diff --git a/sql/010-core.sql b/sql/010-core.sql
index b85a9eb..9b48c85 100644
--- a/sql/010-core.sql
+++ b/sql/010-core.sql
@@ -159,125 +159,145 @@ ALTER DOMAIN cs_encrypted_v1
 );
 
 
-DROP FUNCTION IF EXISTS cs_ciphertext_v1_v0_0(col jsonb);
+DROP FUNCTION IF EXISTS cs_ciphertext_v1_v0_0(val jsonb);
 
-CREATE FUNCTION cs_ciphertext_v1_v0_0(col jsonb)
-    RETURNS text
-  LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
-BEGIN ATOMIC
-	RETURN col->>'c';
-END;
+CREATE FUNCTION cs_ciphertext_v1_v0_0(val jsonb)
+  RETURNS text
+  IMMUTABLE STRICT PARALLEL SAFE
+AS $$
+	BEGIN
+    IF val ? 'c' THEN
+      RETURN val->>'c';
+    END IF;
+    RAISE 'Expected a ciphertext (c) value in json: %', val;
+  END;
+$$ LANGUAGE plpgsql;
 
 
-DROP FUNCTION IF EXISTS cs_ciphertext_v1_v0(col jsonb);
+DROP FUNCTION IF EXISTS cs_ciphertext_v1_v0(val jsonb);
 
-CREATE FUNCTION cs_ciphertext_v1_v0(col jsonb)
+CREATE FUNCTION cs_ciphertext_v1_v0(val jsonb)
     RETURNS text
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_ciphertext_v1_v0_0(col);
+	RETURN cs_ciphertext_v1_v0_0(val);
 END;
 
 
-DROP FUNCTION IF EXISTS cs_ciphertext_v1(col jsonb);
+DROP FUNCTION IF EXISTS cs_ciphertext_v1(val jsonb);
 
-CREATE FUNCTION cs_ciphertext_v1(col jsonb)
+CREATE FUNCTION cs_ciphertext_v1(val jsonb)
     RETURNS text
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_ciphertext_v1_v0_0(col);
+	RETURN cs_ciphertext_v1_v0_0(val);
 END;
 
 
 -- extracts match index from an emcrypted column
-DROP FUNCTION IF EXISTS cs_match_v1_v0_0(col jsonb);
+DROP FUNCTION IF EXISTS cs_match_v1_v0_0(val jsonb);
 
-CREATE FUNCTION cs_match_v1_v0_0(col jsonb)
+CREATE FUNCTION cs_match_v1_v0_0(val jsonb)
   RETURNS cs_match_index_v1
-  LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
-BEGIN ATOMIC
-	SELECT ARRAY(SELECT jsonb_array_elements(col->'m'))::cs_match_index_v1;
-END;
+  IMMUTABLE STRICT PARALLEL SAFE
+AS $$
+	BEGIN
+    IF val ? 'm' THEN
+      RETURN ARRAY(SELECT jsonb_array_elements(val->'m'))::cs_match_index_v1;
+    END IF;
+    RAISE 'Expected a match index (m) value in json: %', val;
+  END;
+$$ LANGUAGE plpgsql;
 
 
-DROP FUNCTION IF EXISTS  cs_match_v1_v0(col jsonb);
+DROP FUNCTION IF EXISTS cs_match_v1_v0(val jsonb);
 
-CREATE FUNCTION cs_match_v1_v0(col jsonb)
+CREATE FUNCTION cs_match_v1_v0(val jsonb)
   RETURNS cs_match_index_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_match_v1_v0_0(col);
+	RETURN cs_match_v1_v0_0(val);
 END;
 
 
-DROP FUNCTION IF EXISTS cs_match_v1(col jsonb);
+DROP FUNCTION IF EXISTS cs_match_v1(val jsonb);
 
-CREATE FUNCTION cs_match_v1(col jsonb)
+CREATE FUNCTION cs_match_v1(val jsonb)
   RETURNS cs_match_index_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_match_v1_v0_0(col);
+	RETURN cs_match_v1_v0_0(val);
 END;
 
 
 -- extracts unique index from an encrypted column
-DROP FUNCTION IF EXISTS  cs_unique_v1_v0_0(col jsonb);
+DROP FUNCTION IF EXISTS  cs_unique_v1_v0_0(val jsonb);
 
