SERVER-14731 print more debug info when plan_cache_ties.js fails

(cherry picked from commit 791e2e00806449a01e7dec4d9b969392e183f393)

1 files changed, 36 insertions, 4 deletions

diff --git a/jstests/core/plan_cache_ties.js b/jstests/core/plan_cache_ties.js
index edb16c0b18b..70c69925a91 100644
--- a/jstests/core/plan_cache_ties.js
+++ b/jstests/core/plan_cache_ties.js
@@ -3,6 +3,23 @@
 var t = db.jstests_plan_cache_ties;
 t.drop();
 
+var shapes;
+
+// Generates debug info. Used in the case of test failure.
+function dumpPlanCache(shapes) {
+    var outstr = '';
+
+    // For each shape in the cache, get the plan cache entry.
+    for (var i = 0; i < shapes.length; i++) {
+        var shape = shapes[i];
+        var cache = t.getPlanCache();
+        var plans = cache.getPlansByQuery(shape.query, shape.projection, shape.sort);
+        outstr += ('getPlansByQuery() for shape ' + i + ' = ' + tojson(plans) + '\n');
+    }
+
+    return outstr;
+}
+
 // Utility function to list query shapes in cache.
 function getShapes(collection) {
     if (collection == undefined) {
@@ -23,17 +40,29 @@ for (var i = 0; i < 200; i++) {
 }
 t.save({a: 2, b: 2});
 
+// Do a full collection scan to pull the whole collection into memory.
+assert.eq(201, t.find().itcount(), 'unexpected number of docs in collection');
+
 // A query with zero results that does not hit EOF should not be cached.
 assert.eq(0, t.find({c: 0}).itcount(), 'unexpected count');
-assert.eq(0, getShapes().length, 'unexpected number of query shapes in plan cache');
+shapes = getShapes();
+assert.eq(0, shapes.length,
+          'unexpected number of query shapes in plan cache\n'
+          + dumpPlanCache(shapes));
 
 // A query that hits EOF but still results in a tie should not be cached.
 assert.eq(0, t.find({a: 3, b: 3}).itcount(), 'unexpected count');
-assert.eq(0, getShapes().length, 'unexpected number of query shapes in plan cache');
+shapes = getShapes()
+assert.eq(0, shapes.length,
+          'unexpected number of query shapes in plan cache\n'
+          + dumpPlanCache(shapes));
 
 // A query that returns results but leads to a tie should not be cached.
 assert.eq(1, t.find({a: 2, b: 2}).itcount(), 'unexpected count');
-assert.eq(0, getShapes().length, 'unexpected number of query shapes in plan cache');
+shapes = getShapes();
+assert.eq(0, shapes.length,
+          'unexpected number of query shapes in plan cache\n'
+          + dumpPlanCache(shapes));
 
 // With a new index and tweaked data, we deliver a new query that should not tie. Check that
 // this one gets cached.
@@ -44,4 +73,7 @@ for (var i = 0; i < 3; i++) {
 }
 
 assert.eq(1, t.find({a: 2, b: 2}).itcount(), 'unexpected count');
-assert.eq(1, getShapes().length, 'unexpected number of query shapes in plan cache');
+shapes = getShapes();
+assert.eq(1, shapes.length,
+          'unexpected number of query shapes in plan cache\n'
+          + dumpPlanCache(shapes));