SERVER-15639 Correctly handle >1 pred on same text index prefix field

2 files changed, 15 insertions, 2 deletions

diff --git a/src/mongo/db/query/planner_access.cpp b/src/mongo/db/query/planner_access.cpp
index 25ded0425c1..13d978f8d3d 100644
--- a/src/mongo/db/query/planner_access.cpp
+++ b/src/mongo/db/query/planner_access.cpp
@@ -408,11 +408,13 @@ namespace mongo {
                 MatchExpression* child = amExpr->getChild(curChild);
                 IndexTag* ixtag = static_cast<IndexTag*>(child->getTag());
                 invariant(NULL != ixtag);
-                // Only want prefixes.
-                if (ixtag->pos >= prefixEnd) {
+                // Skip this child if it's not part of a prefix, or if we've already assigned a
+                // predicate to this prefix position.
+                if (ixtag->pos >= prefixEnd || prefixExprs[ixtag->pos] != NULL) {
                     ++curChild;
                     continue;
                 }
+                // prefixExprs takes ownership of 'child'.
                 prefixExprs[ixtag->pos] = child;
                 amExpr->getChildVector()->erase(amExpr->getChildVector()->begin() + curChild);
                 // Don't increment curChild.
diff --git a/src/mongo/db/query/query_planner_text_test.cpp b/src/mongo/db/query/query_planner_text_test.cpp
index 2925a2ff7da..13381e5165e 100644
--- a/src/mongo/db/query/query_planner_text_test.cpp
+++ b/src/mongo/db/query/query_planner_text_test.cpp
@@ -466,6 +466,17 @@ namespace {
         assertSolutionExists("{text: {prefix: {a:3}, search: 'foo'}}");
     }
 
+    // SERVER-15639: Test that predicates on index prefix fields which are not assigned to the index
+    // prefix are correctly included in the solution node filter.
+    TEST_F(QueryPlannerTest, TextInsideAndWithCompoundIndexAndMultiplePredsOnIndexPrefix) {
+        params.options = QueryPlannerParams::NO_TABLE_SCAN;
+        addIndex(BSON("a" << 1 << "_fts" << "text" << "_ftsx" << 1));
+        runQuery(fromjson("{$and: [{a: 1}, {a: 2}, {$text: {$search: 'foo'}}]}"));
+
+        assertNumSolutions(1U);
+        assertSolutionExists("{text: {prefix: {a: 1}, search: 'foo', filter: {a: 2}}}");
+    }
+
     // SERVER-13039: Test that we don't generate invalid solutions when the TEXT node
     // is buried beneath a logical node.
     TEST_F(QueryPlannerTest, TextInsideOrBasic) {