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use crate::TViewResult;
use pgrx::prelude::*;
use std::collections::{HashMap, HashSet, VecDeque};
/// Entity dependency graph for refresh ordering
///
/// Example:
/// - `tv_company` (no dependencies)
/// - `tv_user` (depends on `tv_company` via `fk_company`)
/// - `tv_post` (depends on `tv_user` via `fk_user`)
/// - `tv_feed` (depends on `tv_post` via `fk_post`)
///
/// Topological order: `["company", "user", "post", "feed"]`
#[derive(Debug, Clone)]
pub struct EntityDepGraph {
/// Parent relationships: entity -> list of entities that depend on it
/// Example: "user" -> `["post", "feed"]`
#[allow(dead_code)] // Reason: public API for graph introspection; populated during load()
pub parents: HashMap<String, Vec<String>>,
/// Child relationships: entity -> list of entities it depends on
/// Example: "post" -> `["user"]`
#[allow(dead_code)] // Reason: public API for graph introspection; populated during load()
pub children: HashMap<String, Vec<String>>,
/// Topological order (refresh from low to high dependency)
/// Example: `["company", "user", "post", "feed"]`
pub topo_order: Vec<String>,
}
impl EntityDepGraph {
/// Build dependency graph from `pg_tview_meta`
pub fn load() -> TViewResult<Self> {
// Query pg_tview_meta for all entities and their FK columns
let query = "SELECT entity, fk_columns FROM pg_tview_meta";
let mut parents: HashMap<String, Vec<String>> = HashMap::new();
let mut children: HashMap<String, Vec<String>> = HashMap::new();
let mut all_entities: HashSet<String> = HashSet::new();
Spi::connect(|client| {
let rows = client.select(query, None, &[])?;
for row in rows {
let entity: String = row["entity"]
.value()
.map_err(|e| crate::TViewError::SpiError {
query: query.to_string(),
error: format!("Failed to get entity: {e}"),
})?
.ok_or_else(|| crate::TViewError::SpiError {
query: query.to_string(),
error: "entity column is NULL".to_string(),
})?;
let fk_columns: Option<Vec<String>> =
row["fk_columns"]
.value()
.map_err(|e| crate::TViewError::SpiError {
query: query.to_string(),
error: format!("Failed to get fk_columns: {e}"),
})?;
all_entities.insert(entity.clone());
if let Some(fk_cols) = fk_columns {
for fk_col in fk_cols {
// FK column format: "fk_<entity>"
// Example: "fk_user" -> "user"
if let Some(parent_entity) = fk_col.strip_prefix("fk_") {
// Register parent relationship
parents
.entry(parent_entity.to_string())
.or_default()
.push(entity.clone());
// Register child relationship
children
.entry(entity.clone())
.or_default()
.push(parent_entity.to_string());
}
}
}
}
Ok::<_, spi::SpiError>(())
})?;
// Compute topological order
let topo_order = topological_sort(&all_entities, &children)?;
Ok(Self {
parents,
children,
topo_order,
})
}
/// Sort refresh keys by dependency order
///
/// Keys are grouped by entity, then sorted by `topo_order`.
/// Within each entity group, insertion order is preserved.
/// Both PK and dedup keys are retained as-is.
