lora_store/memory/

mem_report.rs

//! Heap-byte breakdown of an [`InMemoryGraph`](super::InMemoryGraph).
//!
//! This is a *debug-only* estimator: it walks the graph's owned
//! structures and sums an approximation of their retained heap bytes,
//! attributed to the component that owns each allocation (node slab,
//! relationship slab, adjacency, label/type indexes, each secondary
//! index registry, the index catalog, the constraint catalog).
//!
//! The numbers it returns are *approximate*. `BTreeMap` and `HashMap`
//! both carry node/bucket overhead that varies with allocator state,
//! load factor, and Rust version; we use fixed amortised constants
//! ([`BTREE_PER_ENTRY`], [`HASHMAP_PER_ENTRY`]) so that callers can
//! diff two reports without the per-run noise an allocator-walking
//! profiler would introduce. For property keys, we count the
//! `Arc<str>` header but *not* the shared byte buffer — keys go
//! through the process-wide `super::super::intern` table, so adding
//! their content per occurrence would dramatically over-count the
//! marginal cost a property bag actually adds to the graph.
//!
//! Used by `crates/lora-database/benches/memory.rs` and the
//! `mem_probe*` examples in `crates/lora-server/examples/` to
//! attribute observed RSS growth to a specific component without
//! resorting to `dhat` / `heaptrack` for every run.

use std::collections::BTreeMap;
use std::mem::size_of;

use crate::{LoraBinary, LoraPoint, LoraVector, PropertyValue};

use super::chunked_vec::ChunkedVec;
use super::entity_index_store::{IndexBundle, ScopedPropertyKey};
use super::fulltext_index::FulltextRegistry;
use super::hnsw::HnswBackend;
use super::id_set::IdSet;
use super::index_catalog::{IndexCatalog, StoredIndexEntity};
use super::point_index::PointRegistry;
use super::property_index::{
    PropertyIndex, PropertyIndexKey, PropertyIndexRegistry, PropertyIndexState,
    PropertyValueBuckets,
};
use super::sorted_property_index::SortedPropertyIndex;
use super::text_index::TrigramRegistry;
use super::vector_index::{FlatBackend, VectorBackend, VectorIndexRegistry};
use super::ConstraintCatalog;

/// Amortised heap overhead per `BTreeMap` entry. Empirically a BTree
/// inner node holds ~11 entries in a ~256-byte allocation, so the
/// per-entry share is roughly 24 bytes.
const BTREE_PER_ENTRY: usize = 24;

/// Amortised heap overhead per `HashMap` entry — bucket pointer plus
/// hash table load factor.
const HASHMAP_PER_ENTRY: usize = 24;

/// `std::sync::Arc<T>`: strong + weak refcount header that precedes
/// the inline `T` allocation.
const ARC_HEADER: usize = 16;
/// An `Arc<str>` key: the fat pointer plus the allocation's refcounts
/// (the bytes are charged separately).
const ARC_STR_BYTES: usize = 16 + ARC_HEADER;

/// Aggregated retained-heap breakdown of an [`InMemoryGraph`].
///
/// All fields are in *bytes*. `usize` was chosen over `u64` so call
/// sites can use `cargo bench` reports and pretty-print without casts;
/// on 32-bit hosts a graph that overflowed this would already have
/// failed earlier.
#[derive(Debug, Default, Clone, PartialEq, serde::Serialize, serde::Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct MemoryReport {
    pub live_node_count: usize,
    pub live_relationship_count: usize,
    pub node_tombstone_count: usize,
    pub relationship_tombstone_count: usize,

    /// `nodes`: the slot tree plus each live node's encoded record (an
    /// 8-byte header and its bytes), and the graph's name dictionaries.
    pub nodes_bytes: usize,
    /// `relationships`: the slot tree plus each encoded record.
    pub relationships_bytes: usize,

    /// `outgoing`: the slot tree plus the heap of every adjacency list
    /// too long to sit inline.
    pub outgoing_bytes: usize,
    /// Same for `incoming`.
    pub incoming_bytes: usize,

    /// `nodes_by_label: BTreeMap<String, ChunkedVec<NodeId>>`.
    pub label_index_bytes: usize,
    /// `relationships_by_type: BTreeMap<String, ChunkedVec<RelationshipId>>`.
    pub type_index_bytes: usize,

