HSET used to be able to set only one key-value pair. And if you needed to set several at once, you would have to use HMSET (M for multi). That was changed a few years ago, to allow both commands to accept multiple pairs. And now HMSET is redundant.

From [official documentation](https://redis.io/commands/hmset):

&gt; As per Redis 4.0.0, HMSET is considered deprecated. Please use HSET in new code.



**[HSET key field value][1]:** 

Sets field in the hash stored at key to value. If key does not exist, a new key holding a hash is created. If field already exists in the hash, it is overwritten.


**[HMSET key field value \[field value ...\]][2]** 

Sets the specified fields to their respective values in the hash stored at key. This command overwrites any existing fields in the hash. If key does not exist, a new key holding a hash is created.


For more redis commands information, [click here][3].


  [1]: http://redis.io/commands/hset
  [2]: http://redis.io/commands/hmset
  [3]: http://redis.io/commands

The only difference between the commands [`HSET`](https://redis.io/commands/hset) and [`HMSET`](https://redis.io/commands/hmset) is the **return value** of the commands. 

HSET return value (Integer reply): 

 - `#` if the field is a new field in the hash and value was set. (where `#` is the number of new fields created )
 - 0 if the field already exists in the hash and the value was updated.

HMSET returns a simple string as a reply.



How large is Scala&#39;s thread pool for futures?

My Scala application makes many millions of `future {}`s and I wonder if there is anything I can do to optimize them by configuring a thread pool.

Thank you.

How to configure a fine tuned thread pool for futures?

How to combine `rotateX(50deg) rotateY(20deg) rotateZ(15deg)` in shorthand `rotate3d()`?

rotate3d shorthand

In my application im using redis database.I have gone through their documentation but i couldn&#39;t find the difference between HSET and HMSET.

What is the difference between HSET and HMSET method in redis database

<p>In my application im using redis database.I have gone through their documentation but i couldn't find the difference between HSET and HMSET.</p>


I have a database table called &#39;**tbl_transaction**&#39; with the following definition:
    
    id INT(11) Primary Key
    action_type ENUM(&#39;Expense&#39;, &#39;Income&#39;)
    action_heading VARCHAR (255)
    action_amount FLOAT

I would like to generate two columns: `Income Amt` and `Expense Amt`.

Is it possible to populate the columns conditionally, using only a SQL Query, such that the output appears in the correct column, depending on whether it is an Expense item or an Income item?

For example:
    
    ID        Heading         Income Amt       Expense Amt
    1         ABC             1000             -
    2         XYZ             -                2000


I&#39;m using MySQL as the database. I&#39;m trying to use the CASE statement to accomplish this. 

Cheers!

Case statement in MySQL

I need to perform UPSERT / INSERT OR UPDATE against a SQLite Database.

There is the command INSERT OR REPLACE which in many cases can be useful. But if you want to keep your id&#39;s with autoincrement in place because of foreign keys, it does not work since it deletes the row, creates a new one and consequently this new row has a new ID.

This would be the table:

players - (primary key on id, user_name unique)


    |  id   | user_name |  age   |
    ------------------------------
    |  1982 |   johnny  |  23    |
    |  1983 |   steven  |  29    |
    |  1984 |   pepee   |  40    |




SQLite UPSERT / UPDATE OR INSERT

I want an SQL statement to get the row with a minimum value. 


Consider this table:

    id  game   point
    1    x      5
    1    z      4
    2    y      6
    3    x      2
    3    y      5
    3    z      8

How do I select the ids that have the minimum value in the `point` column, grouped by game?  Like the following:

    id  game   point    
    1    z      4
    2    y      5
    3    x      2   


SQL query to select distinct row with minimum value

The problem Im facing while trying to connect to database for mysql. I have also given the database settings that i have used.


     Traceback (most recent call last):
     File &quot;manage.py&quot;, line 10, in &lt;module&gt;
     execute_from_command_line(sys.argv)
     File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/core/management/__init__.py&quot;, line 453, in execute_from_command_line
    utility.execute()
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/core/management/__init__.py&quot;, line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/core/management/__init__.py&quot;, line 272, in fetch_command
    klass = load_command_class(app_name, subcommand)
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/core/management/__init__.py&quot;, line 77, in load_command_class
    module = import_module(&#39;%s.management.commands.%s&#39; % (app_name, name))
    File &quot;/home/arundhati/Desktop/test/testprac/local/lib/python2.7/site-packages/django/utils/importlib.py&quot;, line 35, in import_module
    __import__(name)
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/core/management/commands/syncdb.py&quot;, line 8, in &lt;module&gt;
    from django.core.management.sql import custom_sql_for_model, emit_post_sync_signal
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/core/management/sql.py&quot;, line 9, in &lt;module&gt;
    from django.db import models
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/db/__init__.py&quot;, line 40, in &lt;module&gt;
    backend = load_backend(connection.settings_dict[&#39;ENGINE&#39;])
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/db/__init__.py&quot;, line 34, in __getattr__
    return getattr(connections[DEFAULT_DB_ALIAS], item)
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/db/utils.py&quot;, line 93, in __getitem__
    backend = load_backend(db[&#39;ENGINE&#39;])
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/db/utils.py&quot;, line 27, in load_backend
    return import_module(&#39;.base&#39;, backend_name)
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/utils/importlib.py&quot;, line 35, in import_module
    __import__(name)
    File &quot;/home/ar/Desktop/test/testprac/local/lib/python2.7/site-packages/django/db/backends/mysql/base.py&quot;, line 17, in &lt;module&gt;
    raise ImproperlyConfigured(&quot;Error loading MySQLdb module: %s&quot; % e)
    django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb

