El nucleo de la programacion asincrona son los objetos Task y Task<T>. Ambos son compatibles con las palabras clave async y await.

Primero hay que identificar si el codigo se usa para trabajos enlazados a I/O o si estos son CPU intensivos.

• Si el codigo espera algo como una BBDD o una response de un servidor, es codigo I/O. En este caso hay que usar async y await
• Si el codigo realiza un calculo costoso, es CPU intensivo. Use await para esperar una operacion que se ha comenzado en background con Task.run

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i18n is just a nomenclature for Internationalization. i18n involves, among other things, the ability to display translated content. It prepares a digital product for localization by for example, separate the content into strings so they are ready to be translated and delivered.

The same goes for L10n. This is a nomenclature for Localization. L10n involves translating content, adapting graphics and finalizing the producto for each regional market.

Reference(s)

https://www.oneskyapp.com/blog/i18n-need-to-know-internationalization/

Indexes are a basic structure type that apply to one or multiple columns in order to improve performance and speed up queries that: filter, sort or join data for a table.

this may improve performance for a query that uses last_name in a WHERE clause or an ORDER BY

CREATE INDEX idx_last_name ON employees (last_name);

you can also create composite indexes

CREATE INDEX idx_composite ON employees (last_name, first_name)

and also composite index for only active employees

CREATE INDEX idx_active_employees ON employees (status) WHERE status = 'active';

When to use indexes

Frequent filters WHERE - if you usually filter by a specific column (last_name for example), an index should improve performance.

JOIN for big tables - when you use JOIN with big tables through PKs or FKs.

ORDER BY or GROUP BY - queries that search for / group by a specific column also benefit from indexes.

Best practices

Don’t create indexes in every column. This slows things down on insert, delete or update operations.

Index are best used for big domain fields such as ids, names, surnames. Don’t use them for male/female (or boolean) fields.

Keep indexes optimized: operations where you mass update or mass delete items in your tables may fragment your indexes. You may need to periodically check them and REINDEX them.

ALWAYS MEASURE PERFORMANCE TIME before and after the creation of that index. If your index doesn’t improve performance, remove it as it causes overhead.

Reference(s)

https://stackoverflow.com/questions/7744038/decision-when-to-create-index-on-table-column-in-database
https://stackoverflow.com/questions/52444912/how-to-find-out-fragmented-indexes-and-defragment-them-in-postgresql
https://chatgpt.com/

UNION

The union sentence is used to accumulate results for two SELECT sentences.

SELECT column1, column2 FROM table1
UNION
SELECT column1, column2 FROM table2

We have the following tables

company1

company2

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Find an exact match of a nested field (note that .keyword has to be added to string fields)

{
  "query": {
    "bool": {
      "must": [
        {
          "term": {
            "metadata.title.keyword": "File test.pdf"
          }
        }
      ]
    }
  },
  "size": 200
}

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These are my posts with knowledge about Azure services and usage.

Azure CosmosDB
Azure CosmosDB query examples

Azure Cloud Functions
Azure Functions - Introduction

(for this post some formulas and menu names are in spanish as my excel and computer are in spanish and excel formulas depend on this).

The formula is:

=AGREGAR(3;3;J:J)-1

The first two parameters are for the function itself. The important one is J:J which marks the column to count. What’s important here is this is not going to count filtered items in tables.

Watch out with headers! If you have headers in your table, add -1 to your formula.

(for this post some formulas and menu names are in spanish as my excel and computer are in spanish and excel formulas depend on this).

Here is how to find and mark differences in unequal, really long lists or tables in Excel. For my example, one list is a partial list from other. Some items are missing and you’ve to find which ones are.

This is the full list.

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Authentication process of verifying an identity. We confirm they’re who they say they are. (username & pwd).

Authorization process of verifying what someone is allowed to do. (Permissions and access control).

Past solutions

From worst one to best one and the problems they originate:

Credential Sharing

The worst one. An App is not able to differentiate between real user access and programmatical access.
Permissions are typically too broad. It also the ability to access more content than it should.

Cookie

We could redirect the user off to the API where they could enter their credentials and get a cookie. This allows an app to access the API.

Dangerous because CSRF attacks. We’ve authorised the whole browser and not the app.

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How to solve the problem “Low disk space on ‘Filesystem root’. The volume has only xMB disk space remaining” when you completely fill a virtual disk in VirtualBox.

(You have to delete all your snapshots first)

Open a cmd terminal and run the following command:

"c:\Program Files\Oracle\VirtualBox\VBoxManage.exe" modifymedium  
"c:\Users\mario\VirtualBox VMs\Ubuntu OTAN\Ubuntu OTAN.vdi" --resize 30000

The first path is an executable included with VirtualBox.
The second one is where your VDI actually is. --resize takes the size in MBs.

Open gpartitioner and resize it.

JMeter is a testing tool to simulate thousands of users for web testing purposes. It uses Java Threads for this.

1. JMeter
2. JMeter performance testing