R: Add minimal example

Author: amotl

.github/workflows/lang-r.yml

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+name: R
+
+on:
+  pull_request:
+    paths:
+    - '.github/workflows/lang-r.yml'
+    - 'by-language/r/**'
+    - '/requirements.txt'
+  push:
+    branches: [ main ]
+    paths:
+    - '.github/workflows/lang-r.yml'
+    - 'by-language/r/**'
+    - '/requirements.txt'
+
+  # Allow job to be triggered manually.
+  workflow_dispatch:
+
+  # Run job each night after CrateDB nightly has been published.
+  schedule:
+    - cron: '0 3 * * *'
+
+# Cancel in-progress jobs when pushing to the same branch.
+concurrency:
+  cancel-in-progress: true
+  group: ${{ github.workflow }}-${{ github.ref }}
+
+jobs:
+
+  test:
+    name: "
+     CrateDB: ${{ matrix.cratedb-version }}
+     on ${{ matrix.os }}"
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ 'ubuntu-latest' ]
+        cratedb-version: [ 'nightly' ]
+
+    services:
+      cratedb:
+        image: crate/crate:${{ matrix.cratedb-version }}
+        ports:
+          - 4200:4200
+          - 5432:5432
+        env:
+          CRATE_HEAP_SIZE: 4g
+
+    steps:
+
+      - name: Acquire sources
+        uses: actions/checkout@v4
+
+      - name: Install R
+        uses: r-lib/actions/setup-r@v2
+
+      - name: Install utilities
+        run: |
+          pip install -r requirements.txt
+
+      - name: Validate by-language/r
+        run: |
+          ngr test by-language/r

by-language/r/.gitignore

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+.RData
+.Rhistory

by-language/r/Makefile

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+install:
+
+test:
+	Rscript basic.r

by-language/r/README.md

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+# Connecting to CrateDB with R
+
+## About
+
+The file `basic.r` includes a basic example program that uses the R
+[RPostgreSQL] package, the canonical database interface and 'PostgreSQL'
+driver for 'R', to connect to CrateDB.
+
+## Usage
+
+Start a CrateDB instance for evaluation purposes.
+```shell
+docker run -it --rm --publish=4200:4200 --publish=5432:5432 crate:latest
+```
+
+Invoke example program.
+```shell
+Rscript basic.r
+```
+
+Invoke software tests.
+```shell
+make test
+```
+
+
+[RPostgreSQL]: https://cran.r-project.org/web/packages/RPostgreSQL/

by-language/r/backlog.md

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+# Backlog for R with CrateDB
+
+## Bugs
+
+- `SELECT * FROM sys.summits` will fail like:
+  ```
+  RPosgreSQL warning: unrecognized PostgreSQL field type point (id:600) in column 1
+  ```

by-language/r/basic.r

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+# Install driver on demand.
+# RPostgreSQL: R Interface to the 'PostgreSQL' Database System
+# https://cran.r-project.org/web/packages/RPostgreSQL/
+if (!require(RPostgreSQL)) {
+    install.packages("RPostgreSQL", repos="http://cran.us.r-project.org")
+}
+stopifnot(require(RPostgreSQL))
+
+# Load the DBI library.
+library(DBI)
+drv <- dbDriver("PostgreSQL")
+
+# Open a database connection, where `dbname` is the name of the CrateDB schema.
+con <- dbConnect(drv,
+                 host = "localhost",
+                 port = 5432,
+                 user = "crate",
+                 dbname = "testdrive",
+                 )
+
+# Invoke a basic select query.
+res <- dbGetQuery(con, "SELECT mountain, region, height FROM sys.summits ORDER BY HEIGHT DESC LIMIT 10;")
+print(res)
+
+# Delete testdrive table when needed.
+if (dbExistsTable(con, "r")) {
+    dbRemoveTable(con, "r")
+}
+
+# Basic I/O.
+res <- dbGetQuery(con, "CREATE TABLE IF NOT EXISTS r (id INT PRIMARY KEY, data TEXT);")
+res <- dbGetQuery(con, "INSERT INTO r (id, data) VALUES (42, 'foobar');")
+res <- dbGetQuery(con, "REFRESH TABLE r;")
+res <- dbGetQuery(con, "SELECT * FROM r;")
+print(res)