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//
// Unified Query Algebra
//
// Copyright (c) 2023-2026 Cognica, Inc.
//
//! Command-mutation-overlay table scan merging.
use super::{EngineTableRowSource, SQLError, Value};
use std::sync::Arc;
enum CommandScanCandidate {
Persisted(uqa_core::DocId),
Overlay(uqa_core::DocId, uqa_storage::document_store::Document),
}
impl EngineTableRowSource {
pub(super) fn next_command_physical_rows_batch(
&mut self,
max_rows: usize,
) -> uqa_execution::ExecResult<Vec<uqa_execution::PhysicalRow>> {
let Some(overlay_changes) = self.command_changes.as_ref().map(Arc::clone) else {
return Err(SQLError::Internal("command scan has no mutation overlay".into()).into());
};
let has_virtual = crate::engine_generated::projection_contains_virtual_generated_column(
&self.column_definitions,
&self.columns,
);
let mut rows = Vec::with_capacity(max_rows);
while rows.len() < max_rows {
let remaining = max_rows - rows.len();
let mut candidates = Vec::with_capacity(remaining);
let mut exhausted = false;
while candidates.len() < remaining {
if self.command_base_ids.is_empty() && !self.command_base_exhausted {
let page_size = remaining.max(uqa_execution::DEFAULT_BATCH_SIZE);
let doc_ids = self
.table
.document_store
.read()
.next_doc_ids(self.command_base_after, page_size)
.map_err(|error| {
SQLError::Internal(format!(
"scan command-visible document ids from `{}`: {error}",
self.table_name
))
})?;
if let Some(last) = doc_ids.last().copied() {
self.command_base_after = Some(last);
self.command_base_ids.extend(doc_ids);
} else {
self.command_base_exhausted = true;
}
}
let next_base = self.command_base_ids.front().copied();
let change_start = self
.command_change_after
.map_or(std::ops::Bound::Unbounded, std::ops::Bound::Excluded);
let next_change = overlay_changes
.range((change_start, std::ops::Bound::Unbounded))
.next();
match (next_base, next_change) {
(Some(base), Some((overlay_id, _))) if base < *overlay_id => {
self.command_base_ids.pop_front();
candidates.push(CommandScanCandidate::Persisted(base));
}
(Some(base), Some((overlay_id, document))) if base == *overlay_id => {
self.command_base_ids.pop_front();
self.command_change_after = Some(*overlay_id);
if let Some(document) = document {
candidates
.push(CommandScanCandidate::Overlay(*overlay_id, document.clone()));
}
}
(Some(_), Some((overlay_id, document))) => {
self.command_change_after = Some(*overlay_id);
if let Some(document) = document {
candidates
.push(CommandScanCandidate::Overlay(*overlay_id, document.clone()));
}
}
(Some(base), None) => {
self.command_base_ids.pop_front();
candidates.push(CommandScanCandidate::Persisted(base));
}
(None, Some((overlay_id, document))) => {
self.command_change_after = Some(*overlay_id);
if let Some(document) = document {
candidates
.push(CommandScanCandidate::Overlay(*overlay_id, document.clone()));
}
}
(None, None) => {
exhausted = self.command_base_exhausted;
break;
}
}
}
if candidates.is_empty() {
if exhausted {
break;
}
continue;
}
let persisted_ids = candidates
.iter()
.filter_map(|candidate| match candidate {
CommandScanCandidate::Persisted(doc_id) => Some(*doc_id),
CommandScanCandidate::Overlay(_, _) => None,
})
.collect::<Vec<_>>();
let mut persisted_documents = std::collections::BTreeMap::new();
let mut persisted_values = std::collections::BTreeMap::new();
let mut persisted_shared = None;
if !persisted_ids.is_empty() {
let store = self.table.document_store.read();
if has_virtual {
persisted_documents = store.get_many(&persisted_ids).map_err(|error| {
SQLError::Internal(format!(
"read command-visible generated rows from `{}`: {error}",
self.table_name
))
})?;
} else {
let fields = self
.columns
.iter()
.map(|column| {
crate::sql::storage_projection_column_for_table(
column,
&self.column_definitions,
)
})
.collect::<Vec<_>>();
if let Some(shared_rows) = store
.get_shared_fields(&persisted_ids, &fields)
.map_err(|error| {
SQLError::Internal(format!(
"read shared command-visible projected rows from `{}`: {error}",
self.table_name
))
})?
{
if shared_rows.len() != persisted_ids.len() {
return Err(SQLError::Internal(format!(
"table `{}` returned {} shared command rows for {} document ids",
self.table_name,
shared_rows.len(),
persisted_ids.len()
))
.into());
}
persisted_shared = Some(
persisted_ids
.iter()
.copied()
.zip(shared_rows)
.collect::<std::collections::BTreeMap<_, _>>(),
);
} else {
persisted_values = store
.get_fields_multi(&persisted_ids, &fields)
.map_err(|error| {
SQLError::Internal(format!(
"read command-visible projected rows from `{}`: {error}",
self.table_name
))
})?;
}
}
}
for candidate in candidates {
let (doc_id, physical) = match candidate {
CommandScanCandidate::Persisted(doc_id) if has_virtual => {
let mut document = persisted_documents.remove(&doc_id).ok_or_else(|| {
SQLError::Internal(format!(
"table `{}` listed command-visible document {doc_id} but did not return it",
self.table_name
))
})?;
crate::engine_generated::materialize_projected_virtual_generated_columns(
&self.column_definitions,
&mut document,
&self.columns,
)?;
let values = self
.columns
.iter()
.map(|column| {
document
.get(crate::sql::storage_projection_column_for_table(
column,
&self.column_definitions,
))
.cloned()
.unwrap_or(Value::Null)
})
.collect();
(doc_id, uqa_execution::PhysicalRow::from_values(values))
}
CommandScanCandidate::Persisted(doc_id) => {
let physical = if let Some(shared_rows) = persisted_shared.as_mut() {
match shared_rows.remove(&doc_id).flatten() {
Some(shared) => {
let (values, projection) = shared.into_parts();
uqa_execution::PhysicalRow::from_shared_values(
values, projection,
)
}
None => uqa_execution::PhysicalRow::nulls(self.columns.len()),
}
} else {
uqa_execution::PhysicalRow::from_values(
persisted_values
.remove(&doc_id)
.unwrap_or_else(|| vec![Value::Null; self.columns.len()]),
)
};
(doc_id, physical)
}
CommandScanCandidate::Overlay(doc_id, mut document) => {
crate::engine_generated::materialize_projected_virtual_generated_columns(
&self.column_definitions,
&mut document,
&self.columns,
)?;
let values = self
.columns
.iter()
.map(|column| {
document
.get(crate::sql::storage_projection_column_for_table(
column,
&self.column_definitions,
))
.cloned()
.unwrap_or(Value::Null)
})
.collect();
(doc_id, uqa_execution::PhysicalRow::from_values(values))
}
};
if let Some(predicate) = self.predicate.as_ref() {
if !predicate.keep_row(&self.physical_schema.view(&physical))? {
continue;
}
}
rows.push(self.with_lock_identity(physical, doc_id)?);
}
if exhausted {
break;
}
}
Ok(rows)
}
}