Docker-Compose and Postgres Extensions - postgresql

Question

This is my docker-compose file. Is there any easy way to get a postgres extension installed? I'm trying to install pg_trgm.
Edit: I now have two dockerfiles and an install script. It doesn't seem to be working when I run docker-compose up build
Internal server error: pq: operator does not exist: character varying % unknown
services:
db:
build:
context: .
dockerfile: db/Dockerfile
image: postgres
ports:
- "5432:5432"
environment:
- POSTGRES_USER=x
- POSTGRES_PASSWORD=x
- POSTGRES_DB=x
api:
build:
context: .
args:
app_env: ${APP_ENV}
volumes:
- .:/go/src/x/y/z
ports:
- "8080:8080"
db/Dockerfile:
FROM postgres
COPY db/install-extensions.sql /docker-entrypoint-initdb.d
db/install-extensions.sql
CREATE EXTENSION IF NOT EXISTS pg_trgm;

Answer 1

Try this
FROM postgres
COPY ./install-extensions.sql /docker-entrypoint-initdb.d
and remove db from your file.
OR you can write
version: "3.1"
services:
db:
image: postgres:9.6
restart: always
environment:
POSTGRES_PASSWORD: unit
POSTGRES_USER: unit
POSTGRES_DB: unit
ports:
- 5432:5432
volumes:
- ./scripts:/docker-entrypoint-initdb.d
then
create directory scripts
put your .sql or .sh file
remove created containers docker-compose rm -v
start docker docker-compose up --build
in logs you must see something like this:
created_extension

Answer 2

I'm not sure precisely why but in order to get this working I had to use a shell script:
#!/usr/bin/env bash
echo "enabling pg_trgm on database $POSTGRES_DB"
psql -U $POSTGRES_USER --dbname="$POSTGRES_DB" <<-'EOSQL'
create extension if not exists pg_trgm;
EOSQL
echo "finished with exit code $?"
possibly because I was overriding the default database and user name.