pub fn sort_keys(&self, keys: Vec<super::key::RefreshKey>) -> Vec<super::key::RefreshKey> {
// Group by entity, preserving full RefreshKey values
let mut groups: HashMap<String, Vec<super::key::RefreshKey>> = HashMap::new();
for key in keys {
groups.entry(key.entity.clone()).or_default().push(key);
}
// Emit groups in topological order
let mut sorted_keys = Vec::new();
for entity in &self.topo_order {
if let Some(ks) = groups.remove(entity) {
sorted_keys.extend(ks);
}
}
sorted_keys
}
}
/// Topological sort using Kahn's algorithm
fn topological_sort(
entities: &HashSet<String>,
children: &HashMap<String, Vec<String>>,
) -> TViewResult<Vec<String>> {
// Calculate in-degree for each entity
let mut in_degree: HashMap<String, usize> = HashMap::new();
for entity in entities {
in_degree.insert(entity.clone(), 0);
}
for deps in children.values() {
for dep in deps {
*in_degree.entry(dep.clone()).or_insert(0) += 1;
}
}
// Start with entities that have no dependencies
let mut queue: VecDeque<String> = VecDeque::new();
for (entity, °ree) in &in_degree {
if degree == 0 {
queue.push_back(entity.clone());
}
}
let mut result = Vec::new();
while let Some(entity) = queue.pop_front() {
result.push(entity.clone());
// Find entities that depend on this one
if let Some(parents) = children.get(&entity) {
for parent in parents {
if let Some(degree) = in_degree.get_mut(parent) {
*degree -= 1;
if *degree == 0 {
queue.push_back(parent.clone());
}
}
}
}
}
// Check for cycles (only count entities in the original set;
// FK references to non-TVIEW entities like "user" are external and shouldn't
// cause cycle detection failures)
let result_in_set = result.iter().filter(|e| entities.contains(*e)).count();
if result_in_set != entities.len() {
return Err(crate::TViewError::DependencyCycle {
entities: entities.iter().cloned().collect(),
});
}
Ok(result)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_sort_keys_preserves_dedup_keys() {
// Build a simple graph: company -> user -> post
let graph = EntityDepGraph {
parents: HashMap::new(),
children: HashMap::new(),
topo_order: vec!["company".into(), "user".into(), "post".into()],
};
let keys = vec![
super::super::key::RefreshKey::pk("post", 10),
super::super::key::RefreshKey::dedup("user", "some-uuid"),
super::super::key::RefreshKey::pk("company", 1),
super::super::key::RefreshKey::pk("user", 42),
super::super::key::RefreshKey::dedup("post", "dedup-val"),
];
let sorted = graph.sort_keys(keys);
// All 5 keys must be present
assert_eq!(sorted.len(), 5);
// Dedup keys must survive with their dedup_key field intact
let dedup_keys: Vec<_> = sorted.iter().filter(|k| k.is_dedup()).collect();
assert_eq!(dedup_keys.len(), 2);
// Verify specific dedup keys are present with correct fields
assert!(sorted.contains(&super::super::key::RefreshKey::dedup("user", "some-uuid")));
assert!(sorted.contains(&super::super::key::RefreshKey::dedup("post", "dedup-val")));
// Verify topological order: company entities before user, user before post
let first_company = sorted.iter().position(|k| k.entity == "company").unwrap();
let first_user = sorted.iter().position(|k| k.entity == "user").unwrap();
let first_post = sorted.iter().position(|k| k.entity == "post").unwrap();
assert!(first_company < first_user);
assert!(first_user < first_post);
}
#[test]
fn test_topological_sort() {
// Entity graph:
// company (no deps)
// user -> company
// post -> user
// feed -> post
let entities: HashSet<String> = ["company", "user", "post", "feed"]
.iter()
.map(|&s| s.to_string())
.collect();
let mut children: HashMap<String, Vec<String>> = HashMap::new();
children.insert("user".to_string(), vec!["company".to_string()]);
children.insert("post".to_string(), vec!["user".to_string()]);
children.insert("feed".to_string(), vec!["post".to_string()]);
let topo = topological_sort(&entities, &children).unwrap();
// Valid topological orders:
// ["company", "user", "post", "feed"]
// Check that company comes before user, user before post, etc.
let company_idx = topo.iter().position(|e| e == "company").unwrap();
let user_idx = topo.iter().position(|e| e == "user").unwrap();
let post_idx = topo.iter().position(|e| e == "post").unwrap();
let feed_idx = topo.iter().position(|e| e == "feed").unwrap();
assert!(company_idx < user_idx);
assert!(user_idx < post_idx);
assert!(post_idx < feed_idx);
}
}