store: Better error message for missing template during grafting

store/postgres/src/copy.rs

@@ -748,15 +748,21 @@ impl Connection {
         self.conn.transaction(|conn| f(conn))
     }
 
+    /// Copy private data sources if the source uses a schema version that
+    /// has a private data sources table. The copying is done in its own
+    /// transaction.
     fn copy_private_data_sources(&mut self, state: &CopyState) -> Result<(), StoreError> {
         if state.src.site.schema_version.private_data_sources() {
-            DataSourcesTable::new(state.src.site.namespace.clone()).copy_to(
-                &mut self.conn,
-                &DataSourcesTable::new(state.dst.site.namespace.clone()),
-                state.target_block.number,
-                &self.src_manifest_idx_and_name,
-                &self.dst_manifest_idx_and_name,
-            )?;
+            let conn = &mut self.conn;
+            conn.transaction(|conn| {
+                DataSourcesTable::new(state.src.site.namespace.clone()).copy_to(
+                    conn,
+                    &DataSourcesTable::new(state.dst.site.namespace.clone()),
+                    state.target_block.number,
+                    &self.src_manifest_idx_and_name,
+                    &self.dst_manifest_idx_and_name,
+                )
+            })?;
         }
         Ok(())
     }

store/postgres/src/dynds/private.rs

@@ -9,7 +9,7 @@ use diesel::{
 };
 
 use graph::{
-    anyhow::Context,
+    anyhow::{anyhow, Context},
     components::store::{write, StoredDynamicDataSource},
     constraint_violation,
     data_source::CausalityRegion,
@@ -258,12 +258,24 @@ impl DataSourcesTable {
             let name = &src_manifest_idx_and_name
                 .iter()
                 .find(|(idx, _)| idx == &src_manifest_idx)
-                .context("manifest_idx not found in src")?
+                .with_context(|| {
+                    anyhow!(
+                        "the source {} does not have a template with index {}",
+                        self.namespace,
+                        src_manifest_idx
+                    )
+                })?
                 .1;
             let dst_manifest_idx = dst_manifest_idx_and_name
                 .iter()
                 .find(|(_, n)| n == name)
-                .context("name not found in dst")?
+                .with_context(|| {
+                    anyhow!(
+                        "the destination {} is missing a template with name {}. The source {} created one at block {:?}",
+                        dst.namespace,
+                        name, self.namespace, block_range.0
+                    )
+                })?
                 .0;
 
             let query = format!(