Refactor view management

Author: simolus3

crates/core/src/lib.rs

@@ -64,7 +64,6 @@ fn init_extension(db: *mut sqlite::sqlite3) -> Result<(), PowerSyncError> {
     let state = Rc::new(DatabaseState::new());
 
     crate::version::register(db)?;
-    crate::views::register(db)?;
     crate::uuid::register(db)?;
     crate::diff::register(db)?;
     crate::fix_data::register(db)?;

crates/core/src/migrations.rs

@@ -10,6 +10,7 @@ use sqlite::ResultCode;
 
 use crate::error::{PSResult, PowerSyncError};
 use crate::fix_data::apply_v035_fix;
+use crate::schema::inspection::ExistingView;
 use crate::sync::BucketPriority;
 
 pub const LATEST_VERSION: i32 = 11;
@@ -188,15 +189,19 @@ VALUES(4,
         // Down migrations are less common, so we're okay about that breaking
         // in some cases.
 
+        for mut view in ExistingView::list(local_db)? {
+            view.delete_trigger_sql = String::default();
+            view.update_trigger_sql = String::default();
+            view.insert_trigger_sql = String::default();
+
+            // This drops everything, but immediately re-creates the CREATE VIEW statement.
+            view.create(local_db)?;
+        }
+
         // language=SQLite
         local_db
           .exec_safe(
               "\
-UPDATE powersync_views SET
-        delete_trigger_sql = '',
-        update_trigger_sql = '',
-        insert_trigger_sql = '';
-
 ALTER TABLE ps_buckets RENAME TO ps_buckets_old;
 ALTER TABLE ps_oplog RENAME TO ps_oplog_old;
 

crates/core/src/schema/inspection.rs

@@ -0,0 +1,81 @@
+use alloc::borrow::ToOwned;
+use alloc::{format, vec};
+use alloc::{string::String, vec::Vec};
+use powersync_sqlite_nostd::Connection;
+use powersync_sqlite_nostd::{self as sqlite, ResultCode};
+
+use crate::error::{PSResult, PowerSyncError};
+use crate::util::quote_identifier;
+
+/// An existing PowerSync-managed view that was found in the schema.
+#[derive(PartialEq)]
+pub struct ExistingView {
+    /// The name of the view itself.
+    pub name: String,
+    /// SQL contents of the `CREATE VIEW` statement.
+    pub sql: String,
+    /// SQL contents of all triggers implementing deletes by forwarding to
+    /// `ps_data` and `ps_crud`.
+    pub delete_trigger_sql: String,
+    /// SQL contents of the trigger implementing inserts on this view.
+    pub insert_trigger_sql: String,
+    /// SQL contents of the trigger implementing updates on this view.
+    pub update_trigger_sql: String,
+}
+
+impl ExistingView {
+    pub fn list(db: *mut sqlite::sqlite3) -> Result<Vec<Self>, PowerSyncError> {
+        let mut results = vec![];
+        let stmt = db.prepare_v2("
+SELECT
+    view.name,
+    view.sql,
+    ifnull(group_concat(trigger1.sql, ';\n' ORDER BY trigger1.name DESC), ''),
+    ifnull(trigger2.sql, ''),
+    ifnull(trigger3.sql, '')
+    FROM sqlite_master view
+    LEFT JOIN sqlite_master trigger1
+        ON trigger1.tbl_name = view.name AND trigger1.type = 'trigger' AND trigger1.name GLOB 'ps_view_delete*'
+    LEFT JOIN sqlite_master trigger2
+        ON trigger2.tbl_name = view.name AND trigger2.type = 'trigger' AND trigger2.name GLOB 'ps_view_insert*'
+    LEFT JOIN sqlite_master trigger3
+        ON trigger3.tbl_name = view.name AND trigger3.type = 'trigger' AND trigger3.name GLOB 'ps_view_update*'
+    WHERE view.type = 'view' AND view.sql GLOB  '*-- powersync-auto-generated'
+    GROUP BY view.name;
+        ").into_db_result(db)?;
+
+        while stmt.step()? == ResultCode::ROW {
+            let name = stmt.column_text(0)?.to_owned();
+            let sql = stmt.column_text(1)?.to_owned();
+            let delete = stmt.column_text(2)?.to_owned();
+            let insert = stmt.column_text(3)?.to_owned();
+            let update = stmt.column_text(4)?.to_owned();
+
+            results.push(ExistingView {
+                name,
+                sql,
+                delete_trigger_sql: delete,
+                insert_trigger_sql: insert,
+                update_trigger_sql: update,
+            });
+        }
+
+        Ok(results)
+    }
+
+    pub fn drop_by_name(db: *mut sqlite::sqlite3, name: &str) -> Result<(), PowerSyncError> {
+        let q = format!("DROP VIEW IF EXISTS {:}", quote_identifier(name));
+        db.exec_safe(&q)?;
+        Ok(())
+    }
+
+    pub fn create(&self, db: *mut sqlite::sqlite3) -> Result<(), PowerSyncError> {
+        Self::drop_by_name(db, &self.name)?;
+        db.exec_safe(&self.sql).into_db_result(db)?;
+        db.exec_safe(&self.delete_trigger_sql).into_db_result(db)?;
+        db.exec_safe(&self.insert_trigger_sql).into_db_result(db)?;
+        db.exec_safe(&self.update_trigger_sql).into_db_result(db)?;
+
+        Ok(())
+    }
+}

crates/core/src/schema/management.rs

@@ -1,5 +1,7 @@
 extern crate alloc;
 
