new option 'query'.

README.md

@@ -115,6 +115,7 @@ transformer({
 - `targetIndexName`: The target Elasticsearch index where documents will be indexed.
 - `mappings`: Optional Elasticsearch document mappings. If not set and you're reindexing from another index, the mappings from the existing index will be used.
 - `mappingsOverride`: If you're reindexing and this is set to `true`, `mappings` will be applied on top of the source index's mappings. Defaults to `false`.
+- `query`: Optional Elasticsearch [DSL query](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl.html) to filter documents from the source index.
 - `skipHeader`: If true, skips the first line of the source file. Defaults to `false`.
 - `transform(line)`: A callback function which allows the transformation of a source line into one or several documents.
 - `verbose`: Logging verbosity, defaults to `true`

src/_index-reader.js

@@ -5,7 +5,7 @@ const MAX_QUEUE_SIZE = 5;
 // create a new progress bar instance and use shades_classic theme
 const progressBar = new cliProgress.SingleBar({}, cliProgress.Presets.shades_classic);
 
-export default function indexReaderFactory(indexer, sourceIndexName, transform, client) {
+export default function indexReaderFactory(indexer, sourceIndexName, transform, client, query) {
   return async function indexReader() {
     const responseQueue = [];
     let docsNum = 0;
@@ -15,6 +15,7 @@ export default function indexReaderFactory(indexer, sourceIndexName, transform,
         index: sourceIndexName,
         scroll: '30s',
         size: 10000,
+        query,
       });
     }
 

src/main.js

@@ -16,6 +16,7 @@ export default async function transformer({
   targetIndexName,
   mappings,
   mappingsOverride = false,
+  query,
   skipHeader = false,
   transform,
   verbose = true,
@@ -83,6 +84,7 @@ export default async function transformer({
         sourceIndexName,
         transform,
         sourceClient,
+        query,
       );
     }