Storing ChangeLists and PatchSets in Firestore

We need to keep track of the ChangeLists and PatchSets that have been associated with TryJob data that we have ingested.

See https://docs.google.com/document/d/1d0tOhgx51QOGiSXqTxiwNSlgm1pYHTUSBK3agysX6Iw/edit for more context.

Schema

We should have two Firestore Collections (i.e. tables), one for ChangeList and a subcollection for PatchSet.

ChangeList
	ID         string  # SystemID + System
	SystemID   string  # The id of the CL in, for example, Gerrit
	System     string  # "gerrit", "github", etc
	Status     int     # corresponds to code_review.CLStatus
	Owner      string  # email address
	Updated    time.Time
	Subject    string
	[]PatchSet
		SystemID            string  # The id of the PS in, for example, Gerrit
		System              string  # "gerrit", "github", etc
		ChangeListID        string  # SystemID from ChangeList
		Order               int     # number of this PS
		GitHash             string
		HasUntriagedDigests bool
		CommentedOnCL       bool

Indexing

We need the following composite indexes:

Collection ID | Fields

clstore_changelist | status: ASC updated: DESC

We should mark ChangeList.Subject as no-index, to save some index space. https://cloud.google.com/firestore/docs/query-data/indexing#exemptions

Usage

We'll be querying:

• ChangeLists by SystemID, System
• PatchSets belonging to a ChangeList ordered by Order.

With this hierarchical setup, we should avoid conflicts between multiple systems.

Growth Opportunities

We could open up the searching to include “get only Open CLs” or get CLs by a given (the logged in?) user. This should just entail adding some more indices and a few new functions to the API.