Databse Settings::
         
    DATABASES = {
        &#39;default&#39;: {
            &#39;ENGINE&#39;: &#39;django.db.backends.mysql&#39;, # Add &#39;postgresql_psycopg2&#39;, &#39;mysql&#39;, &#39;sqlite3&#39; or &#39;oracle&#39;.
            &#39;NAME&#39;: &#39;ar_test_db&#39;,                      # Or path to database file if using 
            # The following settings are not used with sqlite3:
            &#39;USER&#39;: &#39;&#39;,
            &#39;PASSWORD&#39;: &#39;&#39;,
            &#39;HOST&#39;: &#39;&#39;,                      # Empty for localhost through domain sockets or   &#39;127.0.0.1&#39; for localhost through TCP.
            &#39;PORT&#39;: &#39;&#39;,                      # Set to empty string for default.
        }
    }

Thanks a lot for the help !!

django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named MySQLdb

I am implementing the following model for storing user related data in my table - I have 2 columns - `uid` (primary key) and a `meta` column which stores other data about the user in JSON format.  

     uid   | meta
    --------------------------------------------------
     1     | {name:[&#39;foo&#39;], 
           |  emailid:[&#39;foo@bar.com&#39;,&#39;bar@foo.com&#39;]}
    --------------------------------------------------
     2     | {name:[&#39;sann&#39;], 
           |  emailid:[&#39;sann@bar.com&#39;,&#39;sann@foo.com&#39;]}
    --------------------------------------------------

Is this a better way (performance-wise, design-wise) than the one-column-per-property model, where the table will have many columns  like `uid`, `name`, `emailid`. 

What I like about the first model is, you can add as many fields as possible there is no limitation. 

Also, I was wondering, now that I have implemented the first model. How do I perform a query on it, like, I want to fetch all the users who have name like &#39;foo&#39;?

**Question** - Which is the better way to store user related data (keeping in mind that number of fields is not fixed) in database using - JSON or column-per-field? Also, if the first model is implemented, how to query database as described above? Should I use both the models, by storing all the data which may be searched by a query in a separate row and the other data in JSON (is a different row)? 

-----------------------------------

Update
--

Since there won&#39;t be too many columns on which I need to perform search, is it wise to use both the models? Key-per-column for the data I need to search and JSON for others (in the same MySQL database)?

Storing JSON in database vs. having a new column for each key

In the redis.conf the normal setting is
    
bind 127.0.0.1
    
I want redis to listen to another ip too (say my local development address)
    
I tried 
    
bind 127.0.0.1, 123.33.xx.xx

but this does not work. I cannot find any relevant in the document or by googling. Hope someone can help.


Redis bind to more than one IP

So, I&#39;ve come to a place where I wanted to segment the data I store in redis into separate databases as I sometimes need to make use of the keys command on one specific kind of data, and wanted to separate it to make that faster.

If I segment into multiple databases, everything is still single threaded, and I still only get to use one core. If I just launch another instance of Redis on the same box, I get to use an extra core. On top of that, I can&#39;t name Redis databases, or give them any sort of more logical identifier. So, with all of that said, why/when would I ever want to use multiple Redis databases instead of just spinning up an extra instance of Redis for each extra database I want? And relatedly, why doesn&#39;t Redis try to utilize an extra core for each extra database I add? What&#39;s the advantage of being single threaded across databases?

What&#39;s the Point of Multiple Redis Databases?

Have Redis setup with ruby on ubuntu server, but can&#39;t figure out how to access its log file. Tutorial says it should be here:

    /var/log/redis_6379.log

But can&#39;t even find the /var/ folder

How to access Redis log file

I want to store a JSON payload into redis. There&#39;s really 2 ways I can do this:

1. One using a simple string keys and values.  
key:user, value:payload (the entire JSON blob which can be 100-200 KB)

    `SET user:1 payload`

2. Using hashes


   `HSET user:1 username &quot;someone&quot;  
    HSET user:1 location &quot;NY&quot;  
    HSET user:1 bio &quot;STRING WITH OVER 100 lines&quot;`


Keep in mind that if I use a hash, the value length isn&#39;t predictable. They&#39;re not all short such as the bio example above.

Which is more memory efficient? Using string keys and values, or using a hash?


Redis strings vs Redis hashes to represent JSON: efficiency?

I need to expire all keys in redis hash, which are older than 1 month.


Content Type	Original Author	Original Content on Stackoverflow
Question	sachin	View Question on Stackoverflow
Solution 1 - Database	Sergio Tulentsev	View Answer on Stackoverflow
Solution 2 - Database	Hrishikesh Mishra	View Answer on Stackoverflow
Solution 3 - Database	Gunasekar	View Answer on Stackoverflow

What is the difference between HSET and HMSET method in redis database

Database Problem Overview

Database Solutions

Solution 1 - Database

Solution 2 - Database

Solution 3 - Database

rotate3d shorthand

How to configure a fine tuned thread pool for futures?

Attributions