feat: define partition rule trait (#501)

* define partition rule trait.

* address CR.

* add a mock impl.

table_engine/src/partition/rule/mock.rs

@@ -0,0 +1,21 @@
+// Copyright 2022 CeresDB Project Authors. Licensed under Apache-2.0.
+
+//! Mock partition rule
+
+use common_types::row::RowGroup;
+
+use crate::partition::rule::{PartitionFilter, PartitionRule, Result};
+
+pub struct MockRule {
+    pub wanted: usize,
+}
+
+impl PartitionRule for MockRule {
+    fn locate_partitions_for_write(&self, row_group: &RowGroup) -> Result<Vec<usize>> {
+        Ok(vec![self.wanted; row_group.num_rows()])
+    }
+
+    fn locate_partitions_for_read(&self, _filters: &[PartitionFilter]) -> Result<Vec<usize>> {
+        Ok(vec![self.wanted])
+    }
+}

table_engine/src/partition/rule/mod.rs

@@ -0,0 +1,39 @@
+// Copyright 2022 CeresDB Project Authors. Licensed under Apache-2.0.
+
+//! Partition rules
+
+pub mod mock;
+
+use common_types::row::RowGroup;
+use common_util::define_result;
+use datafusion_expr::{Expr, Operator};
+use snafu::Snafu;
+
+#[derive(Debug, Snafu)]
+pub enum Error {}
+
+define_result!(Error);
+
+/// Partition rule locate partition
+pub trait PartitionRule {
+    /// Locate the partition for each row in `row_group`.
+    ///
+    /// Len of returned value should be equal to the one of rows in `row group`.
+    fn locate_partitions_for_write(&self, row_group: &RowGroup) -> Result<Vec<usize>>;
+
+    /// Locate partitions according to `filters`.
+    fn locate_partitions_for_read(&self, filters: &[PartitionFilter]) -> Result<Vec<usize>>;
+}
+
+/// Filter using for partition
+///
+/// Now, it is same as the `BinaryExpr`in datafusion.
+#[allow(dead_code)]
+pub struct PartitionFilter {
+    /// Left-hand side of the expression
+    left: Box<Expr>,
+    /// The comparison operator
+    op: Operator,
+    /// Right-hand side of the expression
+    right: Box<Expr>,
+}