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⚡ [Optimize string cloning in DB query loops] #276

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⚡ [Optimize string cloning in DB query loops] #276

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8b13173
Optimize database row iteration to avoid string allocation overhead
google-labs-jules[bot] Oct 7, 2026
2aa8155
Optimize database row iteration to avoid string allocation overhead
google-labs-jules[bot] Oct 7, 2026
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17 changes: 12 additions & 5 deletions stdlib/src/database.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,12 @@ fn std_database_query(
})?;

let mut result_rows = Vec::new();
let mut prototype_map = IndexMap::with_capacity(column_names.len());
let mut col_to_map_idx = Vec::with_capacity(column_names.len());
for name in column_names.iter() {
let (map_idx, _) = prototype_map.insert_full(name.clone(), RuntimeValue::Null);
col_to_map_idx.push(map_idx);
}

while let Some(row) = rows.next().map_err(|e| {
RuntimeError::new(
Expand All @@ -144,8 +150,8 @@ fn std_database_query(
None,
)
})? {
let mut row_map = IndexMap::with_capacity(column_names.len());
for (idx, name) in column_names.iter().enumerate() {
let mut row_map = prototype_map.clone();
for idx in 0..column_names.len() {
let value = match row.get_ref(idx).map_err(|e| {
RuntimeError::new(
RuntimeErrorKind::InvalidOperation(format!("Database column get error: {}", e)),
Expand All @@ -165,9 +171,10 @@ fn std_database_query(
RuntimeValue::Str(s)
}
};
// The clone here is strictly necessary because `IndexMap` requires an owned `String`
// key, and each row constructs a fresh map containing these keys.
row_map.insert(name.clone(), value);
let map_idx = col_to_map_idx[idx];
if let Some((_, v)) = row_map.get_index_mut(map_idx) {
*v = value;
}
}
result_rows.push(RuntimeValue::Map {
entries: Rc::new(RefCell::new(row_map)),
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14 changes: 12 additions & 2 deletions stdlib/src/sqlite.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -181,9 +181,16 @@ impl StdlibRegistry {
.collect();

let mut rows = Vec::new();
let mut prototype_map = IndexMap::with_capacity(col_count);
let mut col_to_map_idx = Vec::with_capacity(col_count);
for name in col_names.iter() {
let (map_idx, _) = prototype_map.insert_full(name.clone(), RuntimeValue::Null);
col_to_map_idx.push(map_idx);
}

let row_iter = stmt
.query_map(rusqlite::params_from_iter(params), |row| {
let mut map = IndexMap::with_capacity(col_count);
let mut map = prototype_map.clone();
for i in 0..col_count {
let val = row.get_ref_unwrap(i);
let rt_val = match val {
Expand All @@ -207,7 +214,10 @@ impl StdlibRegistry {
)
}
};
map.insert(col_names[i].clone(), rt_val);
let map_idx = col_to_map_idx[i];
if let Some((_, v)) = map.get_index_mut(map_idx) {
*v = rt_val;
}
}
Ok(map)
})
Expand Down