From 66a55b55b9e8ad7bea824c5c7db2214dc75de330 Mon Sep 17 00:00:00 2001
From: Greg Heartsfield <scsibug@imap.cc>
Date: Fri, 6 Jan 2023 12:17:30 -0600
Subject: [PATCH] perf: new index, manually selected when appropriate

---
 src/db.rs     | 24 +++++++++++++++++++++++-
 src/schema.rs | 27 ++++++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/src/db.rs b/src/db.rs
index 291a4a7..6fbdbd5 100644
--- a/src/db.rs
+++ b/src/db.rs
@@ -501,6 +501,22 @@ fn repeat_vars(count: usize) -> String {
     s
 }
 
+/// Decide if there is an index that should be used explicitly
+fn override_index(f: &ReqFilter) -> Option<String> {
+    // queries for multiple kinds default to kind_index, which is
+    // significantly slower than kind_created_at_index.
+    if let Some(ks) = &f.kinds {
+	if f.ids.is_none() &&
+	    ks.len() > 1 &&
+	    f.since.is_none() &&
+	    f.until.is_none() &&
+	    f.authors.is_none() {
+		return Some("kind_created_at_index".into());
+	    }
+    }
+    None
+}
+
 /// Create a dynamic SQL subquery and params from a subscription filter.
 fn query_from_filter(f: &ReqFilter) -> (String, Vec<Box<dyn ToSql>>) {
     // build a dynamic SQL query.  all user-input is either an integer
@@ -516,7 +532,13 @@ fn query_from_filter(f: &ReqFilter) -> (String, Vec<Box<dyn ToSql>>) {
         return (empty_query, empty_params);
     }
 
-    let mut query = "SELECT e.content, e.created_at FROM event e".to_owned();
+    // check if the index needs to be overriden
+    let idx_name = override_index(&f);
+    if let Some(n) = &idx_name {
+	info!("using explicit index: {:?}", n);
+    }
+    let idx_stmt = idx_name.map_or_else(|| "".to_owned(), |i| format!("INDEXED BY {}",i));
+    let mut query = format!("SELECT e.content, e.created_at FROM event e {}", idx_stmt);
     // query parameters for SQLite
     let mut params: Vec<Box<dyn ToSql>> = vec![];
 
diff --git a/src/schema.rs b/src/schema.rs
index b5ab8ac..62c82e7 100644
--- a/src/schema.rs
+++ b/src/schema.rs
@@ -20,7 +20,7 @@ pragma mmap_size = 17179869184; -- cap mmap at 16GB
 "##;
 
 /// Latest database version
-pub const DB_VERSION: usize = 13;
+pub const DB_VERSION: usize = 14;
 
 /// Schema definition
 const INIT_SQL: &str = formatcp!(
@@ -50,10 +50,12 @@ content TEXT NOT NULL -- serialized json of event object
 -- Event Indexes
 CREATE UNIQUE INDEX IF NOT EXISTS event_hash_index ON event(event_hash);
 CREATE INDEX IF NOT EXISTS author_index ON event(author);
+CREATE INDEX IF NOT EXISTS kind_index ON event(kind);
 CREATE INDEX IF NOT EXISTS created_at_index ON event(created_at);
 CREATE INDEX IF NOT EXISTS delegated_by_index ON event(delegated_by);
 CREATE INDEX IF NOT EXISTS event_composite_index ON event(kind,created_at);
 CREATE INDEX IF NOT EXISTS kind_author_index ON event(kind,author);
+CREATE INDEX IF NOT EXISTS kind_created_at_index ON event(kind,created_at);
 
 -- Tag Table
 -- Tag values are stored as either a BLOB (if they come in as a
@@ -193,6 +195,9 @@ pub fn upgrade_db(conn: &mut PooledConnection) -> Result<()> {
             if curr_version == 12 {
                 curr_version = mig_12_to_13(conn)?;
             }
+            if curr_version == 13 {
+                curr_version = mig_13_to_14(conn)?;
+            }
 
             if curr_version == DB_VERSION {
                 info!(
@@ -593,3 +598,23 @@ PRAGMA user_version = 13;
     }
     Ok(13)
 }
+
+fn mig_13_to_14(conn: &mut PooledConnection) -> Result<usize> {
+    info!("database schema needs update from 13->14");
+    let upgrade_sql = r##"
+CREATE INDEX IF NOT EXISTS kind_index ON event(kind);
+CREATE INDEX IF NOT EXISTS kind_created_at_index ON event(kind,created_at);
+pragma optimize;
+PRAGMA user_version = 14;
+"##;
+    match conn.execute_batch(upgrade_sql) {
+        Ok(()) => {
+            info!("database schema upgraded v13 -> v14");
+        }
+        Err(err) => {
+            error!("update failed: {}", err);
+            panic!("database could not be upgraded");
+        }
+    }
+    Ok(14)
+}