/etc/conf.d/postgresql from posgresql-openrc, adjusted to work on artix with the postgresql package.

postgresql

# Comma-separated list of directories that contain a unix
# socket. Created and controlled by the related initscript. The
# directories created will be owned root:postgres with mode 1775.
#
# /run/postgresql is the default directory.
PG_SOCKET_DIRECTORIES="/run/postgresql"

# Which port and socket to bind PostgreSQL
PGPORT="5432"

# How long to wait for server to start in seconds
START_TIMEOUT=10

# NICE_QUIT ignores new connections and wait for clients to disconnect from
# server before shutting down. NICE_TIMEOUT in seconds determines how long to
# wait for this to succeed.
NICE_TIMEOUT=60

# Forecfully disconnect clients from server and shut down. This is performed
# after NICE_QUIT. Terminated client connections have their open transactions
# rolled back.
# Set RUDE_QUIT to "NO" to disable. RUDE_TIMEOUT in seconds.
RUDE_QUIT="YES"
RUDE_TIMEOUT=30

# If the server still fails to shutdown, you can force it to quit by setting
# this to YES and a recover-run will execute on the next startup.
# Set FORCE_QUIT to "YES" to enable. FORCE_TIMEOUT in seconds.
FORCE_QUIT="NO"
FORCE_TIMEOUT=2

# Extra options to run postmaster with, e.g.:
# -N is the maximal number of client connections
# -B is the number of shared buffers and has to be at least 2x the value for -N
# Please read the man-page to postmaster for more options. Many of these
# options can be set directly in the configuration file.
#PGOPTS="-N 512 -B 1024"

# Pass extra environment variables. If you have to export environment variables
# for the database process, this can be done here.
# Don't forget to escape quotes.
#PG_EXTRA_ENV="PGPASSFILE=\"/path/to/.pgpass\""

##############################################################################
#
# The following values should not be arbitrarily changed.
#
# uses these values to
# determine where to create the data directory, where to place the
# configuration files, and any additional options to pass to initdb.
#
# The initscript also uses these variables to inform PostgreSQL where to find
# its data directory and configuration files.
#
##############################################################################

# Location of configuration files
PGDATA="/var/lib/postgres/data/"

# Where the data directory is located/to be created
DATA_DIR="/var/lib/postgres/data"

# Additional options to pass to initdb.
# See `man initdb' for available options.
PG_INITDB_OPTS="--encoding=UTF8"
gammy@hypatia:/etc/conf.d$ diff -rcs /tmp/postgresql.orig postgresql ^C
gammy@hypatia:/etc/conf.d$ vim postgresql 
gammy@hypatia:/etc/conf.d$ cat /etc/conf.d/postgresql 
# Comma-separated list of directories that contain a unix
# socket. Created and controlled by the related initscript. The
# directories created will be owned root:postgres with mode 1775.
#
# /run/postgresql is the default directory.
PG_SOCKET_DIRECTORIES="/run/postgresql"

# Which port and socket to bind PostgreSQL
PGPORT="5432"

# How long to wait for server to start in seconds
START_TIMEOUT=10

# NICE_QUIT ignores new connections and wait for clients to disconnect from
# server before shutting down. NICE_TIMEOUT in seconds determines how long to
# wait for this to succeed.
NICE_TIMEOUT=60

# Forecfully disconnect clients from server and shut down. This is performed
# after NICE_QUIT. Terminated client connections have their open transactions
# rolled back.
# Set RUDE_QUIT to "NO" to disable. RUDE_TIMEOUT in seconds.
RUDE_QUIT="YES"
RUDE_TIMEOUT=30

# If the server still fails to shutdown, you can force it to quit by setting
# this to YES and a recover-run will execute on the next startup.
# Set FORCE_QUIT to "YES" to enable. FORCE_TIMEOUT in seconds.
FORCE_QUIT="NO"
FORCE_TIMEOUT=2

# Extra options to run postmaster with, e.g.:
# -N is the maximal number of client connections
# -B is the number of shared buffers and has to be at least 2x the value for -N
# Please read the man-page to postmaster for more options. Many of these
# options can be set directly in the configuration file.
#PGOPTS="-N 512 -B 1024"

# Pass extra environment variables. If you have to export environment variables
# for the database process, this can be done here.
# Don't forget to escape quotes.
#PG_EXTRA_ENV="PGPASSFILE=\"/path/to/.pgpass\""

##############################################################################
#
# The following values should not be arbitrarily changed.
#
# uses these values to
# determine where to create the data directory, where to place the
# configuration files, and any additional options to pass to initdb.
#
# The initscript also uses these variables to inform PostgreSQL where to find
# its data directory and configuration files.
#
##############################################################################

# Location of configuration files
PGDATA="/var/lib/postgres/data/"

# Where the data directory is located/to be created
DATA_DIR="/var/lib/postgres/data"

# Additional options to pass to initdb.
# See `man initdb' for available options.
PG_INITDB_OPTS="--encoding=UTF8"

postres_tmp_diff.patch

--- /tmp/postgresql.orig	2019-03-08 21:13:26.161549600 +0100
+++ /etc/conf.d/postgresql	2019-03-08 21:13:00.781862442 +0100
@@ -55,10 +55,10 @@
 ##############################################################################
 
 # Location of configuration files
-PGDATA="/etc/postgresql/"
+PGDATA="/var/lib/postgres/data/"
 
 # Where the data directory is located/to be created
-DATA_DIR="/var/lib/postgresql/data"
+DATA_DIR="/var/lib/postgres/data"
 
 # Additional options to pass to initdb.
 # See `man initdb' for available options.