steve-chavez

Nix String and Path Concatenation

From Bas van Dijk:

To understand these things I would recommend using nix-repl:

$ nix-repl
Welcome to Nix version 1.11.2. Type :? for help.

steve-chavez

-- Usage with nix:
-- nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ optparse-applicative random ])" --run "runhaskell Main User Minimax"
-- Then input the numbers (1-9) that represent the position of the mark
--
-- runhaskell Main User Random (first play User)
-- runhaskell Main Minimax User (second play User)
-- Using MiniMax can take a while
--
module Main where

steve-chavez

docker run -d -p 5433:5432 pipelinedb/pipelinedb:0.9.9

PGPASSWORD=pipeline psql -h localhost -p 5433 -U pipeline -d pipeline <<EOF
  CREATE STREAM wiki_stream (hour timestamp, project text, title text, view_count bigint, size bigint);

  CREATE CONTINUOUS VIEW wiki_stats AS
  SELECT hour, project,
          count(*) AS total_pages,
          sum(view_count) AS total_views,
          min(view_count) AS min_views,

steve-chavez

Download Audio from YouTube

-i - ignore errors

-c - continue

-t - use video title as file name

--extract-audio - extract audio track

steve-chavez

version: '3'
services:
  db:
    image: timescale/timescaledb:latest-pg10
    ports:
      - "5432:5432"
    environment:
      POSTGRES_DB: devices_small
      POSTGRES_USER: app_user
  pgrest:

steve-chavez

# Minimal example of getting a PostgREST API running from scratch for
# testing purposes.  It uses docker to launch a postgres database and
# a postgrest api server.

# This should not be used to deploy a production system but to
# understand how postgrest works.  In particular there is no security
# implemented, see the docs for more.

# https://postgrest.org/en/v4.4/

steve-chavez

%.hex: %.asm
	avra -fI $<
	rm *.eep.hex *.obj *.cof

all: $(patsubst %.asm,%.hex,$(wildcard *.asm))

upload: ${program}.hex
	avrdude -c arduino -p m328p -P /dev/arduino-uno -b 115200 -U flash:w:$<

monitor:

steve-chavez

-- child embed, cte better cost, almost half of subselect

-- cost=31864.78..31864.80
explain WITH pg_source AS (
  SELECT  "test"."clients".*, COALESCE((SELECT array_to_json(array_agg(row_to_json("projects".*))) FROM (SELECT  "test"."projects"."name" FROM  "test"."projects"  WHERE  "test"."projects"."client_id" = "test"."clients"."id"  ) "projects"), '[]') AS "projects" FROM  "test"."clients"    
) SELECT null AS total_result_set, 
         pg_catalog.count(_postgrest_t) AS page_total, 
         array[]::text[] AS header, 
         coalesce(array_to_json(array_agg(row_to_json(_postgrest_t))), '[]')::character varying AS body
FROM ( SELECT * FROM pg_source) _postgrest_t;

steve-chavez

select current_setting('response.smth', true) is null; -- gives true
begin;
set local "response.smth" = 'value';
commit; -- or rollback
select current_setting('response.smth', true) is null; -- gives false since current_setting('response.smth') now is equal to ''

steve-chavez

-- Prior 9.6 \setrandom :rid 1 999900
\set rid random(1, 999900)

BEGIN ISOLATION LEVEL READ COMMITTED READ ONLY;

WITH pg_source AS
  (SELECT "parent_query_test"."items"."id",
          "parent_query_test"."items"."name",
          row_to_json("parent_items_parent_items".*) AS "parent_items"
   FROM "parent_query_test"."items"