sqlite: remove the null prototype from result rows

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#65,799 4 comments 1 reaction 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Active
Tech stack
javascript, sqlite
Domain
backend, databases

Research direction

Start by locating the implementations of get(), all(), iterate(), and the existing run() result handling, then read how the V8 API and v8::DictionaryTemplate are used. Review the proposed benchmarks and working implementation mentioned in the issue. Done means evaluating the ordinary-object behavior, shared row shape, performance, and semver-major compatibility concerns.

Written by the indexing model from the issue text.

Description

Current behavior

Rows returned by get(), all() and iterate() are created with a null prototype. The V8 API that does this produces dictionary-mode objects, and V8 will not cache a prototype transition on a dictionary map, so every row also gets its own freshly allocated hidden class. Rows from the same statement therefore share no shape: they are slow to build, and every property access on them in user code is megamorphic.

Proposal

Drop the null prototype and build rows with v8::DictionaryTemplate, cached per statement. Rows become ordinary objects, and every row of a statement shares one hidden class.

Pros

  • all() is 10–37% faster depending on the query; reading the rows afterwards is far cheaper still.
  • Consistent with run(), which already returns an ordinary object, and with better-sqlite3.

Cons

  • Semver-major.
  • Rows can no longer be indexed by untrusted keys without Object.hasOwn() — row.toString and row.constructor start resolving through Object.prototype.
  • User code comparing rows against { __proto__: null, ... } breaks.

Prototype pollution is not a concern either way: rows are built by defining own properties directly, so a __proto__ column is an own property and never reaches Object.prototype.

I have benchmarks and a working implementation if there is interest.

Dominant language
JavaScript
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Forks
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Avg merge
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Merged PRs (30d)
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