From ef3e099a424694e6247252a40c7b3be343f3cebd Mon Sep 17 00:00:00 2001
From: Sebastian Harl <sh@tokkee.org>
Date: Tue, 30 Sep 2014 07:40:52 -0700
Subject: [PATCH] When querying services/metrics skip hosts without such
 children.

This takes into account any filters and, thus, might mean that filters have to
be evaluated multiple times: once for determining if there are any children
and then again while serializing the data. This is because filtering happens
during serialization at which point it's too late to skip a host.
---
 src/core/store.c              | 37 +++++++++++++++++++++++++++++++++++
 src/frontend/query.c          |  6 ++++--
 src/include/core/store.h      | 11 ++++++++---
 t/integration/simple_query.sh |  1 -
 4 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/src/core/store.c b/src/core/store.c
index e14f27c..8cb30ef 100644
--- a/src/core/store.c
+++ b/src/core/store.c
@@ -928,6 +928,10 @@ sdb_store_host_tojson(sdb_store_obj_t *h, sdb_strbuf_t *buf,
 	if ((! h) || (h->type != SDB_HOST) || (! buf))
 		return -1;
 
+	/* This function ignores SKIP_EMPTY flags given that the current
+	 * implementation sucks and it's nut currently used when calling this
+	 * function directly. */
+
 	sdb_strbuf_append(buf, "{\"name\": \"%s\", ", SDB_OBJ(host)->name);
 	store_common_tojson(h, buf);
 
@@ -950,6 +954,26 @@ sdb_store_host_tojson(sdb_store_obj_t *h, sdb_strbuf_t *buf,
 	return 0;
 } /* sdb_store_host_tojson */
 
+static _Bool
+has_children(sdb_avltree_t *tree, sdb_store_matcher_t *filter)
+{
+	sdb_avltree_iter_t *iter;
+
+	if (! filter)
+		return sdb_avltree_size(tree) > 0;
+
+	iter = sdb_avltree_get_iter(tree);
+	while (sdb_avltree_iter_has_next(iter)) {
+		sdb_store_obj_t *sobj = STORE_OBJ(sdb_avltree_iter_get_next(iter));
+		if (sdb_store_matcher_matches(filter, sobj, NULL)) {
+			sdb_avltree_iter_destroy(iter);
+			return 1;
+		}
+	}
+	sdb_avltree_iter_destroy(iter);
+	return 0;
+} /* has_children */
+
 int
 sdb_store_tojson(sdb_strbuf_t *buf, sdb_store_matcher_t *filter, int flags)
 {
@@ -979,6 +1003,19 @@ sdb_store_tojson(sdb_strbuf_t *buf, sdb_store_matcher_t *filter, int flags)
 		if (filter && (! sdb_store_matcher_matches(filter, host, NULL)))
 			continue;
 
+		/*
+		 * XXX: This approach sucks but it's the best we can do at the moment.
+		 * In the future, all store lookups should be split into multiple
+		 * steps instead: first, retrieve all relevant objects and apply all
+		 * pre-processing operations and then format it for the wire.
+		 */
+		if ((flags & SDB_SKIP_EMPTY_SERVICES)
+				&& (! has_children(HOST(host)->services, filter)))
+			continue;
+		if ((flags & SDB_SKIP_EMPTY_METRICS)
+				&& (! has_children(HOST(host)->metrics, filter)))
+			continue;
+
 		if (sdb_strbuf_len(buf) > len)
 			sdb_strbuf_append(buf, ",");
 		len = sdb_strbuf_len(buf);
diff --git a/src/frontend/query.c b/src/frontend/query.c
index 0ee734c..1751ba5 100644
--- a/src/frontend/query.c
+++ b/src/frontend/query.c
@@ -271,9 +271,11 @@ sdb_fe_exec_list(sdb_conn_t *conn, int type, sdb_store_matcher_t *filter)
 	if (type == SDB_HOST)
 		flags = SDB_SKIP_ALL;
 	else if (type == SDB_SERVICE)
-		flags = SDB_SKIP_ALL & (~SDB_SKIP_SERVICES);
+		flags = (SDB_SKIP_ALL & (~SDB_SKIP_SERVICES))
+			| SDB_SKIP_EMPTY_SERVICES;
 	else if (type == SDB_METRIC)
-		flags = SDB_SKIP_ALL & (~SDB_SKIP_METRICS);
+		flags = (SDB_SKIP_ALL & (~SDB_SKIP_METRICS))
+			| SDB_SKIP_EMPTY_METRICS;
 	else {
 		sdb_log(SDB_LOG_ERR, "frontend: Invalid object type %d "
 				"for LIST command", type);
diff --git a/src/include/core/store.h b/src/include/core/store.h
index fa974bb..d5a7694 100644
--- a/src/include/core/store.h
+++ b/src/include/core/store.h
@@ -518,8 +518,9 @@ sdb_store_scan(sdb_store_matcher_t *m, sdb_store_matcher_t *filter,
 /*
  * Flags for serialization functions.
  *
- * By default, the full object will be included in the serialized output. When
- * specifying any of the flags, the respective information will be left out.
+ * By default, the full host object will be included in the serialized output.
+ * When specifying any of the flags, the respective information will be left
+ * out. The SKIP_EMPTY flags may be used to skip host objects entirely.
  */
 enum {
 	SDB_SKIP_ATTRIBUTES         = 1 << 0,
@@ -527,7 +528,11 @@ enum {
 	SDB_SKIP_METRICS            = 1 << 2,
 	SDB_SKIP_SERVICE_ATTRIBUTES = 1 << 3,
 
-	SDB_SKIP_ALL                = 0xffff,
+	SDB_SKIP_ALL                = (1 << 8) - 1,
+
+	/* skip hosts if they do not reference any services/metrics */
+	SDB_SKIP_EMPTY_SERVICES     = 1 << 8,
+	SDB_SKIP_EMPTY_METRICS      = 1 << 9,
 };
 
 /*
diff --git a/t/integration/simple_query.sh b/t/integration/simple_query.sh
index 900db90..b639443 100755
--- a/t/integration/simple_query.sh
+++ b/t/integration/simple_query.sh
@@ -75,7 +75,6 @@ echo "$output" \
 	| grep -F '"host1.example.com"' \
 	| grep -F '"host2.example.com"' \
 	| grep -F '"localhost"' \
-	| grep -F '"other.host.name"' \
 	| grep -F '"some.host.name"' \
 	| grep -F '"mock service"' \
 	| grep -F '"other service"' \
-- 
2.30.2