api: fix proof/root query to be more specific (#67)

Author: worm-emoji

api/migrations/migrations.go

@@ -85,4 +85,23 @@ var Migrations = []migrate.Migration{
 		SET NOT NULL;
 		`,
 	},
+	{
+		Name: "2022-08-31.0.root-func-index.sql",
+		SQL: `
+		CREATE OR REPLACE FUNCTION proofs_array (data jsonb)
+			RETURNS text[]
+			AS $CODE$
+		BEGIN
+			RETURN ARRAY (
+				SELECT
+					jsonb_array_elements(data) ->> 'proof');
+		END
+		$CODE$
+		LANGUAGE plpgsql
+		IMMUTABLE;
+
+		CREATE INDEX proofs_arr_idx ON trees USING GIN ((proofs_array(proofs)));
+		DROP INDEX "trees_proofs_idx";
+	`,
+	},
 }

api/root.go

@@ -45,7 +45,7 @@ func (s *Server) GetRoot(w http.ResponseWriter, r *http.Request) {
 	const q = `
 		SELECT root
 		FROM trees
-		WHERE proofs @> $1
+		WHERE proofs_array(proofs) @> proofs_array($1)
 		LIMIT 1
 	`