Skip to content

Commit

Permalink
feat: expose stats schema on Snapshot (#2128)
Browse files Browse the repository at this point in the history 
# Description

The new table config `delta.dataSkippingStatsColumns` changes the logic
which columns should be considered when computing file statistics. Here
we expose (and use) a new method on `Snapshot` which reflects the
updated logic.

This PR does not contain any tests for the new code paths, but I'll test
this against the reference implementation once the new checkpoint writer
lands.
  • Loading branch information
@roeap
roeap authored Jan 27, 2024
1 parent 9199301 commit 64b2547
Show file tree
Hide file tree
Showing 2 changed files with 92 additions and 80 deletions.
101 changes: 80 additions & 21 deletions crates/deltalake-core/src/kernel/snapshot/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ use object_store::ObjectStore;
use self::log_segment::{CommitData, LogSegment, PathExt};
use self::parse::{read_adds, read_removes};
use self::replay::{LogMapper, LogReplayScanner, ReplayStream};
use super::{Action, Add, CommitInfo, Metadata, Protocol, Remove};
use super::{Action, Add, CommitInfo, DataType, Metadata, Protocol, Remove, StructField};
use crate::kernel::StructType;
use crate::table::config::TableConfig;
use crate::{DeltaResult, DeltaTableConfig, DeltaTableError};
Expand Down Expand Up @@ -69,8 +69,7 @@ impl Snapshot {
"Cannot read metadata from log segment".into(),
));
};
let metadata = metadata.unwrap();
let protocol = protocol.unwrap();
let (metadata, protocol) = (metadata.unwrap(), protocol.unwrap());
let schema = serde_json::from_str(&metadata.schema_string)?;
Ok(Self {
log_segment,
Expand Down Expand Up @@ -212,12 +211,7 @@ impl Snapshot {
&log_segment::CHECKPOINT_SCHEMA,
&self.config,
);
ReplayStream::try_new(
log_stream,
checkpoint_stream,
&self.schema,
self.config.clone(),
)
ReplayStream::try_new(log_stream, checkpoint_stream, &self)
}

/// Get the commit infos in the snapshot
Expand Down Expand Up @@ -288,6 +282,59 @@ impl Snapshot {
})
.boxed())
}

/// Get the statistics schema of the snapshot
pub fn stats_schema(&self) -> DeltaResult<StructType> {
let stats_fields = if let Some(stats_cols) = self.table_config().stats_columns() {
stats_cols
.iter()
.map(|col| match self.schema().field_with_name(col) {
Ok(field) => match field.data_type() {
DataType::Map(_) | DataType::Array(_) | &DataType::BINARY => {
Err(DeltaTableError::Generic(format!(
"Stats column {} has unsupported type {}",
col,
field.data_type()
)))
}
_ => Ok(StructField::new(
field.name(),
field.data_type().clone(),
true,
)),
},
_ => Err(DeltaTableError::Generic(format!(
"Stats column {} not found in schema",
col
))),
})
.collect::<Result<Vec<_>, _>>()?
} else {
let num_indexed_cols = self.table_config().num_indexed_cols();
self.schema()
.fields
.iter()
.enumerate()
.filter_map(|(idx, f)| match f.data_type() {
DataType::Map(_) | DataType::Array(_) | &DataType::BINARY => None,
_ if num_indexed_cols < 0 || (idx as i32) < num_indexed_cols => {
Some(StructField::new(f.name(), f.data_type().clone(), true))
}
_ => None,
})
.collect()
};
Ok(StructType::new(vec![
StructField::new("numRecords", DataType::LONG, true),
StructField::new("minValues", StructType::new(stats_fields.clone()), true),
StructField::new("maxValues", StructType::new(stats_fields.clone()), true),
StructField::new(
"nullCount",
StructType::new(stats_fields.iter().filter_map(to_count_field).collect()),
true,
),
]))
}
}

/// A snapshot of a Delta table that has been eagerly loaded into memory.
Expand Down Expand Up @@ -318,7 +365,7 @@ impl EagerSnapshot {
let mut files = Vec::new();
let mut scanner = LogReplayScanner::new();
files.push(scanner.process_files_batch(&batch, true)?);
let mapper = LogMapper::try_new(snapshot.schema(), snapshot.config.clone())?;
let mapper = LogMapper::try_new(&snapshot)?;
files = files
.into_iter()
.map(|b| mapper.map_batch(b))
Expand Down Expand Up @@ -357,16 +404,11 @@ impl EagerSnapshot {
)
.boxed()
};
let mapper = LogMapper::try_new(self.snapshot.schema(), self.snapshot.config.clone())?;
let files = ReplayStream::try_new(
log_stream,
checkpoint_stream,
self.schema(),
self.snapshot.config.clone(),
)?
.map(|batch| batch.and_then(|b| mapper.map_batch(b)))
.try_collect()
.await?;
let mapper = LogMapper::try_new(&self.snapshot)?;
let files = ReplayStream::try_new(log_stream, checkpoint_stream, &self.snapshot)?
.map(|batch| batch.and_then(|b| mapper.map_batch(b)))
.try_collect()
.await?;

self.files = files;
}
Expand Down Expand Up @@ -473,7 +515,7 @@ impl EagerSnapshot {
files.push(scanner.process_files_batch(&batch?, true)?);
}

let mapper = LogMapper::try_new(self.snapshot.schema(), self.snapshot.config.clone())?;
let mapper = LogMapper::try_new(&self.snapshot)?;
self.files = files
.into_iter()
.chain(
Expand All @@ -496,6 +538,23 @@ impl EagerSnapshot {
}
}

fn to_count_field(field: &StructField) -> Option<StructField> {
match field.data_type() {
DataType::Map(_) | DataType::Array(_) | &DataType::BINARY => None,
DataType::Struct(s) => Some(StructField::new(
field.name(),
StructType::new(
s.fields()
.iter()
.filter_map(to_count_field)
.collect::<Vec<_>>(),
),
true,
)),
_ => Some(StructField::new(field.name(), DataType::LONG, true)),
}
}

