# Unable to get any results from IndexStoreDB

**URL:** <https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696>\
**Category:** Source Tooling\
**Tags:** indexstoredb\
**Created:** [December 15, 2019, 11:58am UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696 "2019-12-15T11:58:48Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![ileitch](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/ileitch/32/2095_2.png) [@ileitch](https://forums.swift.org/u/ileitch)\
**Post date:** [December 15, 2019, 11:58am UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/1 "2019-12-15T11:58:48Z")

</div>

Hi all,

I'm trying to use IndexStoreDB to simply read some symbols from the index, however I've been unable to obtain any results at all.

```swift
let storePath = "/Users/ian/code/ileitch/inferno/.build/x86_64-apple-macosx/debug/index/store"
let dbPath = NSTemporaryDirectory() + "db"
let lib = try IndexStoreLibrary(dylibPath: "/Applications/Xcode11.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/libIndexStore.dylib")

let db = try IndexStoreDB(
    storePath: storePath,
    databasePath: dbPath,
    library: lib,
    listenToUnitEvents: false)

```

When I call e.g `db.canonicalOccurrences(ofName: "SomeClass")` it always returns an empty array.

I extended IndexStoreDB to get access to `indexstoredb_index_symbol_names` in an attempt to just list all available symbol names, yet that also returns nothing.

Some things I've tried:

- IndexStoreDB `master` and `switch-5.1-branch` branches
- Using an index store generated by `swift build` and also one generated by Xcode (i.e `DerivedData/App-*/Index/DataStore`)
- Different versions of Xcode - 11.1 and 11.3

I'm sure I must be misunderstanding something pretty fundamental here. Any tips for debugging this?

---

<div class="post-metadata">

**Author:** ![blangmuir](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/blangmuir/32/277_2.png) [@blangmuir](https://forums.swift.org/u/blangmuir)\
**Post date:** [December 16, 2019, 6:06pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/2 "2019-12-16T18:06:33Z")

</div>

> listenToUnitEvents: false)

I'll update the documentation, but this should always be `true` except for during unit tests. If you set this to `false`, you will only get index data when you call `pollForUnitChangesAndWait()` explicitly.

---

<div class="post-metadata">

**Author:** ![ileitch](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/ileitch/32/2095_2.png) [@ileitch](https://forums.swift.org/u/ileitch)\
**Post date:** [December 16, 2019, 6:51pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/3 "2019-12-16T18:51:40Z")

</div>

> [@blangmuir](#):
>
> `pollForUnitChangesAndWait`

Unfortunately changing that hasn't had any affect. The nature of that argument makes me believe I may not be using IndexStoreDB as intended. Is it expected that I can open a pre-built data store? Or is IndexStoreDB only intended for use where a build/indexing happens concurrently while another process listens for events?

I'm simply trying to read `.build/x86_64-apple-macosx/debug/index/store` produced by running `swift build`.

---

<div class="post-metadata">

**Author:** ![blangmuir](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/blangmuir/32/277_2.png) [@blangmuir](https://forums.swift.org/u/blangmuir)\
**Post date:** [December 16, 2019, 7:32pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/4 "2019-12-16T19:32:25Z")

</div>

> [@ileitch](#):
>
> Unfortunately changing that hasn't had any affect.

Ah, there's something else I forgot. Does it work if you sleep a second or two before making the query? Currently it's wired up not to wait for the initial scan of index data. If that's the issue, we have the right hook in the C++ already (`waitUntilDoneInitializing`) and we can provide a way to make the Swift initializer wait if desired.

> [@ileitch](#):
>
> Is it expected that I can open a pre-built data store?

Yes.

> [@ileitch](#):
>
> Or is IndexStoreDB only intended for use where a build/indexing happens concurrently while another process listens for events?

We support both 😸

---

<div class="post-metadata">

**Author:** ![ileitch](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/ileitch/32/2095_2.png) [@ileitch](https://forums.swift.org/u/ileitch)\
**Post date:** [December 16, 2019, 8:08pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/5 "2019-12-16T20:08:24Z")

</div>

> [@blangmuir](#):
>
> Does it work if you sleep a second or two before making the query?

Yep, that was it! Thank you. Exposing `waitUntilDoneInitializing` explicitly or implicitly via the initializer would great.

---

<div class="post-metadata">

**Author:** ![blangmuir](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/blangmuir/32/277_2.png) [@blangmuir](https://forums.swift.org/u/blangmuir)\
**Post date:** [December 16, 2019, 10:03pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/6 "2019-12-16T22:03:24Z")

</div>

[https://github.com/apple/indexstore-db/pull/60](https://github.com/apple/indexstore-db/pull/60)

---

<div class="post-metadata">

**Author:** ![ileitch](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/ileitch/32/2095_2.png) [@ileitch](https://forums.swift.org/u/ileitch)\
**Post date:** [December 19, 2019, 9:33pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/7 "2019-12-19T21:33:49Z")

</div>

I was hoping to use IndexStoreDB to retrieve type information about instance properties, though that information doesn't appear to be exposed in Swift. Does the underlying index actually store type info?

---

<div class="post-metadata">

**Author:** ![blangmuir](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/blangmuir/32/277_2.png) [@blangmuir](https://forums.swift.org/u/blangmuir)\
**Post date:** [December 19, 2019, 9:51pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/8 "2019-12-19T21:51:41Z")

</div>

The USR of a property (and most other declarations) is derived from its mangled name, which contains the (canonical) type. For example,

```swift
public typealias Foo = Int
public var xyx: Foo = 0

```

The index has

```swift
2:12 | variable/Swift | s:1t3xyxSivp | Def | rel: 0
2:17 | type-alias/Swift | s:1t3Fooa | Ref | rel: 0

```

If you take the variable's USR and replace the prefix "s:" with the mangling prefix "$S" you can demangle it:

```bash
$ swift-demangle '$S1t3xyxSivp'
$S1t3xyxSivp ---> t.xyx : Swift.Int

```

which is using the canonical type (`Int` "$SSi") rather than the typealias (`Foo` "$S1t3Fooa").

---

<div class="post-metadata">

**Author:** ![ileitch](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/ileitch/32/2095_2.png) [@ileitch](https://forums.swift.org/u/ileitch)\
**Post date:** [December 19, 2019, 11:10pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/9 "2019-12-19T23:10:52Z")

</div>

Ah yes, of course. Thanks for pointing that out! Now I really wish [[Returned for revision] SE-0262: Demangle function](https://forums.swift.org/t/returned-for-revision-se-0262-demangle-function/28186) had been accepted 😄

Hopefully my last IndexStoreDB question. Is it possible to obtain information about local variables within functions?

---

<div class="post-metadata">

**Author:** ![blangmuir](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/blangmuir/32/277_2.png) [@blangmuir](https://forums.swift.org/u/blangmuir)\
**Post date:** [December 19, 2019, 11:16pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/10 "2019-12-19T23:16:11Z")

</div>

We don't currently index local variables. You could add a new compiler flag to enable that probably (if you search Swift for "indexLocals" you'll see how this would be enabled in the C++ code), but we wouldn't want to index locals by default without being really careful about the performance and space effects. We also haven't tested indexing locals except in narrow circumstances.

---

<div class="post-metadata">

**Author:** ![ileitch](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/ileitch/32/2095_2.png) [@ileitch](https://forums.swift.org/u/ileitch)\
**Post date:** [December 19, 2019, 11:20pm UTC](https://forums.swift.org/t/unable-to-get-any-results-from-indexstoredb/31696/11 "2019-12-19T23:20:21Z")

</div>

OK understood, thanks again.