# Don't load little bobby tables
sql = "SELECT * FROM user WHERE user_id = ?"
key = 'SQL:' . user_id . ':' . md5sum(sql)
# We check if the value is 'defined', since '0' or 'FALSE' # can be
# legitimate values!
if (defined result = memcli:get(key)) {
return result
} else {
handler = run_sql(sql, user_id)
# Often what you get back when executing SQL is a special handler
# object. You can't directly cache this. Stick to strings, arrays,
# and hashes/dictionaries/tables
rows_array = handler:turn_into_an_array
# Cache it for five minutes
memcli:set(key, rows_array, 5 * 60)
return rows_array
}
Key Usage Thinking about your keys can save you a lot of time and memory. Memcached is a hash, but it also remembers the full key internally. The longer your keys are, the more bytes memcached has to hash to look up your value, and the more memory it wastes storing a full copy of your key. On the other hand, it should be easy to figure out exactly where in your code a key came from. Otherwise many laborous hours of debugging wait for you. Avoid User Input It’s very easy to compromise memcached if you use arbitrary user input for keys. The ASCII protocol uses spaces and newlines. Ensure that neither show up your keys, live long and prosper. Binary protocol does not have this issue. Short Keys 64-bit UID’s are clever ways to identify a user, but suck when printed out. 18446744073709551616. 20 characters! Using base64 encoding, or even just hexadecimal, you can cut that down by quite a bit. With the binary protocol, it’s possible to store anything, so you can directly pack 4 bytes into the key. This makes it impossible to read back via the ASCII protocol, and you should have tools available to simply determine what a key is. Informative Keys key = ‘SQL’ . md5sum(“SELECT blah blah blah”) … might be clever, but if you’re looking at this key via tcpdump, strace, etc. You won’t have any clue where it’s coming from. In this particular example, you may put your SQL queries into an outside file with the md5sum next to them. Or, more simply, appending a unique query ID into the key. key = ‘SQL’ . query_id . ‘:’ . m5sum(“SELECT blah blah blah”)
On a fast machine with very high speed networking, memcached can easily handle 200,000+ requests per second. With heavy tuning or even faster hardware it can go many times that. Hitting it a few hundred times per second, even on a slow machine, usually isn’t cause for concern.
响应迅速，考虑网络抖动，OS，CPU的延迟后，很少有响应会超过1-2毫秒
On a good day memcached can serve requests in less than a millisecond. After accounting for outliers due to OS jitter, CPU scheduling, or network jitter, very few commands should take more than a millisecond or two to complete.
理论上不会有连接client限制
Since memcached uses an event based architecture, a high number of clients will not generally slow it down. Users have hundreds of thousands of connected clients, working just fine.
但是会有硬件上的限制
Each connected client uses some TCP memory. You can only connect as many clients as you have spare RAM
High connection churn requires OS tuning. You will run out of local ports, TIME_WAIT buckets, and similar. Do research on how to properly tune the TCP stack for your OS.
A ROWID is an identification tag unique for each row of an Oracle Database table. The ROWID can be thought of as a virtual column, containing the ID for each row.
The oracle.sql.ROWID class i
public class DeleteNode_O1_Time {
/**
* Q 60 在O(1)时间删除链表结点
* 给定链表的头指针和一个结点指针(!!)，在O(1)时间删除该结点
*
* Assume the list is:
* head->...->nodeToDelete->mNode->nNode->..
格式定义The format specifiers supported by the NSString formatting methods and CFString formatting functions follow the IEEE printf specification; the specifiers are summarized in Table 1. Note that you c
概念
AngularJS is a structural framework for dynamic web apps.
了解更多详情请见原文链接：http://www.gbtags.com/gb/share/5726.htm
Directive
扩展html，给html添加声明语句，以便实现自己的需求。对于页面中html元素以ng为前缀的属性名称，ng是angular的命名空间
