Introduction

Since I installed Redash in my local environment the other day, this time I will put the data in the database and execute the query with Redash. Please see here for installing Redash.

environment

I'm using a MacBook Air. The OS etc. are as follows.

$sw_vers
ProductName:	Mac OS X
ProductVersion:	10.13.6
BuildVersion:	17G14033

$python --version
Python 3.7.3

$docker --version
Docker version 20.10.0, build 7287ab3

It is assumed that Redash is running.

$docker container ls
CONTAINER ID   IMAGE                 COMMAND                  CREATED          STATUS          PORTS                                            NAMES
caa3348d587a   redash_scheduler      "/app/bin/docker-ent…"   43 minutes ago   Up 42 minutes   5000/tcp                                         redash_scheduler_1
00e34fe2ef97   redash_worker         "/app/bin/docker-ent…"   43 minutes ago   Up 42 minutes   5000/tcp                                         redash_worker_1
0f60c28cecbd   redash_server         "/app/bin/docker-ent…"   43 minutes ago   Up 43 minutes   0.0.0.0:5000->5000/tcp, 0.0.0.0:5678->5678/tcp   redash_server_1
518d2c7aad0d   postgres:9.5-alpine   "docker-entrypoint.s…"   43 minutes ago   Up 43 minutes   0.0.0.0:15432->5432/tcp                          redash_postgres_1
c1e85b4cfa69   redis:3-alpine        "docker-entrypoint.s…"   27 hours ago     Up 27 hours     6379/tcp                                         redash_redis_1
d32426258263   djfarrelly/maildev    "bin/maildev --web 8…"   27 hours ago     Up 27 hours     25/tcp, 0.0.0.0:1080->80/tcp                     redash_email_1

Data preparation

The data uses the easily available scikit-learn Boston dataset. Boston home price data, 506 rows and 14 columns. The data items are described in detail in here, so I will omit the explanation.

First of all, I will take this data from scikit-learn and dump it to a csv file. Run the python code for that.

`data.py`


import pandas as pd
import sklearn.datasets as skd

data = skd.load_boston()
df_X = pd.DataFrame(data.data, columns=data.feature_names)
df_y = pd.DataFrame(data.target, columns=['y'])
df = pd.concat([df_X, df_y], axis=1)
df.to_csv('data.csv', index=True, index_label='ID')

`python data.When executed with py, data.csv is created.`


 After this, put it in the DB.

# Database preparation

 This time the database uses PostgreSQL, which is created when Redash is started.
 I want to bring the csv file and sql file to the container created by `` `docker-compose```, so mount the local folder.

 I want to change the docker-compose setting a little, so I added lines 61 and 62 for the following files.



#### **`docker-compose.yml `**
```yml 

(Omission)
50   postgres:
 51     image: postgres:9.5-alpine
 52     # The following turns the DB into less durable, but gains significant performance improvements for the tests run (x3
 53     # improvement on my personal machine). We should consider moving this into a dedicated Docker Compose configuration for
 54     # tests.
 55     ports:
 56       - "15432:5432"
 57     command: "postgres -c fsync=off -c full_page_writes=off -c synchronous_commit=OFF"
 58     restart: unless-stopped
 59     environment:
 60       POSTGRES_HOST_AUTH_METHOD: "trust"
 61     volumes:
 62       - ../data:/tmp/data
(Omission)

docker-compose buildWhendocker-compose up -dTo reflect the settings.

Create sql files for database creation and table creation.

`data/setup_db.sql`



DROP DATABASE IF EXISTS boston_datasets;

CREATE DATABASE boston_datasets;

`setup_tbl.sql`


CREATE TABLE realestate
(
ID INTEGER,
CRIM NUMERIC,
ZN NUMERIC,
INDUS NUMERIC,
CHAS NUMERIC,
NOX NUMERIC,
RM NUMERIC,
AGE NUMERIC,
DIS NUMERIC,
RAD NUMERIC,
TAX NUMERIC,
PTRATIO NUMERIC,
B NUMERIC,
LSTAT NUMERIC,
y NUMERIC
);

Execute the above two sql files.

$docker-compose run --rm postgres psql -f /tmp/data/setup_db.sql -h postgres -U postgres 
Creating redash_postgres_run ... done
DROP DATABASE
CREATE DATABASE

$cat  ../data/setup_db.sql 
DROP DATABASE IF EXISTS boston_datasets;

CREATE DATABASE boston_datasets;

(base) DyamaguchiMBA:redash $docker-compose run --rm postgres psql -f /tmp/data/setup_tbl.sql -h postgres -U postgres -d boston_datasets
Creating redash_postgres_run ... done
CREATE TABLE

Enter the container and check.

$docker exec -it redash_postgres_1 bash
bash-5.0# psql -U postgres -h postgres -d boston_datasets
psql (9.5.24)
Type "help" for help.

boston_datasets=# \dt
           List of relations
 Schema |    Name    | Type  |  Owner   
--------+------------+-------+----------
 public | realestate | table | postgres
(1 row)

boston_datasets=# \q
bash-5.0# exit

Certainly the real estate table has been created. Insert csv file data into this table.

$docker-compose run --rm postgres psql -h postgres -U postgres -d boston_datasets -c "copy realestate from  '/tmp/data/data.csv' encoding 'utf8' csv header delimiter ','"
Creating redash_postgres_run ... done
COPY 506

So far, the database, tables, and data are in PostgreSQL.

Redash settings

Next, let's check the connection from Redash to PostgreSQL. Basically, you should set it as shown in the figure below.

You can leave the Password blank here. Just in case, I performed Test Connection and confirmed the connection correctly.

Query issuance

If you select a data source from "Queries" on the left side of the screen, you can see the DB and table you created earlier. When I executed select * from realestate as SQL, the result was returned as shown in the figure below.

Summary

We carried out from data preparation to query issuance. Next, I would like to finally visualize it.

Try throwing a query in Redash