#[cfg(feature = "datafusion")]
mod datafusion {
use datafusion_common::stats::Statistics;
Expand Down
71 changes: 12 additions & 59 deletions crates/deltalake-core/src/kernel/snapshot/replay.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -21,9 +21,10 @@ use tracing::debug;

use crate::kernel::arrow::extract::{self as ex, ProvidesColumnByName};
use crate::kernel::arrow::json;
use crate::kernel::{DataType, Schema, StructField, StructType};
use crate::{DeltaResult, DeltaTableConfig, DeltaTableError};

use super::Snapshot;

pin_project! {
pub struct ReplayStream<S> {
scanner: LogReplayScanner,
Expand All @@ -38,60 +39,12 @@ pin_project! {
}
}

fn to_count_field(field: &StructField) -> Option<StructField> {
match field.data_type() {
DataType::Map(_) | DataType::Array(_) | &DataType::BINARY => None,
DataType::Struct(s) => Some(StructField::new(
field.name(),
StructType::new(
s.fields()
.iter()
.filter_map(to_count_field)
.collect::<Vec<_>>(),
),
true,
)),
_ => Some(StructField::new(field.name(), DataType::LONG, true)),
}
}

pub(super) fn get_stats_schema(table_schema: &StructType) -> DeltaResult<ArrowSchemaRef> {
let data_fields: Vec<_> = table_schema
.fields
.iter()
.enumerate()
.filter_map(|(idx, f)| match f.data_type() {
DataType::Map(_) | DataType::Array(_) | &DataType::BINARY => None,
// TODO: the number of stats fields shopuld be configurable?
// or rather we should likely read all of we parse JSON?
_ if idx < 32 => Some(StructField::new(f.name(), f.data_type().clone(), true)),
_ => None,
})
.collect();
let stats_schema = StructType::new(vec![
StructField::new("numRecords", DataType::LONG, true),
StructField::new("minValues", StructType::new(data_fields.clone()), true),
StructField::new("maxValues", StructType::new(data_fields.clone()), true),
StructField::new(
"nullCount",
StructType::new(data_fields.iter().filter_map(to_count_field).collect()),
true,
),
]);
Ok(std::sync::Arc::new((&stats_schema).try_into()?))
}

impl<S> ReplayStream<S> {
pub(super) fn try_new(
commits: S,
checkpoint: S,
table_schema: &Schema,
config: DeltaTableConfig,
) -> DeltaResult<Self> {
let stats_schema = get_stats_schema(table_schema)?;
pub(super) fn try_new(commits: S, checkpoint: S, snapshot: &Snapshot) -> DeltaResult<Self> {
let stats_schema = Arc::new((&snapshot.stats_schema()?).try_into()?);
let mapper = Arc::new(LogMapper {
stats_schema,
config,
config: snapshot.config.clone(),
});
Ok(Self {
commits,
Expand All @@ -108,10 +61,10 @@ pub(super) struct LogMapper {
}

impl LogMapper {
pub(super) fn try_new(table_schema: &Schema, config: DeltaTableConfig) -> DeltaResult<Self> {
pub(super) fn try_new(snapshot: &Snapshot) -> DeltaResult<Self> {
Ok(Self {
stats_schema: get_stats_schema(table_schema)?,
config,
stats_schema: Arc::new((&snapshot.stats_schema()?).try_into()?),
config: snapshot.config.clone(),
})
}

Expand All @@ -120,7 +73,7 @@ impl LogMapper {
}
}

pub(super) fn map_batch(
fn map_batch(
batch: RecordBatch,
stats_schema: ArrowSchemaRef,
config: &DeltaTableConfig,
Expand All @@ -135,7 +88,7 @@ pub(super) fn map_batch(
Arc::new(json::parse_json(stats, stats_schema.clone(), config)?.into());
let schema = batch.schema();
let add_col = ex::extract_and_cast::<StructArray>(&batch, "add")?;
let add_idx = schema.column_with_name("add").unwrap();
let (add_idx, _) = schema.column_with_name("add").unwrap();
let add_type = add_col
.fields()
.iter()
Expand All @@ -162,9 +115,9 @@ pub(super) fn map_batch(
true,
));
let mut fields = schema.fields().to_vec();
let _ = std::mem::replace(&mut fields[add_idx.0], new_add_field);
let _ = std::mem::replace(&mut fields[add_idx], new_add_field);
let mut columns = batch.columns().to_vec();
let _ = std::mem::replace(&mut columns[add_idx.0], new_add);
let _ = std::mem::replace(&mut columns[add_idx], new_add);
return Ok(RecordBatch::try_new(
Arc::new(ArrowSchema::new(fields)),
columns,
Expand Down

0 comments on commit 64b2547

Please sign in to comment.