    /// Hash-bucket property registry (`find_*_by_property`).
    pub property_index_bytes: usize,
    /// Sorted-range property index (`RANGE` catalog entries).
    pub sorted_index_bytes: usize,
    /// Trigram TEXT indexes.
    pub text_index_bytes: usize,
    /// Spatial grid POINT indexes.
    pub point_index_bytes: usize,
    /// FULLTEXT inverted indexes.
    pub fulltext_index_bytes: usize,
    /// VECTOR indexes (Flat and HNSW backends).
    pub vector_index_bytes: usize,

    pub index_catalog_bytes: usize,
    pub constraint_catalog_bytes: usize,

    /// Planner distinct-value sketches: one per (label / type, property
    /// key) that any live entity carries (see `GraphStats`).
    #[serde(default)]
    pub distinct_stats_bytes: usize,
    /// Number of those sketches.
    #[serde(default)]
    pub distinct_stats_sketches: usize,

    /// Per-key breakdown of [`Self::property_index_bytes`]: one entry per
    /// active hash property index (node and relationship keys), with
    /// whether a declaration keeps it active. Implicit (`declared ==
    /// false`) entries were built by an equality lookup on an undeclared
    /// key; they are not listed by `SHOW INDEXES`, live until the process
    /// exits, and are not rebuilt on restart (the next lookup builds them
    /// again). Sorted by entity, then key.
    #[serde(default)]
    pub property_index_keys: Vec<PropertyIndexKeyUsage>,
}

/// One active hash property index key in a [`MemoryReport`].
#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct PropertyIndexKeyUsage {
    pub entity: StoredIndexEntity,
    pub key: String,
    /// `true` when a declared RANGE index or a uniqueness / key
    /// constraint (through its backing RANGE index) on this key exists.
    /// `false` for an implicit, lookup-activated index — including one
    /// whose RANGE index was dropped (dropping the declaration leaves the
    /// hash buckets in place for later lookups).
    pub declared: bool,
    /// Estimated bytes of the across-scopes buckets plus every per-label /
    /// per-type scope of this key. Same methodology as
    /// [`MemoryReport::property_index_bytes`].
    pub bytes: usize,
}

impl MemoryReport {
    /// Bytes attributable to the core graph shape: slabs, adjacency,
    /// and the label/type indexes. This is the floor every workload
    /// pays regardless of which secondary indexes are installed.
    pub fn graph_core_bytes(&self) -> usize {
        self.nodes_bytes
            + self.relationships_bytes
            + self.outgoing_bytes
            + self.incoming_bytes
            + self.label_index_bytes
            + self.type_index_bytes
    }

    /// Bytes attributable to secondary indexes — the amount that would
    /// be reclaimed by dropping every index.
    pub fn secondary_index_bytes(&self) -> usize {
        self.property_index_bytes
            + self.sorted_index_bytes
            + self.text_index_bytes
            + self.point_index_bytes
            + self.fulltext_index_bytes
            + self.vector_index_bytes
    }

    /// Active hash property index keys that no declaration covers.
    pub fn implicit_property_index_keys(&self) -> impl Iterator<Item = &PropertyIndexKeyUsage> {
        self.property_index_keys.iter().filter(|k| !k.declared)
    }

    /// Estimated bytes held by implicit (lookup-activated) hash property
    /// indexes: the part of [`Self::property_index_bytes`] nothing declared.
    pub fn implicit_property_index_bytes(&self) -> usize {
        self.implicit_property_index_keys().map(|k| k.bytes).sum()
    }

    pub fn catalog_bytes(&self) -> usize {
        self.index_catalog_bytes + self.constraint_catalog_bytes
    }

    pub fn total_bytes(&self) -> usize {
        self.graph_core_bytes()
            + self.secondary_index_bytes()
            + self.catalog_bytes()
            + self.distinct_stats_bytes
    }

    /// Average retained bytes per live node, including its share of
    /// the slab tombstone overhead. Returns 0 when there are no
    /// nodes.
    pub fn bytes_per_live_node(&self) -> f64 {
        ratio(self.nodes_bytes, self.live_node_count)
    }

    pub fn bytes_per_live_relationship(&self) -> f64 {
        ratio(self.relationships_bytes, self.live_relationship_count)
    }

