1. 设置命令
首先,redis定义了5个宏来确定当前设置的一些属性,具体如下
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#define OBJ_SET_NO_FLAGS 0
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#define OBJ_SET_NX (1<<0) /* Set if key not exists. */
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#define OBJ_SET_XX (1<<1) /* Set if key exists. */
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#define OBJ_SET_EX (1<<2) /* Set if time in seconds is given */
- #define OBJ_SET_PX (1<<3) /* Set if time in ms in given */
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/* SET key value [NX] [XX] [EX <seconds>] [PX <milliseconds>] */
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void setCommand(client *c) {
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int j;
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robj *expire = NULL;
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int unit = UNIT_SECONDS;
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int flags = OBJ_SET_NO_FLAGS;
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for (j = 3; j < c->argc; j++) {
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char *a = c->argv[j]->ptr;
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robj *next = (j == c->argc-1) ? NULL : c->argv[j+1];
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if ((a[0] == 'n' || a[0] == 'N') &&
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(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
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!(flags & OBJ_SET_XX))
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{
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flags |= OBJ_SET_NX;
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} else if ((a[0] == 'x' || a[0] == 'X') &&
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(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
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!(flags & OBJ_SET_NX))
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{
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flags |= OBJ_SET_XX;
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} else if ((a[0] == 'e' || a[0] == 'E') &&
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(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
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!(flags & OBJ_SET_PX) && next)
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{
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flags |= OBJ_SET_EX;
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unit = UNIT_SECONDS;
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expire = next;
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j++;
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} else if ((a[0] == 'p' || a[0] == 'P') &&
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(a[1] == 'x' || a[1] == 'X') && a[2] == '\0' &&
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!(flags & OBJ_SET_EX) && next)
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{
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flags |= OBJ_SET_PX;
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unit = UNIT_MILLISECONDS;
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expire = next;
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j++;
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} else {
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addReply(c,shared.syntaxerr);
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return;
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}
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}
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c->argv[2] = tryObjectEncoding(c->argv[2]);
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setGenericCommand(c,flags,c->argv[1],c->argv[2],expire,unit,NULL,NULL);
- }
这个就是整个set命令当中的重头戏,其余的所有set操作,在确定一些其他的参数后,都会调用这个函数,具体代码如下:
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void setGenericCommand(client *c, int flags, robj *key, robj *val, robj *expire, int unit, robj *ok_reply, robj *abort_reply) {
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long long milliseconds = 0; /* initialized to avoid any harmness warning */
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if (expire) {
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if (getLongLongFromObjectOrReply(c, expire, &milliseconds, NULL) != C_OK)
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return;
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if (milliseconds <= 0) {
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addReplyErrorFormat(c,"invalid expire time in %s",c->cmd->name);
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return;
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}
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if (unit == UNIT_SECONDS) milliseconds *= 1000;
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}
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if ((flags & OBJ_SET_NX && lookupKeyWrite(c->db,key) != NULL) ||
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(flags & OBJ_SET_XX && lookupKeyWrite(c->db,key) == NULL))
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{
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addReply(c, abort_reply ? abort_reply : shared.nullbulk);
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return;
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}
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setKey(c->db,key,val);
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server.dirty++;
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if (expire) setExpire(c,c->db,key,mstime()+milliseconds);
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notifyKeyspaceEvent(NOTIFY_STRING,"set",key,c->db->id);
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if (expire) notifyKeyspaceEvent(NOTIFY_GENERIC,
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"expire",key,c->db->id);
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addReply(c, ok_reply ? ok_reply : shared.ok);
- }
这里需要注意的一点是:每次调用set命令时,redis都会先调用tryObjectEncoding这个函数来尽量将值的编码类型转换为占用存储空间较小的那一个,之后才会调用setGenericCommand函数进行实际操作~~
get操作就相对没那么复杂,只需要调用底层的查找就行了
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int getGenericCommand(client *c) {
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robj *o;
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if ((o = lookupKeyReadOrReply(c,c->argv[1],shared.nullbulk)) == NULL)
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return C_OK;
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if (o->type != OBJ_STRING) {
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addReply(c,shared.wrongtypeerr);
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return C_ERR;
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} else {
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addReplyBulk(c,o);
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return C_OK;
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}
- }