Megaprog’s gists

Megaprog / sqrt.go

Last active March 10, 2024 09:36

Sqrt by Newton's method https://en.wikipedia.org/wiki/Newton%27s_method

	package main

	import (
	"fmt"
	"math"
	)

	func Sqrt(x float64) float64 {
	z := x / 2
	epsilon := 0.001

Megaprog / Main.kt

Created July 12, 2023 11:18

Spark local read from JDBC and write to parquet

	import org.apache.parquet.hadoop.ParquetOutputFormat
	import org.apache.spark.sql.SaveMode
	import org.apache.spark.sql.SparkSession

	fun main() {
	val session = createSparkSession("test", 1)

	val df = session.read().format("jdbc")
	.option("url", "jdbc:postgresql://localhost:6432/pg-atlas-v2-stg-other?user=postgres")
	.option("query", """select * from usdt_trx_udm_v2_transactions

Megaprog / build.gradle.kts

Created January 26, 2022 13:55

Kotlin integrationTest for Gradle 6 or 7

	sourceSets {
	create("integrationTest") {
	compileClasspath += main.get().output + configurations.testRuntimeClasspath
	runtimeClasspath += output + compileClasspath
	}
	}

	val integrationTestImplementation: Configuration by configurations.getting {
	extendsFrom(configurations.implementation.get())
	}

Megaprog / schema_size.sql

Created January 24, 2022 11:23

How to calculate schema space does the data take up. Regardles of https://stackoverflow.com/questions/4418403/list-of-schema-with-sizes-relative-and-absolute-in-a-postgresql-database

	SELECT schema_name,
	pg_size_pretty(sum(table_size)::bigint),
	(sum(table_size) / pg_database_size(current_database())) * 100
	FROM (
	SELECT pg_catalog.pg_namespace.nspname as schema_name,
	pg_relation_size(pg_catalog.pg_class.oid) as table_size
	FROM pg_catalog.pg_class
	JOIN pg_catalog.pg_namespace ON relnamespace = pg_catalog.pg_namespace.oid
	) t
	GROUP BY schema_name

Megaprog / pg_locks.sql

Last active September 13, 2022 04:23

How to see PG locks with advisory bigint hash

	select l.pid, relation::regclass, mode, a.application_name, a.query_start, locktype,
	(classid::bigint << 32) \| objid::bigint as hash
	from pg_locks l join pg_stat_activity a on l.pid = a.pid where granted;

Megaprog / supervisorScope_vs_SupervisorJob

Created December 1, 2021 10:47

CoroutineScope(coroutineContext + SupervisorJob()) and supervisorScope() look simular but behaviur is completly different. If you add SupervisorJob() then all jobs will be out of scope and when nobody will wait for them after scope finishes

	fun main() {
	runBlocking {
	repeat(10) {
	try {
	// CoroutineScope(coroutineContext + SupervisorJob()).run {
	supervisorScope {
	listOf(
	async {
	throw IllegalStateException("ERROR OCCURRED.")
	},

Megaprog / Postgres TimeZone psycopg2

Created August 30, 2021 17:37

	import psycopg2.extras

	# del os.environ["PGTZ"]
	# os.environ["PGTZ"]="UTC"
	# os.environ["PGTZ"]="Europe/Moscow"
	conn = psycopg2.connect(
	# host="postgres-corecms-slave.spb.play.dc",
	host="postgres-context-slave.spb.play.dc",
	port=5433,
	dbname="context",

Megaprog / Postgres TimeZone SQLAlchemy

Created August 30, 2021 17:35

	from sqlalchemy import create_engine

	engine = create_engine("postgresql://<name>:<password>@postgres-context-slave.spb.play.dc:5433/context", echo=True, connect_args={"options": "-c TimeZone=UTC"})

Megaprog / SimpleMessageListenerContainerLifeCycle.java

Last active July 13, 2021 02:22

How to start and stop SimpleMessageListenerContainer and wait a result

	val events = CopyOnWriteArrayList<UserSubscriptionExternalActivationEvent>()
	val listenerContainer = rabbitConfig.bind<UserSubscriptionExternalActivationEvent>(
	routingKey.externalActivation,
	TopicExchange(properties.template.exchange),
	) {
	println("result is $it")
	events.add(it)
	Mono.empty()
	}
	listenerContainer.start()

Megaprog / ValueFromMutex.rs

Created November 14, 2019 18:43

	use std::sync::{Arc, Mutex, MutexGuard};
	use std::collections::HashMap;
	use std::ops::Deref;

	pub struct Inner<'a>(MutexGuard<'a, HashMap<i32, Vec<i32>>>, i32);

	impl<'a> Deref for Inner<'a> {
	type Target = Vec<i32>;
	fn deref(&self) -> &Self::Target {
	self.0.get(&self.1).unwrap()

Tomas Shestakov Megaprog