patch 4.0

src/sql/engine/expr/ob_rt_datum_arith.h

@@ -0,0 +1,118 @@
+/**
+ * Copyright (c) 2021 OceanBase
+ * OceanBase CE is licensed under Mulan PubL v2.
+ * You can use this software according to the terms and conditions of the Mulan PubL v2.
+ * You may obtain a copy of Mulan PubL v2 at:
+ *          http://license.coscl.org.cn/MulanPubL-2.0
+ * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
+ * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
+ * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
+ * See the Mulan PubL v2 for more details.
+ */
+
+#ifndef OCEANBASE_EXPR_OB_RT_DATUM_ARITH_H_
+#define OCEANBASE_EXPR_OB_RT_DATUM_ARITH_H_
+
+#include "sql/resolver/expr/ob_raw_expr.h"
+
+namespace oceanbase
+{
+namespace sql
+{
+
+//
+// Runtime datum arithmetic evaluation.
+//
+// Why need this:
+// ObObj can do runtime arithmetic evaluation by the static interface of arithmetic expressions
+// (e.g.: ObExprMul::calc). ObDatum can not do this, because ObDatum's memory is binding to ObExpr,
+// it always need a ObExpr to do arithmetic evaluation. We must build the needed arithmetic
+// expressions in compile time in static typing engine, see: the `linear_inter_expr_` expression of
+// https://code.aone.alibaba-inc.com/oceanbase/oceanbase/codereview/3278690 commit. It is hard
+// to use,  we need a convenient way to do runtime ObDatum arithmetic evaluation.
+//
+// Usage:
+//
+//  // Calculate: factor * (cur - prev) + prev
+//
+//  ObRTDatumArith arith(exec_context, session);
+//
+//  // prepare runtime datum arithmetic evaluation once
+//  arith.setup_datum_metas(factor_meta, prev_meta, cur_meta);
+//  // arith.ref(0): factor
+//  // arith.ref(1): prev
+//  // arith.ref(2): cur
+//  // the argument of ref() is the index of input
+//  arith.generate(arith.ref(0) * (arith.ref(2) - arith.ref(1)) + arith.ref(1))
+//
+//  // evaluate repeatedly
+//  arith.eval(res_datum, factor_datum, prev_meta, cur_meta);
+//
+class ObRTDatumArith
+{
+public:
+  struct Item
+  {
+    Item() : expr_(NULL), arith_(NULL) {}
+
+    ObRawExpr *expr_;
+    ObRTDatumArith *arith_;
+
+    Item operator+(const Item &r);
+    Item operator-(const Item &r);
+    Item operator*(const Item &r);
+    Item operator/(const Item &r);
+  };
+
+public:
+  ObRTDatumArith(ObExecContext &ctx, ObSQLSessionInfo &session);
+  virtual ~ObRTDatumArith();
+
+  // Setup the input datum metas
+  template <typename ...TS>
+  int setup_datum_metas(TS &...input_meta)
+  {
+    ObDatumMeta metas[] = { input_meta... };
+    return inner_setup_datum_metas(metas, ARRAYSIZEOF(metas));
+  }
+
+  // Get referenced item of %input_idx, which is the index of argument of setup_datum_metas()
+  Item ref(const int64_t input_idx);
+  int generate(const ObRTDatumArith::Item item);
+
+  ObExpr *get_expr() const { return expr_; }
+
+  // Evaluate the input datums' result, set the result's datum ptr to %res.
+  // The %input should be correlate with datum metas in setup_datum_metas().
+  template <typename ...TS>
+  int eval(ObDatum *&res, TS &...input)
+  {
+    const ObDatum *args[] = { &input... };
+    return inner_eval(res, args, ARRAYSIZEOF(args));
+  }
+
+private:
+  Item build_arith_expr(const Item &l, const Item &r, ObItemType op);
+  int inner_setup_datum_metas(const ObDatumMeta *metas, int64_t cnt);
+  int inner_eval(ObDatum *&res, const ObDatum **args, int64_t arg_cnt);
+
+private:
+  common::ObArenaAllocator alloc_;
+
+  ObExecContext &exec_ctx_;
+  ObSQLSessionInfo &session_;
+  ObRawExprFactory factory_;
+  ObExprFrameInfo frame_info_;
+  ObEvalCtx *eval_ctx_;
+  ObExpr *expr_;
+
+  common::ObFixedArray<ObRawExpr *, common::ObIAllocator> raw_cols_;
+  common::ObFixedArray<ObExpr *, common::ObIAllocator> cols_;
+
+  DISABLE_COPY_ASSIGN(ObRTDatumArith);
+};
+
+} // end namespace sql
+} // end namespace oceanbase
+
+#endif // OCEANBASE_EXPR_OB_RT_DAUM_ARITH_H_