-CREATE FUNCTION cs_unique_v1_v0_0(col jsonb)
+CREATE FUNCTION cs_unique_v1_v0_0(val jsonb)
   RETURNS cs_unique_index_v1
-  LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
-BEGIN ATOMIC
-	RETURN col->>'u';
-END;
+  IMMUTABLE STRICT PARALLEL SAFE
+AS $$
+	BEGIN
+    IF val ? 'u' THEN
+      RETURN val->>'u';
+    END IF;
+    RAISE 'Expected a unique index (u) value in json: %', val;
+  END;
+$$ LANGUAGE plpgsql;
 
 
-DROP FUNCTION IF EXISTS  cs_unique_v1_v0(col jsonb);
+DROP FUNCTION IF EXISTS  cs_unique_v1_v0(val jsonb);
 
-CREATE FUNCTION cs_unique_v1_v0(col jsonb)
+CREATE FUNCTION cs_unique_v1_v0(val jsonb)
   RETURNS cs_unique_index_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_unique_v1_v0_0(col);
+	RETURN cs_unique_v1_v0_0(val);
 END;
 
 
-DROP FUNCTION IF EXISTS  cs_unique_v1(col jsonb);
+DROP FUNCTION IF EXISTS  cs_unique_v1(val jsonb);
 
-CREATE FUNCTION cs_unique_v1(col jsonb)
+CREATE FUNCTION cs_unique_v1(val jsonb)
   RETURNS cs_unique_index_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_unique_v1_v0_0(col);
+	RETURN cs_unique_v1_v0_0(val);
 END;
 
 -- extracts json ste_vec index from an encrypted column
-DROP FUNCTION IF EXISTS cs_ste_vec_v1_v0_0(col jsonb);
+DROP FUNCTION IF EXISTS cs_ste_vec_v1_v0_0(val jsonb);
 
-CREATE FUNCTION cs_ste_vec_v1_v0_0(col jsonb)
+CREATE FUNCTION cs_ste_vec_v1_v0_0(val jsonb)
   RETURNS cs_ste_vec_index_v1
-  LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
-BEGIN ATOMIC
-	SELECT (col->'sv')::cs_ste_vec_index_v1;
-END;
+  IMMUTABLE STRICT PARALLEL SAFE
+AS $$
+	BEGIN
+    IF val ? 'sv' THEN
+      RETURN (val->'sv')::cs_ste_vec_index_v1;
+    END IF;
+    RAISE 'Expected a structured vector index (sv) value in json: %', val;
+  END;
+$$ LANGUAGE plpgsql;
 
 
-DROP FUNCTION IF EXISTS cs_ste_vec_v1_v0(col jsonb);
+DROP FUNCTION IF EXISTS cs_ste_vec_v1_v0(val jsonb);
 
-CREATE FUNCTION cs_ste_vec_v1_v0(col jsonb)
+CREATE FUNCTION cs_ste_vec_v1_v0(val jsonb)
   RETURNS cs_ste_vec_index_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_ste_vec_v1_v0_0(col);
+	RETURN cs_ste_vec_v1_v0_0(val);
 END;
 
 
-DROP FUNCTION IF EXISTS cs_ste_vec_v1(col jsonb);
+DROP FUNCTION IF EXISTS cs_ste_vec_v1(val jsonb);
 
-CREATE FUNCTION cs_ste_vec_v1(col jsonb)
+CREATE FUNCTION cs_ste_vec_v1(val jsonb)
   RETURNS cs_ste_vec_index_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_ste_vec_v1_v0_0(col);
+	RETURN cs_ste_vec_v1_v0_0(val);
 END;
 
 
@@ -303,39 +323,31 @@ DROP FUNCTION IF EXISTS cs_ore_64_8_v1_v0_0(val jsonb);
 
 CREATE FUNCTION cs_ore_64_8_v1_v0_0(val jsonb)
   RETURNS ore_64_8_v1
-  LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
-BEGIN ATOMIC
-  SELECT (val->>'o')::ore_64_8_v1;
-END;
+  IMMUTABLE STRICT PARALLEL SAFE
+AS $$
+	BEGIN
+    IF val ? 'o' THEN
+      RETURN (val->>'o')::ore_64_8_v1;
+    END IF;
+    RAISE 'Expected an ore index (o) value in json: %', val;
+  END;
+$$ LANGUAGE plpgsql;
+
 
-DROP FUNCTION IF EXISTS cs_ore_64_8_v1_v0(col jsonb);
+DROP FUNCTION IF EXISTS cs_ore_64_8_v1_v0(val jsonb);
 
