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feat: expose stats schema on Snapshot #2128

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merged 1 commit into from
Jan 27, 2024
Merged

feat: expose stats schema on Snapshot #2128

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101 changes: 80 additions & 21 deletions crates/deltalake-core/src/kernel/snapshot/mod.rs
View file
Open in desktop
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
Open in desktop
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
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