Change binary array type from LargeBinaryArray to BinaryArray

[evenyag]

What type of enhancement is this?

Tech debt reduction

What does the enhancement do?

Due to historical reasons, we use LargeBinaryArray for the binary type but StringArray for the string type.

greptimedb/src/datatypes/src/arrow_array.rs

Lines 15 to 18 in b1ef327

	pub type BinaryArray = arrow::array::LargeBinaryArray;
	pub type MutableBinaryArray = arrow::array::LargeBinaryBuilder;
	pub type StringArray = arrow::array::StringArray;
	pub type MutableStringArray = arrow::array::StringBuilder;

As storing and processing are inefficient, I suggest that we could change the default binary array type to BinaryArray.

Implementation challenges

Since the BinaryArray is a type alias, we could change it to LargeBinaryArray and fix the remaining compiler errors.

We need to change the data type mapping to the arrow type.

greptimedb/src/datatypes/src/types/binary_type.rs

Lines 49 to 51 in b1ef327

	fn as_arrow_type(&self) -> ArrowDataType {
	ArrowDataType::LargeBinary
	}

We use our data type and schema while reading the parquet file so we should be able to read old parquet files with binary type columns.

greptimedb/src/mito2/src/sst/parquet/reader.rs

Lines 204 to 208 in b1ef327

	// Computes the field levels.
	let hint = Some(read_format.arrow_schema().fields());
	let field_levels =
	parquet_to_arrow_field_levels(parquet_schema_desc, projection_mask.clone(), hint)
	.context(ReadParquetSnafu { path: &file_path })?;

We might use the old DB to generate a file and read it using the new DB. If this is a breaking change, we should find some places to cast the array to the target type.

Note that we should also modify the helper to cast the binary array correctly.

greptimedb/src/datatypes/src/vectors/helper.rs

Lines 261 to 266 in b1ef327

	ArrowDataType::LargeBinary => Arc::new(BinaryVector::try_from_arrow_array(array)?),
	ArrowDataType::FixedSizeBinary(_) | ArrowDataType::Binary => {
	let array = arrow::compute::cast(array.as_ref(), &ArrowDataType::LargeBinary)
	.context(crate::error::ArrowComputeSnafu)?;
	Arc::new(BinaryVector::try_from_arrow_array(array)?)
	}

I also found a bug while casting the LargeUtf8 type. We are converting a string array into a binary vector......

greptimedb/src/datatypes/src/vectors/helper.rs

Lines 278 to 282 in b1ef327

	ArrowDataType::LargeUtf8 => {
	let array = arrow::compute::cast(array.as_ref(), &ArrowDataType::Utf8)
	.context(crate::error::ArrowComputeSnafu)?;
	Arc::new(BinaryVector::try_from_arrow_array(array)?)
	}