use saturated sum as hit estimate for OR

The upper bound for the hit estimate is the docid limit. The lower
bound for the docid limit is the maximum child estimate.

In the future we probably want a solution where everyone knows the
docid limit from the start, which might also require us to have a
separate way of estimating the document frequency if we want to avoid
ranking score regression.

1 files changed, 16 insertions, 0 deletions

diff --git a/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp b/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp
index eb6e49747a1..802aee8dee0 100644
--- a/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp
+++ b/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp
@@ -1453,4 +1453,20 @@ TEST("require that intermediate cost tier is minimum cost tier of children") {
     EXPECT_EQUAL(bp2->getState().cost_tier(), 2u);
 }
 
+void verify_or_est(const std::vector<Blueprint::HitEstimate> &child_estimates, Blueprint::HitEstimate expect) {
+    OrBlueprint my_or;
+    my_or.setDocIdLimit(32);
+    auto my_est = my_or.combine(child_estimates);
+    EXPECT_EQUAL(my_est.empty, expect.empty);
+    EXPECT_EQUAL(my_est.estHits, expect.estHits);
+}
+
+TEST("require that OR blueprint use saturated sum as estimate") {
+    TEST_DO(verify_or_est({{0, true},{0, true},{0, true}}, {0, true}));
+    TEST_DO(verify_or_est({{0, true},{0, false},{0, true}}, {0, false}));
+    TEST_DO(verify_or_est({{4, false},{6, false},{5, false}}, {15, false}));
+    TEST_DO(verify_or_est({{5, false},{20, false},{10, false}}, {32, false}));
+    TEST_DO(verify_or_est({{100, false},{300, false},{200, false}}, {300, false}));
+}
+
 TEST_MAIN() { TEST_DEBUG("lhs.out", "rhs.out"); TEST_RUN_ALL(); }