    /// One-line breakdown for bench / probe output. Stable enough for
    /// `grep`-friendly snapshot diffs across runs.
    pub fn summary(&self) -> String {
        format!(
            "total={} graph={} (nodes={} rels={} out={} in={} labels={} types={}) idx={} \
             implicit_idx={} ({} keys) cat={} stats={}",
            self.total_bytes(),
            self.graph_core_bytes(),
            self.nodes_bytes,
            self.relationships_bytes,
            self.outgoing_bytes,
            self.incoming_bytes,
            self.label_index_bytes,
            self.type_index_bytes,
            self.secondary_index_bytes(),
            self.implicit_property_index_bytes(),
            self.implicit_property_index_keys().count(),
            self.catalog_bytes(),
            self.distinct_stats_bytes,
        )
    }
}

fn ratio(num: usize, denom: usize) -> f64 {
    if denom == 0 {
        0.0
    } else {
        num as f64 / denom as f64
    }
}

pub(super) fn estimate(graph: &super::InMemoryGraph) -> MemoryReport {
    let mut report = MemoryReport {
        live_node_count: graph.live_node_count,
        live_relationship_count: graph.live_rel_count,
        node_tombstone_count: graph.nodes.len().saturating_sub(graph.live_node_count),
        relationship_tombstone_count: graph
            .relationships
            .len()
            .saturating_sub(graph.live_rel_count),
        ..MemoryReport::default()
    };

    report.nodes_bytes = record_slab_bytes(&graph.nodes) + graph.dicts.heap_bytes();
    report.relationships_bytes = record_slab_bytes(&graph.relationships);
    report.outgoing_bytes = adjacency_bytes(&graph.outgoing);
    report.incoming_bytes = adjacency_bytes(&graph.incoming);
    report.label_index_bytes = label_or_type_bytes(&graph.nodes_by_label);
    report.type_index_bytes = label_or_type_bytes(&graph.relationships_by_type);
    let sketches = &graph.distinct_stats;
    report.distinct_stats_bytes = sketches.nodes.heap_bytes() + sketches.relationships.heap_bytes();
    report.distinct_stats_sketches =
        sketches.nodes.sketch_count() + sketches.relationships.sketch_count();

    let bundle = &graph.indexes;
    if let Ok(props) = bundle.properties.read() {
        report.property_index_bytes = property_registry_bytes(&props);
        let declared = graph.declared_property_index_keys();
        for (entity, state) in [
            (StoredIndexEntity::Node, &props.node_properties),
            (
                StoredIndexEntity::Relationship,
                &props.relationship_properties,
            ),
        ] {
            for key in state.active_keys.iter() {
                report.property_index_keys.push(PropertyIndexKeyUsage {
                    entity,
                    key: key.clone(),
                    declared: declared.contains(&(entity, key.clone())),
                    bytes: property_key_bytes(state, key),
                });
            }
        }
    }
    report.sorted_index_bytes = sorted_registry_bytes(bundle);
    report.text_index_bytes = text_registry_bytes(bundle);
    report.point_index_bytes = point_registry_bytes(bundle);
    report.fulltext_index_bytes = fulltext_registry_bytes(bundle);
    report.vector_index_bytes = vector_registry_bytes(bundle);

    if let Ok(catalog) = bundle.catalog.read() {
        report.index_catalog_bytes = index_catalog_bytes(&catalog);
    }
    if let Ok(catalog) = graph.constraint_catalog.read() {
        report.constraint_catalog_bytes = constraint_catalog_bytes(&catalog);
    }

    report
}

// ---------------- slab + adjacency ----------------

/// Slot storage of a [`ChunkedVec`]: every allocated slot plus one
/// `Arc<Vec<T>>` chunk header and pointer per chunk, plus the root and
/// interior nodes above the chunks.
fn chunked_outer_bytes<T>(v: &ChunkedVec<T>) -> usize {
    v.capacity() * size_of::<T>()
        + v.chunk_count() * (ARC_HEADER + size_of::<Vec<T>>() + size_of::<usize>())
        + v.tree_overhead_bytes()
}

