basic concepts used to replace ranking expressions with intrinsic operations

5 files changed, 149 insertions, 0 deletions

diff --git a/searchlib/src/vespa/searchlib/features/rankingexpression/CMakeLists.txt b/searchlib/src/vespa/searchlib/features/rankingexpression/CMakeLists.txt
index deb33fead55..3ca8c36398c 100644
--- a/searchlib/src/vespa/searchlib/features/rankingexpression/CMakeLists.txt
+++ b/searchlib/src/vespa/searchlib/features/rankingexpression/CMakeLists.txt
@@ -1,6 +1,8 @@
 # Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 vespa_add_library(searchlib_features_rankingexpression OBJECT
     SOURCES
+    expression_replacer.cpp
     feature_name_extractor.cpp
+    intrinsic_expression.cpp
     DEPENDS
 )
diff --git a/searchlib/src/vespa/searchlib/features/rankingexpression/expression_replacer.cpp b/searchlib/src/vespa/searchlib/features/rankingexpression/expression_replacer.cpp
new file mode 100644
index 00000000000..7de5503582a
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/features/rankingexpression/expression_replacer.cpp
@@ -0,0 +1,50 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "expression_replacer.h"
+
+namespace search::features::rankingexpression {
+
+ExpressionReplacer::~ExpressionReplacer()
+{
+}
+
+//-----------------------------------------------------------------------------
+
+IntrinsicExpression::UP
+NullExpressionReplacer::maybe_replace(const vespalib::eval::Function &,
+                                      const search::fef::IIndexEnvironment &) const
+{
+    return IntrinsicExpression::UP(nullptr);
+}
+
+NullExpressionReplacer::~NullExpressionReplacer()
+{
+}
+
+//-----------------------------------------------------------------------------
+
+ListExpressionReplacer::ListExpressionReplacer() = default;
+
+void
+ListExpressionReplacer::add(ExpressionReplacer::UP replacer)
+{
+    _list.push_back(std::move(replacer));
+}
+
+IntrinsicExpression::UP
+ListExpressionReplacer::maybe_replace(const vespalib::eval::Function &function,
+                                      const search::fef::IIndexEnvironment &env) const
+{
+    for (const auto &item: _list) {
+        if (auto result = item.get()->maybe_replace(function, env)) {
+            return result;
+        }
+    }
+    return IntrinsicExpression::UP(nullptr);
+}
+
+ListExpressionReplacer::~ListExpressionReplacer()
+{
+}
+
+} // namespace search::features::rankingexpression
diff --git a/searchlib/src/vespa/searchlib/features/rankingexpression/expression_replacer.h b/searchlib/src/vespa/searchlib/features/rankingexpression/expression_replacer.h
new file mode 100644
index 00000000000..2a2d9f24439
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/features/rankingexpression/expression_replacer.h
@@ -0,0 +1,54 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <memory>
+#include <vector>
+#include "intrinsic_expression.h"
+
+namespace vespalib::eval { class Function; }
+namespace search::fef { class IIndexEnvironment; }
+
+namespace search::features::rankingexpression {
+
+/**
+ * Interface used to replace the calculation of a ranking expression
+ * (including calculating all its inputs) with a single intrinsic
+ * operation directly producing the final result without exposing
+ * intermediate results.
+ **/
+struct ExpressionReplacer {
+    using UP = std::unique_ptr<ExpressionReplacer>;
+    using SP = std::shared_ptr<ExpressionReplacer>;
+    virtual IntrinsicExpression::UP maybe_replace(const vespalib::eval::Function &function,
+                                                  const search::fef::IIndexEnvironment &env) const = 0;
+    virtual ~ExpressionReplacer();
+};
+
+/**
+ * Expression Replacer never replacing anything.
+ **/
+struct NullExpressionReplacer : public ExpressionReplacer {
+    IntrinsicExpression::UP maybe_replace(const vespalib::eval::Function &function,
+                                          const search::fef::IIndexEnvironment &env) const override;
+    ~NullExpressionReplacer();
+};
+
+/**
+ * Expression Replacer that keeps a list of expression replacers and
+ * forwards the replace calls to each of them in order until the
+ * expression has been replaced or all of them have been tried.
+ **/
+class ListExpressionReplacer : public ExpressionReplacer
+{
+private:
+    std::vector<ExpressionReplacer::UP> _list;
+public:
+    ListExpressionReplacer();
+    void add(ExpressionReplacer::UP replacer);
+    IntrinsicExpression::UP maybe_replace(const vespalib::eval::Function &function,
+                                          const search::fef::IIndexEnvironment &env) const override;
+    ~ListExpressionReplacer();
+};
+
+} // namespace search::features::rankingexpression
diff --git a/searchlib/src/vespa/searchlib/features/rankingexpression/intrinsic_expression.cpp b/searchlib/src/vespa/searchlib/features/rankingexpression/intrinsic_expression.cpp
new file mode 100644
index 00000000000..cceefa58104
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/features/rankingexpression/intrinsic_expression.cpp
@@ -0,0 +1,11 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "intrinsic_expression.h"
+
+namespace search::features::rankingexpression {
+
+IntrinsicExpression::~IntrinsicExpression()
+{
+}
+
+} // namespace search::features::rankingexpression
diff --git a/searchlib/src/vespa/searchlib/features/rankingexpression/intrinsic_expression.h b/searchlib/src/vespa/searchlib/features/rankingexpression/intrinsic_expression.h
new file mode 100644
index 00000000000..3180b828c79
--- /dev/null
+++ b/searchlib/src/vespa/searchlib/features/rankingexpression/intrinsic_expression.h
@@ -0,0 +1,32 @@
+// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <memory>
+
+namespace vespalib { class Stash; }
+
+namespace search::fef {
+class FeatureType;
+class FeatureExecutor;
+class IQueryEnvironment;
+}
+
+namespace search::features::rankingexpression {
+
+/**
+ * Interface representing an intrinsic expression replacing the
+ * calculation of a ranking expression and its inputs.
+ **/
+struct IntrinsicExpression {
+    using FeatureType = search::fef::FeatureType;
+    using FeatureExecutor = search::fef::FeatureExecutor;
+    using QueryEnv = search::fef::IQueryEnvironment;
+    using UP = std::unique_ptr<IntrinsicExpression>;
+    virtual FeatureType result_type() const = 0;
+    virtual FeatureExecutor &create_executor(const QueryEnv &queryEnv,
+                                             vespalib::Stash &stash) const = 0;
+    virtual ~IntrinsicExpression();
+};
+
+} // namespace search::features::rankingexpression