Add tests and Github workflow (#1)

- Add comparison and arithmetic operators
- Add tests and Github workflow
- Improve the README

.github/workflows/main.yml

@@ -0,0 +1,21 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+      - main
+  pull_request:
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        pg: [16, 15, 14, 13, 12, 11, 10]
+    name: 🐘 PostgreSQL ${{ matrix.pg }}
+    runs-on: ubuntu-latest
+    container: pgxn/pgxn-tools
+    steps:
+      - run: pg-start ${{ matrix.pg }}
+      - uses: actions/checkout@v2
+      - run: pg-build-test

.gitignore

@@ -1,6 +1,8 @@
 *.o
 *.so
 
+.deps/
+
 test/results
 test/regression.diffs
 test/regression.out

Makefile

@@ -1,11 +1,15 @@
 EXTENSION = saturated_int
 MODULE_big = saturated_int
 
-PG_CONFIG ?= PG_CONFIG
+PG_CONFIG ?= pg_config
 
 DATA = $(wildcard *--*.sql)
 OBJS = $(patsubst %.c,%.o,$(wildcard src/*.c))
 
 PGXS := $(shell $(PG_CONFIG) --pgxs)
 
+TESTS = $(sort $(wildcard test/sql/*.sql))
+REGRESS = $(patsubst test/sql/%.sql,%,$(TESTS))
+REGRESS_OPTS = --inputdir=test --outputdir=test
+
 include $(PGXS)

README.md

@@ -1,3 +1,88 @@
 # pg-saturated_int
 
 An integer type with [saturation arithmetic](https://en.wikipedia.org/wiki/Saturation_arithmetic).
+The difference from builtin integer type is that if an input value is out of allowed range
+then the error `integer out of range` won't be raised.
+
+## Types
+
+### `saturated_int`
+
+`saturated_int` is an integer type which implements [saturation arithmetic](https://en.wikipedia.org/wiki/Saturation_arithmetic).
+Allowed range is `-2147483648` to `+2147483647`.
+
+```sql
+-- Cast to saturated_int
+
+select 999999999999999::saturated_int;
+ saturated_int 
+---------------
+ 2147483647
+
+select 2147483648::saturated_int;
+ saturated_int 
+---------------
+ 2147483647
+
+select (-2147483649)::saturated_int;
+ saturated_int 
+---------------
+ -2147483648
+```
+
+## Supported operators
+
+`saturated_int` supports comparison (`<`, `<=`, `<>`, `=`, `>`, `>=`) and arithmetic operators. Here is some examples:
+
+```sql
+select 999999999999999::saturated_int > 2147483648::saturated_int;
+ ?column? 
+----------
+ f
+
+select 999999999999999::saturated_int = 2147483648::saturated_int;
+ ?column? 
+----------
+ t
+
+select 999999999999999::saturated_int * 2147483648::saturated_int;
+  ?column?  
+------------
+ 2147483647
+
+select (-999999999999999)::saturated_int * 2147483648::saturated_int;
+  ?column?   
+-------------
+ -2147483648
+
+select 2147483648::saturated_int / (-1)::saturated_int;
+  ?column?   
+-------------
+ -2147483647
+```
+
+Note that it is necessary to explicitly cast both of operands to `saturated_int`. Implicit cast isn't supported:
+
+```sql
+select 2147483647::int = 2147483648::saturated_int;
+ERROR:  operator does not exist: integer = saturated_int at character 24
+
+select 2147483647::int * 2147483648::saturated_int;
+ERROR:  operator does not exist: integer * saturated_int at character 24
+```
+
+## Index support
+
+The extension supports `btree` and `hash` indexes.
+
+## Installation from source codes
+
+To install `saturated_int`, execute this in the extension's directory:
+
+```shell
+make install
+```
+
+> **Notice:** Don't forget to set the `PG_CONFIG` variable (`make PG_CONFIG=...`)
+> in case you want to test `saturated_int` on a non-default or custom build of PostgreSQL.
+> Read more [here](https://wiki.postgresql.org/wiki/Building_and_Installing_PostgreSQL_Extension_Modules).