Category: Computers

All things computing.

Query for Finding an Element in a PostgreSQL JSONB Array

Posted on by rchapin

The following is a sample query that you can use to search for rows that have an element in a JSONB array.

Given

CREATE TABLE sample_jsonb (
  id serial PRIMARY KEY,
  name varchar(64),
  json_data jsonb
);

INSERT INTO sample_jsonb(name, json_data)
VALUES
  ('foo',
  '{
  "key": "val1",
  "arr": ["homer", "bart", "barney"]
  }'),
  ('bar',
  '{
  "key": "val2",
  "arr": ["marge", "lisa", "maggie"]
  }')
;

select count(*) from sample_jsonb where json_data-'arr' ? 'marge';
→ Continue reading “Query for Finding an Element in a PostgreSQL JSONB Array”

Convert a Slice of Any Type to a CSV in Go

Posted on by rchapin

There are times, mostly for logging and debugging, when you have a slice of a given type that you would like to print to a log file or just convert to a CSV of values.

A quick and easy way to convert a slice to a CSV in Golang is to use the json module to Marshal it a JSON encoded array.

For example

package main

import (
	"encoding/json"
	"fmt"
)

func main() {
	ints := []int64{1, 2, 3,
→ Continue reading “Convert a Slice of Any Type to a CSV in Go”

PostgreSQL Query to Find Tables With Name LIKE

Posted on by rchapin

Sometimes you are working with a PostgreSQL database with A LOT of tables and looking for tables that contain a sub-string in their name. Following is a query that you can run that will return all of the tables that have the string in their name:

SELECT
  table_schema,
  table_name
FROM
  information_schema.tables
WHERE
      table_name LIKE '%<string%'
  AND table_schema not in ('information_schema', 'pg_catalog')
  AND table_type = 'BASE TABLE'
ORDER BY
  table_name, table_schema
;
→ Continue reading “PostgreSQL Query to Find Tables With Name LIKE”

Earthly Cheat Sheet

Posted on by rchapin

I have just recently started using Earthly and the following is a list of commands that I want to keep track of

Caching

Completely clearing the cache: Earthly stores artifacts in docker volumes. If you want to completely flush that data and start fresh run the following

docker stop earthly-buildkitd && \
docker rm earthly-buildkitd && \
docker volume rm earthly-cache
→ Continue reading “Earthly Cheat Sheet”

git Cheat Sheet

Posted on by rchapin

A handful of handy git commands that I don’t use all that often but want to keep track of:

Stashing

Stash a single file

git stash push -m 'message here' -- path/to/file

Drop a specific stash

First figure out the id of the stash you want to drop with git stash list, then issue the following command

git stash drop stash@{n}

Editing Commits

Changing author of already pushed commit

If you need to change the author of a commit → Continue reading “git Cheat Sheet”

Use printf to join an array in Bash

Posted on by rchapin

If you would like to join an array of elements with a defined delimiter in Bash there is an easy way to go about it by using printf. Following is an example

#!/bin/bash

declare -a arr=()

for i in `seq 1 5`
do
  arr=("${arr[@]}" $i)
done

# Generate a single string joined by a comma.  The printf string can contain
# any arbitrary delimiter.
printf -v joined '%s,' "${arr[@]}"

# Print out the string minus the trailing comma
echo
→ Continue reading “Use printf to join an array in Bash”

Specifying a commit in go.mod instead of a local replace for development

Posted on by rchapin

Sometimes you are making changes to a dependency in another of your go projects and instead of adding a replace command in the go.mod file you want to update that entry in go.mod to point to a specific commit in the repo.

To do so, all that you need to do is:

  1. Get the git commit that you want included in your build
  2. Change directories to the same directory that your project’s go.mod file resides in which you want to
→ Continue reading “Specifying a commit in go.mod instead of a local replace for development”

Using Microsoft PowerRename to Rename Batches of Files

Posted on by rchapin

If you have to rename a large number of files under Windows it is very tedious to do it one-by-one via the gui. Instead of writing a batch file, Microsoft has a suite of tools called PowerToys. PowerToys installs a utility called PowerRename that will do the job.

I did this under Windows 10, but I imagine that it is the same in Windows 11 based on the documentation on the PowerToys installation page.

Installation

  1. Start a PowerShell as
→ Continue reading “Using Microsoft PowerRename to Rename Batches of Files”

Docker Cheat Sheet

Posted on by rchapin

Following are a number of my commonly used docker commands for my own reference

Building

Run the following in the same directory in which your Dockerfile resides

docker build -t <image-name>:<version> .

Or you can specify the path to the Dockerfile

docker build . -t <image-name>:<version> -f /path/to/Dockerfile

Running

Run a container interactively

Especially useful when debugging commands that you will encapsulate in a Docker file, this will enable you to run a base image and then execute commands interactively → Continue reading “Docker Cheat Sheet”

Git Merge Conflict Resolution Cheat Sheet

Posted on by rchapin

Some of git’s nomenclature can be confusing, especially since it is context dependent. Following are some TLDR;s for dealing with resolving merge conflicts in different scenarios.

–ours vs –theirs

The meaning of --ours vs --theirs can depend on whether you are doing a rebase or a merge.

Assuming that the feature branch is checked out

git merge developgit rebase develop
To keep changes from develop--theirs--ours
To keep changes from feature--ours--theirs

If, during a rebase there → Continue reading “Git Merge Conflict Resolution Cheat Sheet”

© 2005 Ryan Chapin