From e2c19024a21d51bd49697a3642e30d5d30c73a22 Mon Sep 17 00:00:00 2001
From: Guntis Smaukstelis <gsmaukstelis@evolution.com>
Date: Sun, 22 Oct 2023 21:19:11 +0300
Subject: [PATCH] Select from table in postgres

---
 src/main/scala/db/Postgres.scala | 33 +++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/main/scala/db/Postgres.scala b/src/main/scala/db/Postgres.scala
index 3dae26c..de9060c 100644
--- a/src/main/scala/db/Postgres.scala
+++ b/src/main/scala/db/Postgres.scala
@@ -1,5 +1,6 @@
 package db
 
+import cats.data.NonEmptyList
 import cats.effect._
 import cats.effect.unsafe.implicits.global
 import doobie._
@@ -62,6 +63,35 @@ object Postgres {
     } yield result
   }
 
+  def selectWeatherTable(xa: Transactor[IO]): IO[List[(String, Option[Double])]] = {
+    val formatter = DateTimeFormatter.ofPattern("yyyyMMdd_HHmm")
+    val rigaZone = ZoneId.of("Europe/Riga")
+    val from = LocalDateTime.parse("20230516_0100", formatter).atZone(rigaZone)
+    val to = LocalDateTime.parse("20230516_1500", formatter).atZone(rigaZone)
+    val citiesNel = NonEmptyList.of("Rīga", "Rēzekne")
+    val granularity = "HOUR" // "HOUR", "DAY", "MONTH", "YEAR"
+    val columnName = "tempMin"
+
+    val baseQuery =
+      fr"""
+        SELECT
+          city,
+          MIN(""" ++ Fragment.const(columnName) ++
+        fr""") AS tempMin
+        FROM weather
+        WHERE
+          """ ++ Fragments.in(fr"city", citiesNel) ++ fr"""
+          AND dateTime BETWEEN $from AND $to
+          AND """ ++ Fragment.const(columnName) ++fr""" IS NOT NULL
+        GROUP BY city, EXTRACT(""" ++ Fragment.const(granularity) ++ fr""" FROM dateTime)
+      """
+
+    baseQuery
+      .query[(String, Option[Double])]
+      .to[List]
+      .transact(xa)
+  }
+
   def dropWeatherTable(implicit xa: Transactor[IO]): IO[Int] = {
     for {
       dropTableSql <- getResourceContent("/db/drop_weather_table.sql")
@@ -73,7 +103,8 @@ object Postgres {
     val xa = transactor[IO]
 
 //    val result = createWeatherTable(xa).unsafeRunSync()
-    val result = insertInWeatherTable(xa).unsafeRunSync()
+//    val result = insertInWeatherTable(xa).unsafeRunSync()
+    val result = selectWeatherTable(xa).unsafeRunSync()
 //    val result = dropWeatherTable(xa).unsafeRunSync()
 
     println(s"result: $result")