From 21534162124501f0410ee31cd31130aa3b92a9f3 Mon Sep 17 00:00:00 2001
From: Teddy Wing
Date: Mon, 10 Jun 2019 02:08:51 +0200
Subject: code-review-database(create_merge_base): Upsert merge base

Don't duplicate rows if we call `create_merge_base` multiple times.
Doing so would mean we'd get multiple merge base rows for the same head.

Instead, overwrite the existing merge base for a given head using an
upsert.

Thanks a bunch to MarqueIV
(https://stackoverflow.com/users/168179/marqueiv) on Stack Overflow for
demonstrating a way to do an upsert without the UPSERT syntax. This
enables us to do an upsert on SQLite < 3.24.0. Neat trick.
https://stackoverflow.com/questions/15277373/sqlite-upsert-update-or-insert/38463024#38463024
---
 code-review-database | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/code-review-database b/code-review-database
index 642f9c4..eb18818 100644
--- a/code-review-database
+++ b/code-review-database
@@ -31,13 +31,16 @@ function create_merge_base () {
 	sqlite3 "$DATABASE" <<-SQL
 		BEGIN TRANSACTION;
 
+		UPDATE merge_bases
+		SET base = '$base'
+		WHERE head = '$head';
+
 		INSERT INTO merge_bases
 			(head, base)
-		VALUES
-			(
-				'$head',
-				'$base'
-			);
+		SELECT
+			'$head',
+			'$base'
+		WHERE (SELECT changes() = 0);
 
 		COMMIT;
 	SQL
-- 
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