sqlite: add fts optimize command

This command will free up FTS space. Normally not needed, but if
trying to shrink the size of your database file it can be useful.

More or less equivalent to:

  INSERT INTO ft(ft) VALUES('optimize');

but uses the merge command to divide the task into multiple steps.

src/commands/sqlite/fts.rs

@@ -9,13 +9,14 @@ use crate::sqlite::{
 use anyhow::Result;
 use rusqlite::{params, Transaction};
 use serde_json::Value;
-use tracing::{info, warn};
+use tracing::{debug, info, warn};
 
 pub(super) fn fts(args: &FtsArgs) -> Result<()> {
     match &args.command {
         FtsCommand::Enable { force, filename } => fts_enable(force, filename),
         FtsCommand::Disable { force, filename } => fts_disable(force, filename),
         FtsCommand::Check { filename } => fts_check(filename),
+        FtsCommand::Optimize { filename } => fts_optimize(filename),
     }
 }
 
@@ -83,6 +84,41 @@ fn fts_check(filename: &str) -> Result<()> {
     Ok(())
 }
 
+fn fts_optimize(filename: &str) -> Result<()> {
+    let conn = ConnectionBuilder::filename(Some(filename)).open(false)?;
+
+    if !conn.has_table("fts")? {
+        warn!("FTS is not enabled");
+        return Ok(());
+    }
+
+    let get_total_changes = || -> Result<i64> {
+        let rows = conn.query_row("select total_changes()", [], |row| {
+            let count: i64 = row.get(0)?;
+            Ok(count)
+        })?;
+        Ok(rows)
+    };
+
+    let mut last_total_changes = get_total_changes()?;
+
+    let mut st = conn.prepare("insert into fts(fts, rank) values ('merge', -500)")?;
+    st.execute([])?;
+
+    loop {
+        conn.execute("insert into fts(fts, rank) values ('merge', 500)", [])?;
+        let total_changes = get_total_changes()?;
+        let changes = total_changes - last_total_changes;
+        debug!("Modified rows: {changes}");
+        if changes < 2 {
+            break;
+        }
+        last_total_changes = total_changes;
+    }
+
+    Ok(())
+}
+
 fn reindex_fts(tx: &Transaction) -> Result<usize> {
     let mut st = tx.prepare("select rowid, timestamp, source from events order by rowid")?;
     let mut rows = st.query([])?;

src/commands/sqlite/mod.rs

@@ -85,6 +85,12 @@ enum FtsCommand {
         #[arg(value_name = "DB_FILENAME")]
         filename: String,
     },
+
+    /// Optimize FTS data
+    Optimize {
+        #[arg(value_name = "DB_FILENAME")]
+        filename: String,
+    },
 }
 
 #[derive(Debug, Parser)]