/// A slab of encoded records: the chunk tree plus each record's
/// allocation (an 8-byte header and its bytes).
fn record_slab_bytes(slab: &ChunkedVec<Option<crate::encoded::Blob>>) -> usize {
    chunked_outer_bytes(slab)
        + slab
            .iter()
            .flatten()
            .map(|blob| blob.alloc_bytes())
            .sum::<usize>()
}

fn adjacency_bytes(adj: &ChunkedVec<super::adjacency::AdjList>) -> usize {
    // Short lists are inline and own no heap; spilled ones do.
    chunked_outer_bytes(adj) + adj.iter().map(|list| list.heap_bytes()).sum::<usize>()
}

fn label_or_type_bytes(map: &BTreeMap<String, ChunkedVec<u64>>) -> usize {
    let mut total = 0;
    for (key, ids) in map {
        total += BTREE_PER_ENTRY
            + size_of::<String>()
            + key.capacity()
            + size_of::<ChunkedVec<u64>>()
            + chunked_outer_bytes(ids);
    }
    total
}

// ---------------- property values ----------------

/// Bytes beyond the embedded discriminant of a [`PropertyValue`]. The
/// embedded discriminant itself is counted by the caller (it sits
/// inside whatever container owns the value).
pub fn property_value_heap_bytes(value: &PropertyValue) -> usize {
    match value {
        PropertyValue::Null
        | PropertyValue::Bool(_)
        | PropertyValue::Int(_)
        | PropertyValue::Float(_)
        | PropertyValue::Date(_)
        | PropertyValue::Time(_)
        | PropertyValue::LocalTime(_)
        | PropertyValue::LocalDateTime(_)
        | PropertyValue::DateTime(_)
        | PropertyValue::Duration(_) => 0,
        PropertyValue::String(s) => s.capacity(),
        PropertyValue::Binary(b) => binary_heap_bytes(b),
        PropertyValue::Point(p) => point_heap_bytes(p),
        PropertyValue::Vector(v) => vector_heap_bytes(v),
        PropertyValue::List(items) => {
            items.capacity() * size_of::<PropertyValue>()
                + items.iter().map(property_value_heap_bytes).sum::<usize>()
        }
        PropertyValue::Map(map) => {
            let mut total = 0;
            for (key, value) in map {
                total += BTREE_PER_ENTRY
                    + size_of::<String>()
                    + key.capacity()
                    + size_of::<PropertyValue>()
                    + property_value_heap_bytes(value);
            }
            total
        }
    }
}

fn binary_heap_bytes(b: &LoraBinary) -> usize {
    let mut total = std::mem::size_of_val(b.segments());
    for seg in b.segments() {
        total += seg.capacity();
    }
    total
}

fn point_heap_bytes(_: &LoraPoint) -> usize {
    // LoraPoint is fixed-size (3 × f64 + tag + srid). No owned heap.
    0
}

fn vector_heap_bytes(v: &LoraVector) -> usize {
    use crate::types::VectorValues;
    match &v.values {
        VectorValues::Float64(xs) => xs.capacity() * size_of::<f64>(),
        VectorValues::Float32(xs) => xs.capacity() * size_of::<f32>(),
        VectorValues::Integer64(xs) => xs.capacity() * size_of::<i64>(),
        VectorValues::Integer32(xs) => xs.capacity() * size_of::<i32>(),
        VectorValues::Integer16(xs) => xs.capacity() * size_of::<i16>(),
        VectorValues::Integer8(xs) => xs.capacity() * size_of::<i8>(),
    }
}

// ---------------- secondary indexes ----------------

fn property_registry_bytes(reg: &PropertyIndexRegistry) -> usize {
    property_state_bytes(&reg.node_properties) + property_state_bytes(&reg.relationship_properties)
}

fn property_state_bytes(state: &PropertyIndexState) -> usize {
    let mut total = 0;
    for key in state.active_keys.iter() {
        total += BTREE_PER_ENTRY + size_of::<String>() + key.capacity();
    }
    total += property_index_map_bytes(&state.any_scope);
    for (scope, by_property) in state.scoped_values.iter() {
        total += HASHMAP_PER_ENTRY + ARC_STR_BYTES + scope.len();
        total += ARC_HEADER + property_index_map_bytes(by_property);
    }
    total
}

fn property_index_map_bytes(values: &PropertyIndex) -> usize {
    values
        .iter()
        .map(|(key, buckets)| property_buckets_bytes(key, buckets))
        .sum()
}

fn property_buckets_bytes(key: &str, buckets: &PropertyValueBuckets) -> usize {
    let mut total = HASHMAP_PER_ENTRY + ARC_STR_BYTES + key.len() + buckets.structure_bytes();
    for (indexed, ids) in buckets.iter() {
        total += HASHMAP_PER_ENTRY
            + property_index_key_bytes(indexed)
            + size_of::<IdSet>()
            + ids.heap_bytes();
    }
    total
}

