From e51899314dbf77a2a40a2607cb797ee4af532171 Mon Sep 17 00:00:00 2001
From: Eric Fischer <enf@pobox.com>
Date: Fri, 5 Apr 2019 15:10:39 -0700
Subject: [PATCH] Don't run shell filters if the current zoom is below the
 minzoom

---
 tile.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tile.cpp b/tile.cpp
index 72672f7..6e76c50 100644
--- a/tile.cpp
+++ b/tile.cpp
@@ -1786,6 +1786,11 @@ long long write_tile(FILE *geoms, std::atomic<long long> *geompos_in, char *meta
 		FILE *prefilter_read_fp = NULL;
 		json_pull *prefilter_jp = NULL;
 
+		if (z < minzoom) {
+			prefilter = NULL;
+			postfilter = NULL;
+		}
+
 		if (prefilter != NULL) {
 			setup_filter(prefilter, &prefilter_write, &prefilter_read, &prefilter_pid, z, tx, ty);
 			prefilter_fp = fdopen(prefilter_write, "w");