SQL

what is postgresql

PostgreSQL is a powerful, open source object-relational database system. It has more than 15 years of active development phase and a proven architecture that has earned it a strong reputation for reliability, data integrity, and correctness.

This tutorial will give you a quick start with PostgreSQL and make you comfortable with PostgreSQL programming.

What is PostgreSQL?
PostgreSQL (pronounced as post-gress-Q-L) is an open source relational database management system (DBMS) developed by a worldwide team of volunteers. PostgreSQL is not controlled by any corporation or other private entity and the source code is available free of charge.

postgres

Fun fact: "Postgres" has exactly as many characters as "Database"
Check for yourself!
Postgres --> 8 chars!
Database --> 8 chars!

postgreSQL

sudo mkdir -p /etc/paths.d &&
echo /Applications/Postgres.app/Contents/Versions/latest/bin | sudo tee /etc/paths.d/postgresapp

postgreSQL

$ sudo -i -u postgres
Code language: Shell Session (shell)

Postgresql

# The bash function below utilizes the CLI tool psql to vacuum analyze tables
# in a single schema which can be identified by either passing the name of
# the schema as the first parameter to the function
# or setting the environment variable PG_SCHEMA:
#

vacuum_analyze_schema() {
    # vacuum analyze only the tables in the specified schema

    # postgres info can be supplied by either passing it as parameters to this
    # function, setting environment variables or a combination of the two
    local pg_schema="${1:-${PG_SCHEMA}}"
    local pg_db="${2:-${PG_DB}}"
    local pg_user="${3:-${PG_USER}}"
    local pg_host="${4:-${PG_HOST}}"

    echo "Vacuuming schema `${pg_schema}`:"

    # extract schema table names from psql output and put them in a bash array
    local psql_tbls="dt ${pg_schema}.*"
    local sed_str="s/${pg_schema}s+|s+(w+)s+|.*/1/p"
    local table_names=$( echo "${psql_tbls}" | psql -d "${pg_db}" -U "${pg_user}" -h "${pg_host}"  | sed -nr "${sed_str}" )
    local tables_array=( $( echo "${table_names}" | tr '
' ' ' ) )

    # loop through the table names creating and executing a vacuum
    # command for each one
    for t in "${tables_array[@]}"; do
        echo "doing table `${t}`..."
        psql -d "${pg_db}" -U "${pg_user}" -h "${pg_host}" 
            -c "VACUUM (ANALYZE) ${pg_schema}.${t};"
    done
}

postgres

# Use postgres/example user/password credentials
version: '3.1'

services:

  db:
    image: postgres
    restart: always
    environment:
      POSTGRES_PASSWORD: example

  adminer:
    image: adminer
    restart: always
    ports:
      - 8080:8080

postgresql

CREATE OR REPLACE FUNCTION foo()
RETURNS void AS $$
BEGIN
  RAISE NOTICE 'Hello from void function';
END;
$$ LANGUAGE plpgsql;

-- direct call from SQL
SELECT foo();

-- in PLpgSQL
DO $$
BEGIN
  SELECT foo(); -- is not allowed
  PERFORM foo(); -- is ok
END;
$$;

postgres

$ sudo initdb --locale en_US.UTF-8 -D /var/lib/postgres/data
The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.

The database cluster will be initialized with locale "en_US.UTF-8".
The default database encoding has accordingly been set to "UTF8".
The default text search configuration will be set to "english".

Data page checksums are disabled.

fixing permissions on existing directory /var/lib/postgres/data ... ok
creating subdirectories ... ok
selecting dynamic shared memory implementation ... posix
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting default time zone ... Africa/Nairobi
creating configuration files ... ok
running bootstrap script ... ok
performing post-bootstrap initialization ... ok
syncing data to disk ... ok

initdb: warning: enabling "trust" authentication for local connections
You can change this by editing pg_hba.conf or using the option -A, or
--auth-local and --auth-host, the next time you run initdb.

Success. You can now start the database server using:

    pg_ctl -D /var/lib/postgres/data -l logfile start