Abhisheklearn12 commented on code in PR #9379: URL: https://github.com/apache/arrow-rs/pull/9379#discussion_r2789472604
########## arrow-json/src/reader/run_end_array.rs: ########## @@ -0,0 +1,150 @@ +// 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. + +use crate::reader::tape::Tape; +use crate::reader::{ArrayDecoder, DecoderContext}; +use arrow_array::Array; +use arrow_data::transform::MutableArrayData; +use arrow_data::{ArrayData, ArrayDataBuilder}; +use arrow_schema::{ArrowError, DataType}; + +pub struct RunEndEncodedArrayDecoder { + data_type: DataType, + decoder: Box<dyn ArrayDecoder>, +} + +impl RunEndEncodedArrayDecoder { + pub fn new( + ctx: &DecoderContext, + data_type: &DataType, + is_nullable: bool, + ) -> Result<Self, ArrowError> { + let values_field = match data_type { + DataType::RunEndEncoded(_, v) => v, + _ => unreachable!(), + }; + let decoder = ctx.make_decoder( + values_field.data_type(), + values_field.is_nullable() || is_nullable, + )?; + + Ok(Self { + data_type: data_type.clone(), + decoder, + }) + } +} + +impl ArrayDecoder for RunEndEncodedArrayDecoder { + fn decode(&mut self, tape: &Tape<'_>, pos: &[u32]) -> Result<ArrayData, ArrowError> { + let run_ends_type = match &self.data_type { + DataType::RunEndEncoded(r, _) => r.data_type(), + _ => unreachable!(), + }; + + let len = pos.len(); + if len == 0 { + let empty_run_ends = new_empty_run_ends(run_ends_type); Review Comment: Yeah, `new_empty_array` handles this cleanly. The decode call was there to get a typed empty values array but that's redundant when `new_empty_array` already constructs the full REE structure. So, will simplify it. ########## arrow-json/src/reader/run_end_array.rs: ########## @@ -0,0 +1,150 @@ +// 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. + +use crate::reader::tape::Tape; +use crate::reader::{ArrayDecoder, DecoderContext}; +use arrow_array::Array; +use arrow_data::transform::MutableArrayData; +use arrow_data::{ArrayData, ArrayDataBuilder}; +use arrow_schema::{ArrowError, DataType}; + +pub struct RunEndEncodedArrayDecoder { + data_type: DataType, + decoder: Box<dyn ArrayDecoder>, +} + +impl RunEndEncodedArrayDecoder { + pub fn new( + ctx: &DecoderContext, + data_type: &DataType, + is_nullable: bool, + ) -> Result<Self, ArrowError> { + let values_field = match data_type { + DataType::RunEndEncoded(_, v) => v, + _ => unreachable!(), + }; + let decoder = ctx.make_decoder( + values_field.data_type(), + values_field.is_nullable() || is_nullable, + )?; + + Ok(Self { + data_type: data_type.clone(), + decoder, + }) + } +} + +impl ArrayDecoder for RunEndEncodedArrayDecoder { + fn decode(&mut self, tape: &Tape<'_>, pos: &[u32]) -> Result<ArrayData, ArrowError> { + let run_ends_type = match &self.data_type { + DataType::RunEndEncoded(r, _) => r.data_type(), + _ => unreachable!(), + }; + + let len = pos.len(); + if len == 0 { + let empty_run_ends = new_empty_run_ends(run_ends_type); + let empty_values = self.decoder.decode(tape, &[])?; + let data = ArrayDataBuilder::new(self.data_type.clone()) + .len(0) + .add_child_data(empty_run_ends) + .add_child_data(empty_values); + // Safety: + // Valid by construction + return Ok(unsafe { data.build_unchecked() }); + } + + let flat_data = self.decoder.decode(tape, pos)?; + + let mut run_ends: Vec<i64> = Vec::new(); + let mut mutable = MutableArrayData::new(vec![&flat_data], false, len); + + let mut run_start = 0; + for i in 1..len { + if !same_run(&flat_data, run_start, i) { + run_ends.push(i as i64); + mutable.extend(0, run_start, run_start + 1); + run_start = i; + } + } + run_ends.push(len