Add spill to disk setting doc

src/content/docs/cypher/configuration.md

@@ -20,6 +20,7 @@ configuration **cannot** be used with other query clauses, such as `RETURN`.
 | `PROGRESS_BAR_TIME` | show progress bar after time in ms                                             | 1000                   |
 | `CHECKPOINT_THRESHOLD` | the WAL size threshold in bytes at which to automatically trigger a checkpoint | 16777216 (16MB)        |
 | `WARNING_LIMIT` | The maximum number of warnings that can be stored in a single connection | 8192        |
+| `SPILL_TO_DISK_TMP_FILE` | The location of the temporary file to use to store data if there is not enough memory during a copy | `copy.tmp` inside the database directory |
 
 ### Database configuration
 | Option | Description | Default |
@@ -74,3 +75,10 @@ CALL checkpoint_threshold=16777216;
 ```cypher
 CALL warning_limit=1024;
 ```
+
+#### Configure Spill to disk temporary file
+```cypher
+CALL spill_to_disk_tmp_file="/path/to/tmp/file";
+# Disables spilling to disk
+CALL spill_to_disk_tmp_file="";
+```

src/content/docs/import/index.mdx

@@ -112,3 +112,15 @@ The above approach only works when the input data source contains *fewer* column
 node table being copied into. If the node table had fewer columns than the data source, it would
 lead to a Runtime error because of a column number mismatch.
 :::
+
+## Importing large REL tables
+
+Importing large REL tables can use significant amounts of memory. If the memory used to prepare the
+imported REL table data comes close to exceeding the buffer pool size,
+Kùzu will spill some of this data to a `copy.tmp` file in the database directory.
+The location of this file can be customized using the
+[`spill_to_disk_tmp_file`](/cypher/configuration#configure-spill-to-disk-temporary-file) setting.
+You can also disable spilling to disk by setting `spill_to_disk_tmp_file` to an empty string.
+
+This feature is disabled by default for in-memory databases and databases using file system extensions,
+but can be enabled for these cases by setting a custom `spill_to_disk_tmp_file` path.