Search indexing (Code and Work Item) works in 2 phases:
- Bulk Indexing (BI) where the entire code and work item artifacts in all projects/repositories under a Collection are indexed. This is a time consuming operation and depends on the size of the artifacts under the collection.
- Continuous Indexing (CI) which handles all incremental updates to the artifacts (add/updated/delete) and indexes them. This is notification based model where the indexer listens to TFS events and operates based on those event notifications. CI handles almost all update operations including CRUD operations at Project/Repository/Collection layer (such as Repository renames, Project add/deletes, etc.). The operation time for these CI would depend again on the size of the incremental update. BI always precedes CI i.e. a CI will never execute on a project/repository until BI is completed for the same.
In addition to this, Search indexer has in-built resilience measures to monitor and run patch operations for any missed notifications and/or any other reason where the index is not up-to-date with the actual state of artifacts in TFS. These patch operations run at specific intervals (typically every 12 hours duration) on each Collection.
Keeping the above background information in mind, in most occasion one would never need to run a BI operation (i.e. Re-Index) on a Collection. However there are certain instances planned/unplanned where it will require a re-indexing. This can happen for various reasons such as -
- Index shard corruptions which are not auto-recovered from the indexer. Any such index level errors would required a clean re-indexing.
- Manually/accidentally deleted index data folder entirely (or specific index folders within it). Indexer does not auto-recover from such actions.
- Planning to move the index into another machine, let's say as part of an upgrade. In this case, the configuration upgrade step does take care of re-indexing internally, but the point is, re-indexing does happen.
- Search query shows stale results. Could be because of some consistent error, or the BI has simply aborted/crashed. And now, it requires a full re-indexing of that collection.
Coming to the crux of this post, how to do a clean re-indexing? This applies to both Code as well as Work Item search.
Clean-up Index Data and Re-index
This applies to scenarios such as  &  listed above where there are index level errors and the index needs to be re-built.
- Pause Indexing for all collections. Run the following script on TFS Configuration DB
- Login to the machine where the Elasticsearch (ES) is running
- Stop the ES service
- Delete the entire Search Index folder (something like, C:\TfsData\Search\IndexStore, or wherever you had configured it to be)
- Restart the TFS Job Agent service(s) on the AT machines
- Delete the following tables from each of the collection DBs
DELETE FROM [Search].[tbl_IndexingUnit]
DELETE FROM [Search].[tbl_IndexingUnitChangeEvent]
DELETE FROM [Search].[tbl_IndexingUnitChangeEventArchive]
DELETE FROM [Search].[tbl_JobYield]
DELETE FROM [Search].[tbl_TreeStore]
DELETE FROM [Search].[tbl_DisabledFiles]
DELETE FROM [Search].[tbl_ResourceLockTable]
- Restart the ES service
- Run this script on TFS Configuration DB: https://github.com/Microsoft/Code-Search/blob/master/ResumeIndexing.ps1
- Run this script (pick from the correct TFS release folder) on each of the collections: https://github.com/Microsoft/Code-Search/blob/master/TFS_2017Update2/MissingIndexFolderTriggerCollectionIndexing.ps1
Try the last script on a smaller collection first (which has less number of repositories) so that you can verify that indexing happened correctly and the results are query-able.
Re-index at Collection level
This applies to scenario where the index configuration and health is good; however the search results are not as expected and you need to refresh the index for this specific collection (something in the lines of scenario  above).
There are 2 approaches to re-indexing here:
(A) Extension Uninstall and Install
- From the extension management page in TFS portal, uninstall the specific extension (Code or Work Item, or both depending on which entity's index you want to refresh) for the collection.
- Wait for 10-15 min for the index to be cleaned up. The extension uninstall triggers a sequence of clean up jobs per repository under that collection to delete the indices.
In the [Tfs_Configuration].[dbo].[tbl_JobHistory] table, you can see delete jobs cleaning up the ES documents. There will be one job result entry for each repository in that collection.
WHERE ResultMessage like '%Delete-SearchExtensionEventNotification%'
ORDER BY StartTime desc
[The manual wait step only applies to TFS 2017 Update 2 and earlier. It will not be required for next TFS major release. The synchronization is now built into the indexer pipeline]
- Install the specific extension for the collection.
Depending on the code/work item volume in the collection, the re-indexing will take it's time. To monitor the indexing progress, check the blog post here.
(B) Collection re-indexing through script.
- Run this script: https://github.com/Microsoft/Code-Search/blob/master/TFS_2017Update2/TriggerCollectionIndexing.ps1
- To monitor the indexing progress, check the blog post here.
Re-index at Repository level
This applies to the scenario where the index configuration and health is good; however the search results are not as expected for some specific repository and you need to refresh the index for this repository (something in the lines of scenario  above). Currently this applies to Code Search only.
- Run this script: https://github.com/Microsoft/Code-Search/blob/master/TFS_2017Update2/Re-IndexingCodeRepository.ps1
- To monitor the indexing progress, check the blog post here.
Couple of important points related to re-indexing of collection/repository -
- Bulk indexing is a costly operation. Depending on the volume of code/work item data in the collection, it might take from few min. to few days. Hence, in case of search query returning stale data, it's advisable to wait for 12-24 hours for the indexer's scheduled patch operation to execute and auto-patch the index.
- For all scripts, do ensure you are picking up the correct version from the appropriate TFS release folder