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src/sql/engine/basic/ob_count_op.cpp

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+/**
+ * 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.
+ */
+
+#define USING_LOG_PREFIX SQL_ENG
+
+#include "ob_count_op.h"
+#include "sql/engine/ob_physical_plan.h"
+#include "sql/engine/ob_exec_context.h"
+
+namespace oceanbase {
+namespace sql {
+
+ObCountSpec::ObCountSpec(ObIAllocator& alloc, const ObPhyOperatorType type)
+    : ObOpSpec(alloc, type), rownum_limit_(NULL), anti_monotone_filters_(alloc)
+
+{}
+
+OB_SERIALIZE_MEMBER((ObCountSpec, ObOpSpec), rownum_limit_, anti_monotone_filters_);
+
+ObCountOp::ObCountOp(ObExecContext& exec_ctx, const ObOpSpec& spec, ObOpInput* input)
+    : ObOperator(exec_ctx, spec, input)
+{
+  reset_default();
+}
+
+void ObCountOp::reset_default()
+{
+  cur_rownum_ = 0;
+  rownum_limit_ = INT64_MAX;
+}
+
+int ObCountOp::inner_open()
+{
+  int ret = OB_SUCCESS;
+  if (OB_ISNULL(child_)) {
+    ret = OB_ERR_UNEXPECTED;
+    LOG_WARN("count operator has no child", K(ret));
+  } else if (OB_FAIL(get_rownum_limit())) {
+    LOG_WARN("get rownum limit failed", K(ret));
+  }
+  return ret;
+}
+
+int ObCountOp::get_rownum_limit()
+{
+  int ret = OB_SUCCESS;
+  ObExpr* expr = MY_SPEC.rownum_limit_;
+  if (NULL != expr) {
+    ObDatum* datum = NULL;
+    if (OB_FAIL(expr->eval(eval_ctx_, datum))) {
+      LOG_WARN("limit expr evaluate failed", K(ret));
+    } else {
+      if (datum->null_) {
+        rownum_limit_ = 0;
+      } else {
+        OB_ASSERT(ob_is_int_tc(expr->datum_meta_.type_));
+        rownum_limit_ = *datum->int_;
+      }
+    }
+  }
+  return ret;
+}
+
+int ObCountOp::rescan()
+{
+  int ret = OB_SUCCESS;
+
+  if (OB_FAIL(ObOperator::rescan())) {
+    if (OB_ITER_END != ret) {
+      LOG_WARN("operator rescan fail", K(ret));
+    }
+  } else {
+    reset_default();
+    OZ(get_rownum_limit());
+  }
+  return ret;
+}
+
+int ObCountOp::switch_iterator()
+{
+  int ret = OB_SUCCESS;
+  if (OB_FAIL(ObOperator::switch_iterator())) {
+    if (OB_ITER_END != ret) {
+      LOG_WARN("operator switch iterator fail", K(ret));
+    }
+  } else {
+    reset_default();
+    OZ(get_rownum_limit());
+  }
+  return ret;
+}
+
+int ObCountOp::get_next_row()
+{
+  int ret = OB_SUCCESS;
+  if (cur_rownum_ >= rownum_limit_) {
+    ret = OB_ITER_END;
+  } else {
+    cur_rownum_ += 1;
+    if (OB_FAIL(ObOperator::get_next_row())) {
+      cur_rownum_ -= 1;
+      if (OB_ITER_END != ret) {
+        LOG_WARN("operator get next row failed", K(ret));
+      }
+    }
+  }
+  return ret;
+}
+
+int ObCountOp::inner_get_next_row()
+{
+  int ret = OB_SUCCESS;
+  if (OB_FAIL(child_->get_next_row())) {
+    if (OB_ITER_END != ret) {
+      LOG_WARN("get row from child failed", K(ret));
+    }
+  } else {
+    clear_evaluated_flag();
+    if (!MY_SPEC.anti_monotone_filters_.empty()) {
+      bool filtered = false;
+      if (OB_FAIL(filter(MY_SPEC.anti_monotone_filters_, filtered))) {
+        LOG_WARN("filter row failed", K(ret));
+      } else if (filtered) {
+        // Set rownum limit to zero make it return OB_ITER_END directly on next call.
+        rownum_limit_ = 0;
+        ret = OB_ITER_END;
+      }
+    }
+  }
+  return ret;
+}
+
+}  // end namespace sql
+}  // end namespace oceanbase