+use alloc::borrow::ToOwned;
+use alloc::collections::btree_map::BTreeMap;
 use alloc::rc::Rc;
 use alloc::string::String;
 use alloc::vec::Vec;
@@ -12,8 +14,13 @@ use sqlite::{Connection, ResultCode, Value};
 
 use crate::error::{PSResult, PowerSyncError};
 use crate::ext::ExtendedDatabase;
+use crate::schema::inspection::ExistingView;
 use crate::state::DatabaseState;
 use crate::util::{quote_identifier, quote_json_path};
+use crate::views::{
+    powersync_trigger_delete_sql, powersync_trigger_insert_sql, powersync_trigger_update_sql,
+    powersync_view_sql,
+};
 use crate::{create_auto_tx_function, create_sqlite_text_fn};
 
 use super::Schema;
@@ -236,55 +243,46 @@ SELECT
     Ok(())
 }
 
-fn update_views(db: *mut sqlite::sqlite3, schema: &str) -> Result<(), PowerSyncError> {
-    // Update existing views if modified
-    // language=SQLite
-    db.exec_text("\
-UPDATE powersync_views SET
-sql = gen.sql,
-delete_trigger_sql = gen.delete_trigger_sql,
-insert_trigger_sql = gen.insert_trigger_sql,
-update_trigger_sql = gen.update_trigger_sql
-FROM (SELECT
-      ifnull(json_extract(json_each.value, '$.view_name'), json_extract(json_each.value, '$.name')) as name,
-                   powersync_view_sql(json_each.value) as sql,
-                   powersync_trigger_delete_sql(json_each.value) as delete_trigger_sql,
-                   powersync_trigger_insert_sql(json_each.value) as insert_trigger_sql,
-                   powersync_trigger_update_sql(json_each.value) as update_trigger_sql
-                   FROM json_each(json_extract(?, '$.tables'))) as gen
-                   WHERE powersync_views.name = gen.name AND
-                       (powersync_views.sql IS NOT gen.sql OR
-                        powersync_views.delete_trigger_sql IS NOT gen.delete_trigger_sql OR
-                        powersync_views.insert_trigger_sql IS NOT gen.insert_trigger_sql OR
-                        powersync_views.update_trigger_sql IS NOT gen.update_trigger_sql)
-    ", schema).into_db_result(db)?;
-
-    // Create new views
-    // language=SQLite
-    db.exec_text("\
-INSERT INTO powersync_views(
-    name,
-    sql,
-    delete_trigger_sql,
-    insert_trigger_sql,
-    update_trigger_sql
-)
-SELECT
-ifnull(json_extract(json_each.value, '$.view_name'), json_extract(json_each.value, '$.name')) as name,
-             powersync_view_sql(json_each.value) as sql,
-             powersync_trigger_delete_sql(json_each.value) as delete_trigger_sql,
-             powersync_trigger_insert_sql(json_each.value) as insert_trigger_sql,
-             powersync_trigger_update_sql(json_each.value) as update_trigger_sql
-             FROM json_each(json_extract(?, '$.tables'))
-                            WHERE name NOT IN (SELECT name FROM powersync_views)", schema).into_db_result(db)?;
-
-    // Delete old views
-    // language=SQLite
-    db.exec_text("\
-DELETE FROM powersync_views WHERE name NOT IN (
-    SELECT ifnull(json_extract(json_each.value, '$.view_name'), json_extract(json_each.value, '$.name'))
-                        FROM json_each(json_extract(?, '$.tables'))
-            )", schema).into_db_result(db)?;
+fn update_views(db: *mut sqlite::sqlite3, schema: &Schema) -> Result<(), PowerSyncError> {
+    // First, find all existing views and index them by name.
+    let existing = ExistingView::list(db)?;
+    let mut existing = {
+        let mut map = BTreeMap::new();
+        for entry in &existing {
+            map.insert(&*entry.name, entry);
+        }
+        map
+    };
+
+    for table in &schema.tables {
+        let view_sql = powersync_view_sql(table);
+        let delete_trigger_sql = powersync_trigger_delete_sql(table)?;
+        let insert_trigger_sql = powersync_trigger_insert_sql(table)?;
+        let update_trigger_sql = powersync_trigger_update_sql(table)?;
+
+        let wanted_view = ExistingView {
+            name: table.view_name().to_owned(),
+            sql: view_sql,
+            delete_trigger_sql,
+            insert_trigger_sql,
+            update_trigger_sql,
+        };
+
+        if let Some(actual_view) = existing.remove(table.view_name()) {
+            if *actual_view == wanted_view {
+                // View exists with identical definition, don't re-create.
+                continue;
+            }
+        }
+
+        // View does not exist or has been defined differently, re-create.
+        wanted_view.create(db)?;
+    }
+
+    // Delete old views.
+    for remaining in existing.values() {
+        ExistingView::drop_by_name(db, &remaining.name)?;
+    }
 
     Ok(())
 }
@@ -309,7 +307,7 @@ fn powersync_replace_schema_impl(
 
     update_tables(db, schema)?;
     update_indexes(db, &parsed_schema)?;
-    update_views(db, schema)?;
+    update_views(db, &parsed_schema)?;
 
     state.set_schema(parsed_schema);
     Ok(String::from(""))

crates/core/src/schema/mod.rs

@@ -1,3 +1,4 @@
+pub mod inspection;
 mod management;
 mod table_info;
 

crates/core/src/schema/table_info.rs

@@ -29,10 +29,6 @@ pub struct RawTable {
 }
 
 impl Table {
-    pub fn from_json(text: &str) -> Result<Self, serde_json::Error> {
-        serde_json::from_str(text)
-    }
-
     pub fn view_name(&self) -> &str {
         self.view_name_override
             .as_deref()