-CREATE FUNCTION cs_ore_64_8_v1_v0(col jsonb)
+CREATE FUNCTION cs_ore_64_8_v1_v0(val jsonb)
   RETURNS ore_64_8_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_ore_64_8_v1_v0_0(col);
+	RETURN cs_ore_64_8_v1_v0_0(val);
 END;
 
-DROP FUNCTION IF EXISTS cs_ore_64_8_v1(col jsonb);
+DROP FUNCTION IF EXISTS cs_ore_64_8_v1(val jsonb);
 
-CREATE FUNCTION cs_ore_64_8_v1(col jsonb)
+CREATE FUNCTION cs_ore_64_8_v1(val jsonb)
   RETURNS ore_64_8_v1
   LANGUAGE sql IMMUTABLE STRICT PARALLEL SAFE
 BEGIN ATOMIC
-	RETURN cs_ore_64_8_v1_v0_0(col);
+	RETURN cs_ore_64_8_v1_v0_0(val);
 END;
-
-DROP FUNCTION IF EXISTS _cs_first_grouped_value(jsonb, jsonb);
-
-CREATE FUNCTION _cs_first_grouped_value(jsonb, jsonb)
-RETURNS jsonb AS $$
-  SELECT COALESCE($1, $2);
-$$ LANGUAGE sql IMMUTABLE;
-
-DROP AGGREGATE IF EXISTS cs_grouped_value_v1(jsonb);
-
-CREATE AGGREGATE cs_grouped_value_v1(jsonb) (
-  SFUNC = _cs_first_grouped_value,
-  STYPE = jsonb
-);
diff --git a/tests/core-functions.sql b/tests/core-functions.sql
new file mode 100644
index 0000000..792a7e3
--- /dev/null
+++ b/tests/core-functions.sql
@@ -0,0 +1,79 @@
+\set ON_ERROR_STOP on
+
+
+DO $$
+  BEGIN
+    ASSERT (SELECT EXISTS (SELECT cs_unique_v1('{"u": "u"}'::jsonb)));
+    ASSERT (SELECT EXISTS (SELECT cs_match_v1('{"m": []}'::jsonb)));
+    ASSERT (SELECT EXISTS (SELECT cs_ste_vec_v1('{"sv": [[]]}'::jsonb)));
+    ASSERT (SELECT EXISTS (SELECT cs_ore_64_8_v1('{"o": "()"}'::jsonb)));
+
+  END;
+$$ LANGUAGE plpgsql;
+
+DO $$
+  BEGIN
+    -- sanity check
+    PERFORM cs_ore_64_8_v1('{"o": "()"}'::jsonb);
+
+    BEGIN
+      PERFORM cs_ore_64_8_v1('{}'::jsonb);
+      RAISE NOTICE 'Missing index. Function call should have failed.';
+      ASSERT false;
+    EXCEPTION
+      WHEN OTHERS THEN
+        ASSERT true;
+    END;
+  END;
+$$ LANGUAGE plpgsql;
+
+DO $$
+  BEGIN
+    -- sanity check
+    PERFORM cs_ste_vec_v1('{"sv": [[]]}'::jsonb);
+
+    BEGIN
+      PERFORM cs_ste_vec_v1('{}'::jsonb);
+      RAISE NOTICE 'Missing index. Function call should have failed.';
+      ASSERT false;
+    EXCEPTION
+      WHEN OTHERS THEN
+        ASSERT true;
+    END;
+  END;
+$$ LANGUAGE plpgsql;
+
+
+DO $$
+  BEGIN
+    -- sanity check
+    PERFORM cs_unique_v1('{"u": "u"}'::jsonb);
+
+    BEGIN
+      PERFORM cs_unique_v1_v0('{}'::jsonb);
+      RAISE NOTICE 'Missing index. Function call should have failed.';
+      ASSERT false;
+    EXCEPTION
+      WHEN OTHERS THEN
+        ASSERT true;
+    END;
+  END;
+$$ LANGUAGE plpgsql;
+
+
+DO $$
+  BEGIN
+    -- sanity check
+    PERFORM cs_match_v1('{"m": []}'::jsonb);
+
+    BEGIN
+      PERFORM cs_match_v1('{}'::jsonb);
+      RAISE NOTICE 'Missing index. Function call should have failed.';
+      ASSERT false;
+    EXCEPTION
+      WHEN OTHERS THEN
+        ASSERT true;
+    END;
+  END;
+$$ LANGUAGE plpgsql;
+