as i64); + mutable.extend(0, run_start, run_start + 1); + + let values_data = mutable.freeze(); + let run_ends_data = build_run_ends_array(run_ends_type, run_ends)?; + + let data = ArrayDataBuilder::new(self.data_type.clone()) + .len(len) + .add_child_data(run_ends_data) + .add_child_data(values_data); + + // Safety: + // Valid by construction Review Comment: The `run_ends` are built strictly increasing from the encoding loop, with the last value always equal to `len`, and `values` has the same length as `run_ends`, so the REE layout invariants are satisfied. I can spell that out in the comment instead if you'd prefer. ########## arrow-json/src/reader/run_end_array.rs: ########## @@ -0,0 +1,150 @@ +// 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. + +use crate::reader::tape::Tape; +use crate::reader::{ArrayDecoder, DecoderContext}; +use arrow_array::Array; +use arrow_data::transform::MutableArrayData; +use arrow_data::{ArrayData, ArrayDataBuilder}; +use arrow_schema::{ArrowError, DataType}; + +pub struct RunEndEncodedArrayDecoder { + data_type: DataType, + decoder: Box<dyn ArrayDecoder>, +} + +impl RunEndEncodedArrayDecoder { + pub fn new( + ctx: &DecoderContext, + data_type: &DataType, + is_nullable: bool, + ) -> Result<Self, ArrowError> { + let values_field = match data_type { + DataType::RunEndEncoded(_, v) => v, + _ => unreachable!(), + }; + let decoder = ctx.make_decoder( + values_field.data_type(), + values_field.is_nullable() || is_nullable, + )?; + + Ok(Self { + data_type: data_type.clone(), + decoder, + }) + } +} + +impl ArrayDecoder for RunEndEncodedArrayDecoder { + fn decode(&mut self, tape: &Tape<'_>, pos: &[u32]) -> Result<ArrayData, ArrowError> { + let run_ends_type = match &self.data_type { + DataType::RunEndEncoded(r, _) => r.data_type(), + _ => unreachable!(), + }; + + let len = pos.len(); + if len == 0 { + let empty_run_ends = new_empty_run_ends(run_ends_type); + let empty_values = self.decoder.decode(tape, &[])?; + let data = ArrayDataBuilder::new(self.data_type.clone()) + .len(0) + .add_child_data(empty_run_ends) + .add_child_data(empty_values); + // Safety: + // Valid by construction + return Ok(unsafe { data.build_unchecked() }); + } + + let flat_data = self.decoder.decode(tape, pos)?; + + let mut run_ends: Vec<i64> = Vec::new(); + let mut mutable = MutableArrayData::new(vec![&flat_data], false, len); + + let mut run_start = 0; + for i in 1..len { + if !same_run(&flat_data, run_start, i) { + run_ends.push(i as i64); + mutable.extend(0, run_start, run_start + 1); + run_start = i; + } + } + run_ends.push(len as i64); + mutable.extend(0, run_start, run_start + 1); + + let values_data = mutable.freeze(); + let run_ends_data = build_run_ends_array(run_ends_type, run_ends)?; + + let data = ArrayDataBuilder::new(self.data_type.clone()) + .len(len) + .add_child_data(run_ends_data) + .add_child_data(values_data); + + // Safety: + // Valid by construction + Ok(unsafe { data.build_unchecked() }) + } +} + +fn same_run(data: &ArrayData, i: usize, j: usize) -> bool { + let null_i = data.is_null(i); + let null_j = data.is_null(j); + if null_i != null_j { + return false; + } + if null_i { + return true; + } + data.slice(i, 1) == data.slice(j, 1) +} + +fn build_run_ends_array(dt: &DataType, run_ends: Vec<i64>) -> Result<ArrayData, ArrowError> { Review Comment: good idea, I'll make the decoder generic over `R: RunEndIndexType` and dispatch in `make_decoder`, that removes the `i64` conversion entirely. -- This is an automated message from the Apache Git Service. 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