From 9b397878dc69928d3c2814fbb8fce345816874e8 Mon Sep 17 00:00:00 2001
From: Wolfgang Walther <walther@technowledgy.de>
Date: Tue, 30 Nov 2021 17:52:27 +0100
Subject: [PATCH] refactor: Make asJsonSingleF "safe", by accessing only the
 first element of a json_agg result

---
 src/PostgREST/Query/SqlFragment.hs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/PostgREST/Query/SqlFragment.hs b/src/PostgREST/Query/SqlFragment.hs
index e35a8c2dc..fb1941212 100644
--- a/src/PostgREST/Query/SqlFragment.hs
+++ b/src/PostgREST/Query/SqlFragment.hs
@@ -172,10 +172,10 @@ asJsonF returnsScalar
   | returnsScalar = "coalesce(json_agg(_postgrest_t.pgrst_scalar), '[]')::character varying"
   | otherwise     = "coalesce(json_agg(_postgrest_t), '[]')::character varying"
 
-asJsonSingleF :: Bool -> SqlFragment --TODO! unsafe when the query actually returns multiple rows, used only on inserting and returning single element
+asJsonSingleF :: Bool -> SqlFragment
 asJsonSingleF returnsScalar
-  | returnsScalar = "coalesce(string_agg(to_json(_postgrest_t.pgrst_scalar)::text, ','), 'null')::character varying"
-  | otherwise     = "coalesce(string_agg(to_json(_postgrest_t)::text, ','), '')::character varying"
+  | returnsScalar = "coalesce((json_agg(_postgrest_t.pgrst_scalar)->0)::text, 'null')"
+  | otherwise     = "coalesce((json_agg(_postgrest_t)->0)::text, 'null')"
 
 asBinaryF :: FieldName -> SqlFragment
 asBinaryF fieldName = "coalesce(string_agg(_postgrest_t." <> pgFmtIdent fieldName <> ", ''), '')"