[GitHub] [arrow] alamb commented on a change in pull request #8397: ARROW-10233: [Rust] Make array_value_to_string available in all Arrow builds

[GitBox <gi...@apache.org>]

alamb commented on a change in pull request #8397:
URL: https://github.com/apache/arrow/pull/8397#discussion_r501717377



##########
File path: rust/arrow/src/util/display.rs
##########
@@ -0,0 +1,135 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! Functions for printing array values, as strings, for debugging
+//! purposes. See the `pretty` crate for additional functions for
+//! record batch pretty printing.
+
+use crate::array;
+use crate::array::{Array, PrimitiveArrayOps};
+use crate::datatypes::{
+    ArrowNativeType, ArrowPrimitiveType, DataType, Int16Type, Int32Type, Int64Type,
+    Int8Type, TimeUnit, UInt16Type, UInt32Type, UInt64Type, UInt8Type,
+};
+
+use array::DictionaryArray;
+
+use crate::error::{ArrowError, Result};
+
+macro_rules! make_string {
+    ($array_type:ty, $column: ident, $row: ident) => {{
+        let array = $column.as_any().downcast_ref::<$array_type>().unwrap();
+
+        let s = if array.is_null($row) {
+            "".to_string()
+        } else {
+            array.value($row).to_string()
+        };
+
+        Ok(s)
+    }};
+}
+
+/// Get the value at the given row in an array as a String.
+///
+/// Note this function is quite inefficient and is unlikely to be
+/// suitable for converting large arrays or record batches.
+pub fn array_value_to_string(column: &array::ArrayRef, row: usize) -> Result<String> {
+    match column.data_type() {
+        DataType::Utf8 => make_string!(array::StringArray, column, row),
+        DataType::Boolean => make_string!(array::BooleanArray, column, row),
+        DataType::Int8 => make_string!(array::Int8Array, column, row),
+        DataType::Int16 => make_string!(array::Int16Array, column, row),
+        DataType::Int32 => make_string!(array::Int32Array, column, row),
+        DataType::Int64 => make_string!(array::Int64Array, column, row),
+        DataType::UInt8 => make_string!(array::UInt8Array, column, row),
+        DataType::UInt16 => make_string!(array::UInt16Array, column, row),
+        DataType::UInt32 => make_string!(array::UInt32Array, column, row),
+        DataType::UInt64 => make_string!(array::UInt64Array, column, row),
+        DataType::Float16 => make_string!(array::Float32Array, column, row),
+        DataType::Float32 => make_string!(array::Float32Array, column, row),
+        DataType::Float64 => make_string!(array::Float64Array, column, row),
+        DataType::Timestamp(unit, _) if *unit == TimeUnit::Second => {
+            make_string!(array::TimestampSecondArray, column, row)
+        }
+        DataType::Timestamp(unit, _) if *unit == TimeUnit::Millisecond => {
+            make_string!(array::TimestampMillisecondArray, column, row)
+        }
+        DataType::Timestamp(unit, _) if *unit == TimeUnit::Microsecond => {
+            make_string!(array::TimestampMicrosecondArray, column, row)
+        }
+        DataType::Timestamp(unit, _) if *unit == TimeUnit::Nanosecond => {
+            make_string!(array::TimestampNanosecondArray, column, row)
+        }
+        DataType::Date32(_) => make_string!(array::Date32Array, column, row),
+        DataType::Date64(_) => make_string!(array::Date64Array, column, row),
+        DataType::Time32(unit) if *unit == TimeUnit::Second => {
+            make_string!(array::Time32SecondArray, column, row)
+        }
+        DataType::Time32(unit) if *unit == TimeUnit::Millisecond => {
+            make_string!(array::Time32MillisecondArray, column, row)
+        }
+        DataType::Time32(unit) if *unit == TimeUnit::Microsecond => {
+            make_string!(array::Time64MicrosecondArray, column, row)
+        }
+        DataType::Time64(unit) if *unit == TimeUnit::Nanosecond => {
+            make_string!(array::Time64NanosecondArray, column, row)
+        }
+        DataType::Dictionary(index_type, _value_type) => match **index_type {
+            DataType::Int8 => dict_array_value_to_string::<Int8Type>(column, row),
+            DataType::Int16 => dict_array_value_to_string::<Int16Type>(column, row),
+            DataType::Int32 => dict_array_value_to_string::<Int32Type>(column, row),
+            DataType::Int64 => dict_array_value_to_string::<Int64Type>(column, row),
+            DataType::UInt8 => dict_array_value_to_string::<UInt8Type>(column, row),
+            DataType::UInt16 => dict_array_value_to_string::<UInt16Type>(column, row),
+            DataType::UInt32 => dict_array_value_to_string::<UInt32Type>(column, row),
+            DataType::UInt64 => dict_array_value_to_string::<UInt64Type>(column, row),
+            _ => Err(ArrowError::InvalidArgumentError(format!(
+                "Pretty printing not supported for {:?} due to index type",
+                column.data_type()
+            ))),
+        },
+        _ => Err(ArrowError::InvalidArgumentError(format!(
+            "Pretty printing not implemented for {:?} type",
+            column.data_type()
+        ))),
+    }
+}
+
+/// Converts the value of the dictionary array at `row` to a String
+fn dict_array_value_to_string<K: ArrowPrimitiveType>(
+    colum: &array::ArrayRef,
+    row: usize,
+) -> Result<String> {
+    let dict_array = colum.as_any().downcast_ref::<DictionaryArray<K>>().unwrap();
+
+    let keys_array = dict_array.keys_array();
+
+    if keys_array.is_null(row) {
+        return Ok(String::from(""));
+    }
+
+    let dict_index = keys_array.value(row).to_usize().ok_or_else(|| {
+        ArrowError::InvalidArgumentError(format!(
+            "Can not convert value {:?} at index {:?} to usize for repl.",

Review comment:
       ```suggestion
               "Can not convert value {:?} at index {:?} to usize for string conversion.",
   ```




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