/// Bytes one active key holds in a [`PropertyIndexState`]: its
/// active-key entry and its buckets in every scope.
/// Per-scope map headers are shared by every key and not attributed.
fn property_key_bytes(state: &PropertyIndexState, key: &String) -> usize {
    let mut total = BTREE_PER_ENTRY + size_of::<String>() + key.capacity();
    if let Some(buckets) = state.any_scope.get(key.as_str()) {
        total += property_buckets_bytes(key, buckets);
    }
    for by_property in state.scoped_values.values() {
        if let Some(buckets) = by_property.get(key.as_str()) {
            total += property_buckets_bytes(key, buckets);
        }
    }
    total
}

fn property_index_key_bytes(key: &PropertyIndexKey) -> usize {
    size_of::<PropertyIndexKey>()
        + match key {
            PropertyIndexKey::Null
            | PropertyIndexKey::Bool(_)
            | PropertyIndexKey::Int(_)
            | PropertyIndexKey::Float(_)
            | PropertyIndexKey::Temporal { .. } => 0,
            PropertyIndexKey::String(s) => 16 + s.len(),
            PropertyIndexKey::Binary(b) => binary_heap_bytes(b),
            PropertyIndexKey::List(items) => {
                items.capacity() * size_of::<PropertyIndexKey>()
                    + items.iter().map(property_index_key_bytes).sum::<usize>()
            }
            PropertyIndexKey::Map(map) => map
                .iter()
                .map(|(k, v)| {
                    BTREE_PER_ENTRY
                        + size_of::<String>()
                        + k.capacity()
                        + property_index_key_bytes(v)
                })
                .sum::<usize>(),
        }
}

fn scoped_key_bytes(scope: &ScopedPropertyKey) -> usize {
    size_of::<ScopedPropertyKey>() + scope.label.capacity() + scope.property.capacity()
}

fn sorted_registry_bytes(bundle: &IndexBundle) -> usize {
    let node = bundle.sorted.read(StoredIndexEntity::Node);
    let rel = bundle.sorted.read(StoredIndexEntity::Relationship);
    sorted_one(&node) + sorted_one(&rel)
}

fn sorted_one(index: &SortedPropertyIndex) -> usize {
    let mut total = 0;
    for (scope, sorted_scope) in &index.by_scope {
        total +=
            BTREE_PER_ENTRY + scoped_key_bytes(scope) + sorted_scope.by_value.structure_bytes();
        // Entries sit in sorted arrays: charge every allocated slot, used
        // or not. `property_index_key_bytes` covers a used slot's key.
        let slots = sorted_scope.by_value.entry_slots();
        let unused = slots.saturating_sub(sorted_scope.by_value.len());
        total += slots * size_of::<IdSet>() + unused * size_of::<PropertyIndexKey>();
        for (indexed, ids) in sorted_scope.by_value.iter() {
            total += property_index_key_bytes(indexed) + ids.heap_bytes();
        }
    }
    total
}

fn text_registry_bytes(bundle: &IndexBundle) -> usize {
    let node = bundle.text.read(StoredIndexEntity::Node);
    let rel = bundle.text.read(StoredIndexEntity::Relationship);
    text_one(&node) + text_one(&rel)
}

fn text_one(registry: &TrigramRegistry) -> usize {
    let mut total = 0;
    for (scope, trigram_scope) in &registry.by_scope {
        total +=
            HASHMAP_PER_ENTRY + scoped_key_bytes(scope) + trigram_scope.grams.structure_bytes();
        for ids in trigram_scope.grams.values() {
            total += BTREE_PER_ENTRY + 3 + ids.heap_bytes();
        }
    }
    total
}

fn point_registry_bytes(bundle: &IndexBundle) -> usize {
    let node = bundle.point.read(StoredIndexEntity::Node);
    let rel = bundle.point.read(StoredIndexEntity::Relationship);
    point_one(&node) + point_one(&rel)
}

