I'm new to Redis...
Can I remove a member from a sorted set if the member's score has not changed?
Note: I know that I can do the following:
WATCH my-set
... [do some other stuff] ...
MULTI
ZREM my-set my-member
EXEC
But I believe this will abort the transaction (i.e. not execute ZREM) if any member of the set has changed. I'm only interested in aborting the transaction if my-member score has changed.
Can I achieve this without using server-side Lua?
Thanks!
Related
I want to change the setting of max user limit of jitsi in one room, cause I saw there was notifyMaxUsersLimitReached in UI.js, so where should I set this value? In jicofo or videobridge? is it there: https://github.com/jitsi/jicofo/blob/master/src/main/java/org/jitsi/jicofo/JitsiMeetGlobalConfig.java#L60
or other place?
This value could be specified in the option org.jitsi.jicofo.MAX_SSRC_PER_USER
It could be set in /etc/jitsi/jicofo/config, in the variable JAVA_SYS_PROPS, something like :
JAVA_SYS_PROPS="-Dorg.jitsi.jicofo.MAX_SSRC_PER_USER=100 ...."
Suppose you have a Keen IO collection called "survey-completed" that contains events matching the following pattern:
keen.id: <unique autogenerated id>
keen.timestamp: <autogenerated overridable timestamp>
userId: <hex string for user>
surveyScore: <integer from 1 to 10>
...
How would you create a report of only the most up-to-date satisfaction score for each user that responded to one or more surveys within a given amount of time (such as one week)?
There isn't a really elegant way to make it happen, but for a given userId you could successfully return your the most up-to-date event create a count query with a group_by on [surveyScore, keen.timestamp] and an order_by on the keen.timestamp property. You will want to set limit=1 to select only the most recent surveyScore.
If you'd like to use an extraction, the most straight forward way would be to run an extraction with property_names set to ["userId","keen.timestamp","surveyScore"]. Once you receive the results you can then do some client-side post processing. This is probably the best way if you want to take a look at all of your userIds.
If you're interested in a given userId and want to use an extraction, you can run an extraction with a filter on the userId eq X, define the optional parameter latest set to latest=1. The latest property is an integer containing the number of most recent events to extract. Note: The use of latest will call upon the keen.created_at timestamp instead of keen.timestamp (https://keen.io/docs/api/#the-keen-object).
I'm crash coursing right now in redis, using 'the little redis book'.
What's not clear to me is how I can autogenerate key values.
So for example, the book uses this set statement:
set users:9001 '{"id":9001, "email":"leto#dune.gov"}'
How can i set things up so that the system keeps track of the next available id? In this case... 9002?
I know there is a INCR function... But I don't know how to incorporate both of these functions together.
So for example, let's say i do this using the redis-cli:
set mykey 1
set users:mykey '{"id":mykey, "email":"leto#dune.gov"}'
This works on the command line, but I need a way to do this programmatically. I'm thinking I would:
get mykey
INCR mykey
set users:mykey ....
Does this seem right? is there another way to do this? Also how do I programmatically using phpredis?
Thanks.
Yes, that is the right way to do it. But a small change in your approach,
When you do INCR you will get a incremented value returned by redis. you can use it directly in the next command. So it is simply,
var counter = INCR key
set users:counter . . .
So here you start from the index 1. ie, users:1, users:2 and so on.
Hope this is clear.
I was looking at another question in stackoverflow regarding auto increment fields in orientdb, where one of the answers was to create our own vertex with counter field.
However, when I'm trying to execute the following code (both java api and console script batch), It is not working.
Do note however that the id is returned good (did some debug attempts, returning the id variable only), and the vertex is created.
However, the vertex id is always null (unless I set it explicit, that is).
The script:
script sql
LET id = UPDATE CCounter INCREMENT value=1 RETURN AFTER $current WHERE name='session'
LET csession = CREATE VERTEX CDate SET id=$id.result, meet_date='2015-01-01 15:23:00'
end
I tried playing around with $id and $current , but nothing seems to work.
Currently I am doing it in a 2-transaction mode; one to get the id, and another to create the vertex. I really hope there is a better way though.
P.S.
I am using version 2.0-M2
You should execute
LET csession = CREATE VERTEX CDate SET id=$id.value, meet_date='2015-01-01 15:23:00'
Note the $id.value in place of $id.result.
As stated in a comment to Lvca, the answer was:
(1) Change the field name. Id seems to be reserved (ish). It's probably possible to still bypass it and use a field named 'id', but I didn't want to mess around with it.
(2) From some reason, the result was a collection (shown as '[id]'). It took me some time to figure it out, but I just had to choose the first value from it.
(3) Also, there are 2 'values' here. One of the field ($current.value), and the second one(not sure where it's coming from).
Final solution that works:
script sql
LET id = UPDATE CCounter INCREMENT value = 1 RETURN AFTER $current.value WHERE name='session'
LET csession = CREATE VERTEX CDate SET data_id=$id[0].value, meet_date='2015-01-01 15:23:00'
end
I want to match my user to a different user in his/her community every day. Currently, I use code like this:
#matched_user = User.near(#user).order("RANDOM()").first
But I want to have a different #matched_user on a daily basis. I haven't been able to find anything in Stack or in the APIs that has given me insight on how to do it. I feel it should be simpler than having to resort to a rake task with cron. (I'm on postgres.)
Whenever I find myself hankering for shared 'memory' or transient state, I think to myself "this is what (distributed) caches were invented for".
#matched_user = Rails.cache.fetch(#user.cache_key + '/daily_match', expires_in: 1.day) {
User.near(#user).order("RANDOM()").first
}
NOTE: While specifying a TTL for cache entry tells Rails/the cache system to try and keep that value for the given timeframe, there's NO guarantee that it will. In particular, a cache that aggressively tries to reclaim memory may expire an entry well before its desired expires_in time.
For this particular use case, it shouldn't be a big deal but in cases where the business/domain logic demands periodically generated values that are durable then you really have to factor that into your database.
How about using PostgreSQL's SETSEED function? I used the date to seed so that every day the seed will change, but within a day, the seed will be consistent.:
User.connection.execute "SELECT SETSEED(#{Date.today.strftime("%y%d%m").to_i/1000000.0})"
#matched_user = User.near(#user).order("RANDOM()").first
You may want to seed a random value after using this so that any future calls to random aren't biased:
random = User.connection.execute("SELECT RANDOM()").to_a.first["random"]
# Same code as above:
User.connection.execute "SELECT SETSEED(#{Date.today.strftime("%y%d%m").to_i/1000000.0})"
#matched_user = User.near(#user).order("RANDOM()").first
# Use random value before seed to make new seed:
User.connection.execute "SELECT SETSEED(#{random})"
I have split these steps in different sections just for readability. you can optimise query later.
1) Find all user records till today morning. so that the count will freeze.
usrs_till_today_morning = User.where("created_at <?", DateTime.now.in_time_zone(Time.zone).beginning_of_day)
2) Pluck all ID's
user_ids = usr_till_today_morning.pluck(:id)
3) Today date it will be a range (1..30) but will remain constant throughout the day.
day_today = Time.now.day
4) Select the same ID for the day
todays_user_id = user_ids[day_today % user_ids.count]
#matched_user = User.find(todays_user_id)
So it will give you random user records by maintaining same record throughout the day!!