store: Make write failurs easier to debug

Author: lutter

graph/src/components/store/write.rs

@@ -933,6 +933,17 @@ impl<'a> WriteChunk<'a> {
             count: 0,
         }
     }
+
+    pub fn as_vec(&self) -> Vec<Self> {
+        (0..self.len())
+            .into_iter()
+            .map(|position| WriteChunk {
+                group: self.group,
+                chunk_size: 1,
+                position: self.position + position,
+            })
+            .collect()
+    }
 }
 
 impl<'a> IntoIterator for &WriteChunk<'a> {

store/postgres/src/relational.rs

@@ -767,13 +767,18 @@ impl Layout {
         for chunk in group.write_chunks(chunk_size) {
             // Empty chunks would lead to invalid SQL
             if !chunk.is_empty() {
-                InsertQuery::new(table, &chunk)?
-                    .execute(conn)
-                    .await
-                    .map_err(|e| {
-                        let (block, msg) = chunk_details(&chunk);
-                        StoreError::write_failure(e, table.object.as_str(), block, msg)
-                    })?;
+                if let Err(_) = InsertQuery::new(table, &chunk)?.execute(conn).await {
+                    for single_chunk in chunk.as_vec() {
+                        InsertQuery::new(table, &single_chunk)?
+                            .execute(conn)
+                            .await
+                            .map_err(|e| {
+                                let (block, msg) = chunk_details(&single_chunk);
+                                let msg = format!("{}: offending row {:?}", msg, single_chunk);
+                                StoreError::write_failure(e, table.object.as_str(), block, msg)
+                            })?;
+                    }
+                }
             }
         }
         Ok(())