Indexing and PSI Stubs
The indexing framework allows to access information about files content without loading them to memory and parsing.
Indexes
The indexing framework provides a quick way to locate specific elements, e.g., files containing a certain word or methods with a particular name, in large codebases.
Plugin developers can use the existing indexes built by the IDE itself and build and use their own indexes.
It supports two main types of indexes:
File-based indexes are built directly over the content of files.
Stub indexes are built over serialized stub trees.
A stub tree for a source file is a subset of its PSI tree, which contains only externally visible declarations and is serialized in a compact binary format.
Querying a file-based index gets you the set of files matching a specific condition.
Querying a stub index gets you the set of matching PSI elements.
Therefore, custom language plugin developers typically use stub indexes in their plugin implementations.
Index Viewer plugin can be used to inspect indexes' contents and properties.
Dumb Mode
Indexing is a potentially lengthy process.
It's performed in the background, and during this time, all IDE features are restricted to the ones that don't require indexes: basic text editing, version control, etc.
This restriction is managed by DumbService.
Violations are reported via IndexNotReadyException, see its documentation for information on how to adapt callers.
DumbService provides API to query whether the IDE is currently in "dumb" mode (where index access is not allowed) or "smart" mode (with all index built and ready to use).
It also provides ways of delaying code execution until indexes are ready.
