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fix(firestore): fetch large documents in chunks from local SQLite cache - #8362

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dlarocque merged 3 commits into
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dl/sqlite-large-docs-chunks
Jun 29, 2026
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fix(firestore): fetch large documents in chunks from local SQLite cache#8362
dlarocque merged 3 commits into
mainfrom
dl/sqlite-large-docs-chunks

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@dlarocque
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The SDK can store large documents in the cache, but it cannot read them back into memory because SQLite's CursorWindow has a 2MB row read limit. This change works around that limitation by reading large rows in chunks using SUBSTR.

The goal is to support reading 16MB documents from the cache.

Notes:

  • Reading a 16MB document with this takes ~250ms in my testing in the emulators, which is slow.
  • Does not impact latency for cache reads that are below 1MB
  • Alternatives considered: migrating to different SQLite library (high effort), read/write large documents directly in the filesystem (complex).

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dlarocque requested a review from wu-hui June 25, 2026 15:42
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📝 PRs merging into main branch

Our main branch should always be in a releasable state. If you are working on a larger change, or if you don't want this change to see the light of the day just yet, consider using a feature branch first, and only merge into the main branch when the code complete and ready to be released.

wu-hui
wu-hui previously approved these changes Jun 26, 2026
@dlarocque
dlarocque merged commit f521ece into main Jun 29, 2026
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@dlarocque
dlarocque deleted the dl/sqlite-large-docs-chunks branch June 29, 2026 20:04
kmandrika pushed a commit that referenced this pull request Jun 30, 2026
…he (#8362)

The SDK can store large documents in the cache, but it cannot read them
back into memory because SQLite's `CursorWindow` has a 2MB row read
limit. This change works around that limitation by reading large rows in
chunks using `SUBSTR`.

The goal is to support reading 16MB documents from the cache.

Notes:
- Reading a 16MB document with this takes ~250ms in my testing in the
emulators, which is slow.
- Does not impact latency for cache reads that are below 1MB
- Alternatives considered: migrating to different SQLite library (high
effort), read/write large documents directly in the filesystem
(complex).
@firebase firebase locked and limited conversation to collaborators Jul 30, 2026
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