fret(type): add support for Decimal type in database

The database schema has been updated to support the Decimal data type. This includes casting from and to Decimal type in the DataValue structure, creating a new Decimal field in both LogicalType and DataValue structures, and adding appropriate match arms in the from_sqlparser_data_type and can_implicit_cast functions. A new error type for when an attempted conversion from Decimal fails have also been implemented. The round_dp_with_strategy method is used to provide flexibility with scale modification and rounding strategy when casting to Decimal type. Tests for the new functionality have been added as well.

Cargo.toml

@@ -32,6 +32,7 @@ comfy-table = "7.0.1"
 bytes = "*"
 kip_db = "0.1.2-alpha.15"
 async-recursion = "1.0.5"
+rust_decimal = "1"
 
 [dev-dependencies]
 tokio-test = "0.4.2"

src/db.rs

@@ -186,6 +186,9 @@ mod test {
         let _ = kipsql.run("create table t2 (c int primary key, d int unsigned null, e datetime)").await?;
         let _ = kipsql.run("insert into t1 (a, b, k) values (-99, 1, 1), (-1, 2, 2), (5, 2, 2)").await?;
         let _ = kipsql.run("insert into t2 (d, c, e) values (2, 1, '2021-05-20 21:00:00'), (3, 4, '2023-09-10 00:00:00')").await?;
+        let _ = kipsql.run("create table t3 (a int primary key, b decimal(4,2))").await?;
+        let _ = kipsql.run("insert into t3 (a, b) values (1, 1111), (2, 2.01), (3, 3.00)").await?;
+        let _ = kipsql.run("insert into t3 (a, b) values (4, 4444), (5, 5222), (6, 1.00)").await?;
 
         println!("full t1:");
         let tuples_full_fields_t1 = kipsql.run("select * from t1").await?;
@@ -305,6 +308,10 @@ mod test {
         let tuples_show_tables = kipsql.run("show tables").await?;
         println!("{}", create_table(&tuples_show_tables));
 
+        println!("decimal:");
+        let tuples_decimal = kipsql.run("select * from t3").await?;
+        println!("{}", create_table(&tuples_decimal));
+
         Ok(())
     }
 }

src/expression/mod.rs

@@ -1,5 +1,5 @@
 use std::fmt;
-use std::fmt::Formatter;
+use std::fmt::{Debug, Formatter};
 use std::sync::Arc;
 use itertools::Itertools;
 

src/storage/table_codec.rs

@@ -146,6 +146,7 @@ mod tests {
     use std::ops::Bound;
     use std::sync::Arc;
     use itertools::Itertools;
+    use rust_decimal::Decimal;
     use crate::catalog::{ColumnCatalog, ColumnDesc, TableCatalog};
     use crate::storage::table_codec::{COLUMNS_ID_LEN, TableCodec};
     use crate::types::errors::TypeError;
@@ -159,7 +160,12 @@ mod tests {
                 "c1".into(),
                 false,
                 ColumnDesc::new(LogicalType::Integer, true)
-            )
+            ),
+            ColumnCatalog::new(
+                "c2".into(),
+                false,
+                ColumnDesc::new(LogicalType::Decimal(None,None), false)
+            ),
         ];
         let table_catalog = TableCatalog::new(Arc::new("t1".to_string()), columns).unwrap();
         let codec = TableCodec { table: table_catalog.clone() };
@@ -175,6 +181,7 @@ mod tests {
             columns: table_catalog.all_columns(),
             values: vec![
                 Arc::new(DataValue::Int32(Some(0))),
+                Arc::new(DataValue::Decimal(Some(Decimal::new(1, 0)))),
             ]
         };
 

src/types/errors.rs

@@ -46,4 +46,10 @@ pub enum TypeError {
         #[from]
         ParseError,
     ),
+    #[error("try from decimal")]
+    TryFromDecimal(
+        #[source]
+        #[from]
+        rust_decimal::Error,
+    ),
 }

src/types/mod.rs

@@ -7,6 +7,7 @@ use std::sync::atomic::Ordering::{Acquire, Release};
 use serde::{Deserialize, Serialize};
 
 use integer_encoding::FixedInt;
+use sqlparser::ast::ExactNumberInfo;
 use strum_macros::AsRefStr;
 
 use crate::types::errors::TypeError;
@@ -57,6 +58,8 @@ pub enum LogicalType {
     Varchar(Option<u32>),
     Date,
     DateTime,
+    // decimal (precision, scale)
+    Decimal(Option<u8>, Option<u8>),
 }
 
 impl LogicalType {
@@ -75,8 +78,9 @@ impl LogicalType {
             LogicalType::UBigint => Some(8),
             LogicalType::Float => Some(4),
             LogicalType::Double => Some(8),
-            /// Note: The non-fixed length type's raw_len is None
+            /// Note: The non-fixed length type's raw_len is None e.g. Varchar and Decimal
             LogicalType::Varchar(_)=>None,
+            LogicalType::Decimal(_, _) =>None,
             LogicalType::Date => Some(4),
             LogicalType::DateTime => Some(8),
         }
@@ -269,6 +273,7 @@ impl LogicalType {
             LogicalType::Varchar(_) => false,
             LogicalType::Date => matches!(to, LogicalType::DateTime | LogicalType::Varchar(_)),
             LogicalType::DateTime => matches!(to, LogicalType::Date | LogicalType::Varchar(_)),
+            LogicalType::Decimal(_, _) => false,
         }
     }
 }
@@ -296,6 +301,13 @@ impl TryFrom<sqlparser::ast::DataType> for LogicalType {
             sqlparser::ast::DataType::UnsignedBigInt(_) => Ok(LogicalType::UBigint),
             sqlparser::ast::DataType::Boolean => Ok(LogicalType::Boolean),
             sqlparser::ast::DataType::Datetime(_) => Ok(LogicalType::DateTime),
+            sqlparser::ast::DataType::Decimal(info) =>  match info {
+                    ExactNumberInfo::None => Ok(Self::Decimal(None, None)),
+                    ExactNumberInfo::Precision(p) => Ok(Self::Decimal(Some(p as u8), None)),
+                    ExactNumberInfo::PrecisionAndScale(p, s) => {
+                        Ok(Self::Decimal(Some(p as u8), Some(s as u8)))
+                    }
+            },
             other => Err(TypeError::NotImplementedSqlparserDataType(
                 other.to_string(),
             )),
@@ -313,7 +325,7 @@ impl std::fmt::Display for LogicalType {
 mod test {
     use std::sync::atomic::Ordering::Release;
 
-    use crate::types::{IdGenerator, ID_BUF, LogicalType};
+    use crate::types::{IdGenerator, ID_BUF};
 
     /// Tips: 由于IdGenerator为static全局性质生成的id，因此需要单独测试避免其他测试方法干扰
     #[test]