (deleted) {
signalModifiedKey(c->db,c->argv[1]);
notifyKeyspaceEvent(NOTIFY_SET,"srem",c->argv[1],c->db->id);
if (keyremoved)
notifyKeyspaceEvent(NOTIFY_GENERIC,"del",c->argv[1],
c->db->id);
server.dirty += deleted;
}
addReplyLongLong(c,deleted);
}有序集合（sorted set）命令
有序集合的实现都在t_zset.c中，sorted set的底层编码有OBJ_ENCODING_ZIPLIST、OBJ_ENCODING_SKIPLIST两种
zadd同样先查找key，不存在则创建，然后调用ziplist或者skiplist中的API逐一向key中添加元素，中间达到阈值时，转化底层编码方式
void zaddGenericCommand(client *c, int flags) {
...
/* Lookup the key and create the sorted set if does not exist. */
// 查找key，不存在则创建
zobj = lookupKeyWrite(c->db,key);
if (zobj == NULL) {
if (xx) goto reply_to_client; /* No key + XX option: nothing to do. */
if (server.zset_max_ziplist_entries == 0 ||
server.zset_max_ziplist_value < sdslen(c->argv[scoreidx+1]->ptr))
{
zobj = createZsetObject();
} else {
zobj = createZsetZiplistObject();
}
dbAdd(c->db,key,zobj);
} else {
if (zobj->type != OBJ_ZSET) {
addReply(c,shared.wrongtypeerr);
goto cleanup;
}
}
// 逐个插入元素
for (j = 0; j < elements; j++) {
double newscore;
score = scores[j];
int retflags = flags;
ele = c->argv[scoreidx+1+j*2]->ptr;
int retval = zsetAdd(zobj, score, ele, &retflags, &newscore);
if (retval == 0) {
addReplyError(c,nanerr);
goto cleanup;
}
if (retflags & ZADD_ADDED) added++;
if (retflags & ZADD_UPDATED) updated++;
if (!(retflags & ZADD_NOP)) processed++;
score = newscore;
}
server.dirty += (added+updated);
...
}zrem、zremrangebyscore、zremrangebyrank等删除命令也类似
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