8000 Docs: Don't reference deprecated `literal` by ftes · Pull Request #4627 · elixir-ecto/ecto · GitHub
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Docs: Don't reference deprecated literal #4627

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Merged
merged 2 commits into from
Jun 23, 2025
Merged

Docs: Don't reference deprecated literal #4627

merged 2 commits into from
Jun 23, 2025

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ftes
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@ftes ftes commented Jun 23, 2025

This is probably not the best fix for the docs.

Additional ideas (not done):

  • use different wording instead of literal
  • reference the identifier and constant function docs
  • explain the difference between identifier and constant

@greg-rychlewski
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Maybe something like this

## Identifiers and Constants

  Sometimes you need to interpolate an identifier or a constant value into a fragment,
  instead of a query parameter. The latter can happen if your database does not allow
  parameterizing certain clauses. For example:

      collation = "es_ES"
      fragment("? COLLATE ?", ^name, ^collation)

      limit = "10"
      "posts" |> select([p], p.title) |> limit(fragment("?", ^limit))

  The first example above won't work because `collation` needs to be quoted as an identifier. 
  The second example won't work on databases that do not allow passing query parameters
  as part of `limit`.

  You can address this by telling Ecto to treat these values differently than a query parameter:

      fragment("? COLLATE ?", ^name, identifier(^collation))
      "posts" |> select([p], p.title) |> limit(fragment("?", ^constant(limit))

  Ecto will make these values directly part of the query, handling quoting and escaping where necessary.

  > #### Query caching {: .warning}
  >
  > Because identifiers and constants are made part of the query, each different
  > value will generate a separate query, with its own cache.

@ftes
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ftes commented Jun 23, 2025

Thanks, I like hour suggestions and copy & pasted them into this PR in case you want to merge.

@greg-rychlewski greg-rychlewski merged commit 18a633a into elixir-ecto:master Jun 23, 2025
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@greg-rychlewski
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thanks for finding this :)

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