optionally use unsafe SQLite optimisations during initial loading

src/api_test.rs

@@ -14,7 +14,15 @@ use sqlx::{
 use std::str::FromStr;
 
 pub async fn run_api_tests(table: &str, database: &str) -> Result<(), sqlx::Error> {
-    let config = valve(table, database, &ValveCommand::Config, false, "table").await?;
+    let config = valve(
+        table,
+        database,
+        &ValveCommand::Config,
+        false,
+        false,
+        "table",
+    )
+    .await?;
     let config: SerdeValue = serde_json::from_str(config.as_str()).unwrap();
     let config = config.as_object().unwrap();
 

src/lib.rs

@@ -982,12 +982,16 @@ pub enum ValveCommand {
 /// optionally create and/or load it according to the value of `command` (see [ValveCommand]).
 /// If the `verbose` flag is set to true, output status messages while loading. If `config_table`
 /// is given and `table_table` indicates a database, query the table called `config_table` for the
-/// table table information. Returns the configuration map as a String.
+/// table table information. Returns the configuration map as a String. If `initial_load` is set to
+/// true, then (SQLite only) the database settings will be tuned for initial loading. Note that
+/// these settings are unsafe and should be used for initial loading only, as data integrity will
+/// not be guaranteed in the case of an interrupted transaction.
 pub async fn valve(
     table_table: &str,
     database: &str,
     command: &ValveCommand,
     verbose: bool,
+    initial_load: bool,
     config_table: &str,
 ) -> Result<String, sqlx::Error> {
     let parser = StartParser::new();
@@ -1025,6 +1029,20 @@ pub async fn valve(
         sqlx_query("PRAGMA foreign_keys = ON")
             .execute(&pool)
             .await?;
+        if initial_load {
+            // These pragmas are unsafe but they are used during initial loading since data
+            // integrity is not a priority in this case.
+            sqlx_query("PRAGMA journal_mode = OFF")
+                .execute(&pool)
+                .await?;
+            sqlx_query("PRAGMA synchronous = 0").execute(&pool).await?;
+            sqlx_query("PRAGMA cache_size = 1000000")
+                .execute(&pool)
+                .await?;
+            sqlx_query("PRAGMA temp_store = MEMORY")
+                .execute(&pool)
+                .await?;
+        }
     }
 
     let (sorted_table_list, constraints_config) = configure_db(

src/main.rs

@@ -22,6 +22,7 @@ async fn main() -> Result<(), sqlx::Error> {
     let mut create_only = false;
     let mut config_table = String::new();
     let mut verbose = false;
+    let mut initial_load = false;
     let mut source = String::new();
     let mut destination = String::new();
 
@@ -65,6 +66,14 @@ async fn main() -> Result<(), sqlx::Error> {
             r#"Write the SQL used to create the database to stdout after configuring it, and then
                while loading the database, write progress messages to stderr."#,
         );
+        ap.refer(&mut initial_load).add_option(
+            &["--initial_load"],
+            StoreTrue,
+            r#"(SQLite only) When this flag is set, the database settings will be tuned for initial
+               loading. Note that these settings are unsafe and should be used for initial loading
+               only, as data integrity will not be guaranteed in the case of an interrupted
+               transaction."#,
+        );
         ap.refer(&mut source).add_argument(
             "SOURCE",
             Store,
@@ -109,6 +118,7 @@ async fn main() -> Result<(), sqlx::Error> {
             &String::from(":memory:"),
             &ValveCommand::Config,
             false,
+            false,
             &config_table,
         )
         .await?;
@@ -141,6 +151,7 @@ async fn main() -> Result<(), sqlx::Error> {
             &destination,
             &ValveCommand::Create,
             verbose,
+            false,
             &config_table,
         )
         .await?;
@@ -150,6 +161,7 @@ async fn main() -> Result<(), sqlx::Error> {
             &destination,
             &ValveCommand::Load,
             verbose,
+            initial_load,
             &config_table,
         )
         .await?;