I want to use redis to get value by key ,but the key is another key's value.like:
set name "david"
set david femal
i get david from the key->name,and the value as the second object's key,like
get (get name)
i hope the result is "femal",
how should i do?besides java client can support it .
Related
In hyperledger-fabric node js sdk.
Is there any possibility to search an asset with partial id?
for example my id is 'abc123'.
I can search with bc12 or abc or 123..and get the matching results.
Using stub.GetStateByRange(startKey, endKey) it is possible to retrieve results on a partial key, if they key has a specific form.
For eg.
the following keys could be used to successfully with a range query in the chaincode to retrieve a list of results, to match key abc123
a
ab
abc
abc1
abc12
abc123
However, a key without the same initial characters will not work. Eg. bc12 or 123.
The below function documentation gives a good idea of how the GetStateByRange function can be used.
// GetStateByRange returns a range iterator over a set of keys in the
// ledger. The iterator can be used to iterate over all keys
// between the startKey (inclusive) and endKey (exclusive).
// However, if the number of keys between startKey and endKey is greater than the
// totalQueryLimit (defined in core.yaml), this iterator cannot be used
// to fetch all keys (results will be capped by the totalQueryLimit).
// The keys are returned by the iterator in lexical order. Note
// that startKey and endKey can be empty string, which implies unbounded range
// query on start or end.
// Call Close() on the returned StateQueryIteratorInterface object when done.
// The query is re-executed during validation phase to ensure result set
// has not changed since transaction endorsement (phantom reads detected).
GetStateByRange(startKey, endKey string) (StateQueryIteratorInterface, error)
The answer by Clyde is the correct one to your question.
But, if you intend to perform complex queries in your code and you are in a position to refactor your data modelling, maybe you can set the information you must filter in some field inside your model (instead of or in addition to the ID itself) and perform rich queries against that field.
To do this, you must enable CouchDB as the state DB in your peers if haven't done it yet. Then you can query the DB and perform rich queries against your model fields.
Of course, this is not the answer to your question, but it may fit better to your use case if you are in a position to perform this kind of changes.
Whenever we save data to the database, there is always a corresponding ID which we use to fetch the data from that specific column.
sql_con.execute("SELECT FROM DBNAME WHERE ID = ?", id)
The above code only allows us to fetch data based from the ID. The problem is that the above code only accepts 1 supplied binding. In my database, I used sets of strings as the ID for each column, which means that the binding of my IDs are more than 1. And, those sets of strings have different bindings (or character count).
How do I modify the code in above, so I could input strings as my ID, preventing it from receiving the specific error:
sqlite3.ProgrammingError: Incorrect number of bindings supplied. The current statement uses 1, and there are 8 supplied.
Thank you in advance. I use Python 3.xx and in-built module sqlite3. Database is in .db file format and is a disk-based database.
I found the answer for my own question, by asking someone else.
For you to resolve this problem with the bindings of the input, just simply convert the parameter into a tuple.
OLD CODE:
sql_con.execute("SELECT FROM DBNAME WHERE ID = ?", id)
INTO THIS...
NEW CODE:
sql_con.execute("SELECT * FROM DBNAME WHERE ID = ?", (id,))
Hope it helps.
Is it possible to insert a new document into a Couchbase bucket without specifying the document's ID? I would like use Couchbase's Java SDK create a document and have Couchbase determine the document's UUID with Groovy code similar to the following:
import com.couchbase.client.java.CouchbaseCluster
import com.couchbase.client.java.Cluster
import com.couchbase.client.java.Bucket
import com.couchbase.client.java.document.JsonDocument
// Connect to localhost
CouchbaseCluster myCluster = CouchbaseCluster.create()
// Connect to a specific bucket
Bucket myBucket = myCluster.openBucket("default")
// Build the document
JsonObject person = JsonObject.empty()
.put("firstname", "Stephen")
.put("lastname", "Curry")
.put("twitterHandle", "#StephenCurry30")
.put("title", "First Unanimous NBA MVP)
// Create the document
JsonDocument stored = myBucket.upsert(JsonDocument.create(person));
No, Couchbase documents have to have a key, that's the whole point of a key-value store, after all. However, if you don't care what the key is, for example, because you retrieve documents through queries rather than by key, you can just use a uuid or any other unique value when creating the document.
