Note: This blog post strays away from our usual focus on tips & tricks. It does not provide a solution or workaround for Mail searches on macOS Catalina. It rather discusses technical background and ethical considerations.
Spotlight vs. Core Spotlight
Recent versions of macOS use two indexing technologies to power local searches in the Spotlight window: Spotlight and Core Spotlight.
Spotlight was introduced with OS X 10.4 Tiger. It indexes user files. Whenever a file is modified, the Spotlight engine calls upon the appropriate importer plug-in to read metadata and text content from the file. That data is then indexed for searching.
The fact that Spotlight works only with files can be a problem for some applications. For “shoebox” applications, it is often more natural to store data items in a single file or database rather than use one file per data item. Such data items cannot be indexed by Spotlight. Thus such applications either have to change their data storage to fit Spotlight’s requirements or resort to tricks to get their data into Spotlight.
Core Spotlight is a more recent addition. Core Spotlight does not watch for data or files to appear. Instead, applications actively submit data to Core Spotlight for indexing. This reversal of roles allows Core Spotlight to index any kind of data. Continue reading Mail Search on MacOS Catalina