fn point_one(registry: &PointRegistry) -> usize {
    let mut total = 0;
    for (scope, scope_data) in &registry.by_scope {
        total +=
            HASHMAP_PER_ENTRY + scoped_key_bytes(scope) + scope_data.grid.cells.structure_bytes();
        for cell in scope_data.grid.cells.values() {
            total += HASHMAP_PER_ENTRY + cell.heap_bytes();
        }
    }
    total
}

fn fulltext_registry_bytes(bundle: &IndexBundle) -> usize {
    let node = bundle.fulltext.read(StoredIndexEntity::Node);
    let rel = bundle.fulltext.read(StoredIndexEntity::Relationship);
    fulltext_one(&node) + fulltext_one(&rel)
}

fn fulltext_one(registry: &FulltextRegistry) -> usize {
    let mut total = 0;
    for (name, index) in registry.iter() {
        total += HASHMAP_PER_ENTRY + size_of::<String>() + name.capacity();
        total += index.labels.capacity() * size_of::<String>();
        for label in &index.labels {
            total += label.capacity();
        }
        total += index.properties.capacity() * size_of::<String>();
        for property in &index.properties {
            total += property.capacity();
        }
        // Term strings are shared `Arc<str>`s: charged once, on the
        // postings key; the per-entity lists hold pointers.
        total += index.postings.structure_bytes() + index.entity_terms.structure_bytes();
        for (term, postings) in index.postings.iter() {
            total += BTREE_PER_ENTRY + size_of::<std::sync::Arc<str>>() + ARC_HEADER + term.len();
            total += postings.heap_bytes();
        }
        for terms in index.entity_terms.values() {
            total += BTREE_PER_ENTRY
                + size_of::<u64>()
                + ARC_HEADER
                + terms.len() * size_of::<std::sync::Arc<str>>();
        }
    }
    total
}

fn vector_registry_bytes(bundle: &IndexBundle) -> usize {
    let node = bundle.vector.read(StoredIndexEntity::Node);
    let rel = bundle.vector.read(StoredIndexEntity::Relationship);
    vector_one(&node) + vector_one(&rel)
}

fn vector_one(registry: &VectorIndexRegistry) -> usize {
    let mut total = 0;
    for (name, entry) in &registry.by_name {
        total += BTREE_PER_ENTRY
            + size_of::<String>()
            + name.capacity()
            + entry.label.capacity()
            + entry.property.capacity();
        total += match &entry.backend {
            VectorBackend::Flat(b) => flat_backend_bytes(b),
            VectorBackend::Hnsw(b) => hnsw_backend_bytes(b),
        };
    }
    total
}

fn flat_backend_bytes(b: &FlatBackend) -> usize {
    let mut total = 0;
    for v in b.items.values() {
        total +=
            BTREE_PER_ENTRY + size_of::<u64>() + size_of::<LoraVector>() + vector_heap_bytes(v);
    }
    total
}

fn hnsw_backend_bytes(b: &HnswBackend) -> usize {
    let mut total = 0;
    for node in b.nodes.values() {
        total += BTREE_PER_ENTRY
            + size_of::<u64>()
            + size_of::<LoraVector>()
            + vector_heap_bytes(&node.vector)
            + size_of::<usize>() // level
            + node.neighbors.capacity() * size_of::<Vec<u64>>();
        for layer in &node.neighbors {
            total += layer.capacity() * size_of::<u64>();
        }
    }
    total
}

// ---------------- catalogs ----------------

fn index_catalog_bytes(catalog: &IndexCatalog) -> usize {
    let mut total = 0;
    for def in catalog.list() {
        total += BTREE_PER_ENTRY + size_of::<String>() + def.name.capacity();
        if let Some(label) = &def.label {
            total += label.capacity();
        }
        for label in &def.additional_labels {
            total += size_of::<String>() + label.capacity();
        }
        for property in &def.properties {
            total += size_of::<String>() + property.capacity();
        }
        for key in def.options.keys() {
            total += BTREE_PER_ENTRY + size_of::<String>() + key.capacity();
        }
    }
    total
}

fn constraint_catalog_bytes(catalog: &ConstraintCatalog) -> usize {
    let mut total = 0;
    for def in catalog.list() {
        total += BTREE_PER_ENTRY + size_of::<String>() + def.name.capacity() + def.label.capacity();
        for property in &def.properties {
            total += size_of::<String>() + property.capacity();
        }
        if let Some(idx) = &def.owned_index {
            total += idx.capacity();
        }
    }
    total
}