It seems there is no way to have Couchbase generate the document IDs for me. At the suggestion of another developer, I am using UUID.randomUUID() to generate the document IDs in my application. The approach is working well for me so far.
Reference: https://forums.couchbase.com/t/create-a-couchbase-document-without-specifying-an-id/8243/4
As you already found out, generating a UUID is one approach.
If you want to generate a more meaningful ID, for instance a "foo" prefix followed by a sequence number, you can make use of atomic counters in Couchbase.
The atomic counter is a document that contains a long, on which the SDK relies to guarantee a unique, incremented value each time you call bucket.counter("counterKey", 1, 2). This code would take the value of the counter document "counterKey", increment it by 1 atomically and return the incremented value. If the counter doesn't exist, it is created with the initial value 2, which is the value returned.
This is not automatic, but a Couchbase way of creating sequences / IDs.
I am trying to access session data from node.js that is stored in redis.
In the redis-cli I ran Keys * and returned
1) "sess:ZRhBJSVLjbNMc-qJptjiSjp8lQhXGGBb"
2) "sess:6p1EcGvJukTT26h88NqoTGdz2R4zr_7k"
If I then run GET I get back what looks like a hash
redis 127.0.0.1:6379> GET sess:ZRhBJSVLjbNMc-qJptjiSjp8lQhXGGBb
"{cookie:{originalMaxAge:null,expires:null,httpOnly:true,path:/},userKey:a92ca307-b315-44bc-aadf-da838d063c78,
authenticated:true,clientKey:1ccb5308-2a7e-4f49-bcdf-b2379de44541}"
If I try to get the value in userKey using
hget sess:oq6RW1zP7sfcZZc4wb1RHbti390FxL7- userKey
it returns
ERR Operation against a key holding the wrong kind of value
so I ran a TYPE check and found that it's not a hash but a string. I am a bit confused now as the whole thing looks like a hash and I cannot figure out how to return the values that I need as just calling get returns the whole thing.
Is there some other command I need to use to get the values?
Thanks
If you can GET aganist the key then it is not a hash because you would get ERR Operation against a key holding the wrong kind of value. And it was confirmed by yourserlf doing HGET and getting the error.
Probably that keys looks like a hash because (it is a hash but not redis hash datatype) it is the unique token that was issued to user in his session cookie in client. When user send this cookie to the server in every request the server can retrieve session info from redis using the cookie value as redis key.
The value is a string in JSON format. You have to retrieve the whole value and parse it; ussing JSON.parse in node.js could do the job. Once the value is parsed you have a JavaScript object which attributes can be access in standard way:
var sessionData = JSON.parse(JSONString);
console.log(sessionData.userKey)
It's a string
You can't get some session value directly, because it's serialized to some format(in this case, JSON)
If the session is written by node.js, you should use the same API to read.
If the session is written by other system, and you must parse it with node, you should just GET it, and json parse it（JSON.parse）
I have a Node.js application with stores posts written by authors in a Redis database. The post is given a unique ID (the variable messageId), and two values are given: the message and the author. The first part of the code looks like so:
redisClient.hmset(messageId, "message", req.body.message, "author", req.body.author);
So far, so good. What I want to do is be able to retrieve the value of a specific key. I know I can use hgetall() to get all the keys and values for messageId, and I know I can use hkeys to get all the keys for messageId. If I know there will be a key called "message", how can I retrieve the value from message A) from the Redis client, and B) through Node.js?
NOTE: I have seen this: Redis + Node.js - how do I retrieve the values. It does not tell me what I need.
There is hget to retrieve a single value, and hmget to retrieve multiple values.
See Redis commands for hash. The node.js client should support them all.
Something like:
redisClient.hget(messageId, "message");
redisClient.hmget(messageId, ["message", "author"]);