add dictionary serialization for csv-writer

src/io/csv/write/serialize.rs

@@ -1,7 +1,7 @@
 use lexical_core::ToLexical;
 
 use crate::temporal_conversions;
-use crate::types::NativeType;
+use crate::types::{Index, NativeType};
 use crate::util::lexical_to_bytes_mut;
 use crate::{
     array::{Array, BinaryArray, BooleanArray, PrimitiveArray, Utf8Array},
@@ -10,6 +10,10 @@ use crate::{
 };
 
 use super::iterator::{BufStreamingIterator, StreamingIterator};
+use crate::array::{DictionaryArray, DictionaryKey, Offset};
+use crate::bitmap::utils::ZipValidity;
+use std::any::Any;
+use std::slice::Iter;
 
 /// Options to serialize logical types to CSV
 #[derive(Debug, PartialEq, Eq, Hash, Clone)]
@@ -265,6 +269,49 @@ pub fn new_serializer<'a>(
                 vec![],
             ))
         }
-        _ => todo!(),
+        DataType::Dictionary(keys_dt, values_dt) => match &**values_dt {
+            DataType::LargeUtf8 => match &**keys_dt {
+                DataType::UInt32 => serialize_utf8_dict::<u32, i64>(array.as_any()),
+                DataType::UInt64 => serialize_utf8_dict::<u64, i64>(array.as_any()),
+                _ => todo!(),
+            },
+            DataType::Utf8 => match &**keys_dt {
+                DataType::UInt32 => serialize_utf8_dict::<u32, i32>(array.as_any()),
+                DataType::UInt64 => serialize_utf8_dict::<u64, i32>(array.as_any()),
+                _ => todo!(),
+            },
+            _ => {
+                panic!("only dictionary with string values are supported by csv writer")
+            }
+        },
+        dt => panic!("data type: {} not supported by csv writer", dt),
     })
 }
+
+/// Helper for serializing a dictonary array. The generic parameters are:
+/// - `K` for the type of the keys of the dictionary
+/// - `O` for the type of the offsets in the Utf8Array: {i32, i64}
+fn serialize_utf8_dict<'a, K: DictionaryKey + Index, O: Offset>(
+    array: &'a dyn Any,
+) -> Box<dyn StreamingIterator<Item = [u8]> + 'a> {
+    let array = array.downcast_ref::<DictionaryArray<K>>().unwrap();
+    let keys = array.keys();
+    let values = array
+        .values()
+        .as_any()
+        .downcast_ref::<Utf8Array<O>>()
+        .unwrap();
+    Box::new(BufStreamingIterator::new(
+        keys.iter(),
+        move |x, buf| {
+            if let Some(x) = x {
+                let i = Index::to_usize(x);
+                if !values.is_null(i) {
+                    let val = values.value(i);
+                    buf.extend_from_slice(val.as_bytes());
+                }
+            }
+        },
+        vec![],
+    ))
+}

tests/it/io/csv/write.rs

@@ -15,6 +15,11 @@ fn data() -> RecordBatch {
         Field::new("c4", DataType::Boolean, true),
         Field::new("c5", DataType::Timestamp(TimeUnit::Millisecond, None), true),
         Field::new("c6", DataType::Time32(TimeUnit::Second), false),
+        Field::new(
+            "c7",
+            DataType::Dictionary(Box::new(DataType::UInt32), Box::new(DataType::Utf8)),
+            false,
+        ),
     ]);
 
     let c1 = Utf8Array::<i32>::from_slice([
@@ -29,6 +34,8 @@ fn data() -> RecordBatch {
         .to(DataType::Timestamp(TimeUnit::Millisecond, None));
     let c6 = PrimitiveArray::<i32>::from_slice(&[1234, 24680, 85563])
         .to(DataType::Time32(TimeUnit::Second));
+    let keys = UInt32Array::from_slice(&[2, 0, 1]);
+    let c7 = DictionaryArray::from_data(keys, Arc::new(c1.clone()));
 
     RecordBatch::try_new(
         Arc::new(schema),
@@ -39,6 +46,7 @@ fn data() -> RecordBatch {
             Arc::new(c4),
             Arc::new(c5),
             Arc::new(c6),
+            Arc::new(c7),
         ],
     )
     .unwrap()
@@ -61,13 +69,13 @@ fn write_csv() -> Result<()> {
     // check
     let buffer = writer.into_inner().unwrap().into_inner();
     assert_eq!(
-        r#"c1,c2,c3,c4,c5,c6
-Lorem ipsum dolor sit amet,123.564532,3,true,,00:20:34
-consectetur adipiscing elit,,2,false,2019-04-18T10:54:47.378000000,06:51:20
-sed do eiusmod tempor,-556132.25,1,,2019-04-18T02:45:55.555000000,23:46:03
-Lorem ipsum dolor sit amet,123.564532,3,true,,00:20:34
-consectetur adipiscing elit,,2,false,2019-04-18T10:54:47.378000000,06:51:20
-sed do eiusmod tempor,-556132.25,1,,2019-04-18T02:45:55.555000000,23:46:03
+        r#"c1,c2,c3,c4,c5,c6,c7
+Lorem ipsum dolor sit amet,123.564532,3,true,,00:20:34,sed do eiusmod tempor
+consectetur adipiscing elit,,2,false,2019-04-18T10:54:47.378000000,06:51:20,Lorem ipsum dolor sit amet
+sed do eiusmod tempor,-556132.25,1,,2019-04-18T02:45:55.555000000,23:46:03,consectetur adipiscing elit
+Lorem ipsum dolor sit amet,123.564532,3,true,,00:20:34,sed do eiusmod tempor
+consectetur adipiscing elit,,2,false,2019-04-18T10:54:47.378000000,06:51:20,Lorem ipsum dolor sit amet
+sed do eiusmod tempor,-556132.25,1,,2019-04-18T02:45:55.555000000,23:46:03,consectetur adipiscing elit
 "#
         .to_string(),
         String::from_utf8(buffer).unwrap(),
@@ -92,9 +100,9 @@ fn write_csv_custom_options() -> Result<()> {
     // check
     let buffer = writer.into_inner().unwrap().into_inner();
     assert_eq!(
-        r#"Lorem ipsum dolor sit amet|123.564532|3|true||12:20:34 AM
-consectetur adipiscing elit||2|false|2019-04-18T10:54:47.378000000|06:51:20 AM
-sed do eiusmod tempor|-556132.25|1||2019-04-18T02:45:55.555000000|11:46:03 PM
+        r#"Lorem ipsum dolor sit amet|123.564532|3|true||12:20:34 AM|sed do eiusmod tempor
+consectetur adipiscing elit||2|false|2019-04-18T10:54:47.378000000|06:51:20 AM|Lorem ipsum dolor sit amet
+sed do eiusmod tempor|-556132.25|1||2019-04-18T02:45:55.555000000|11:46:03 PM|consectetur adipiscing elit
 "#
         .to_string(),
         String::from_utf8(buffer).unwrap(),