Other than that, it should beĮquivalent to a built-in Ecto query function. The only downside is that it will show up as a fragment when To have coalesce/2 available, just import the module that defines it. To expose SQL's coalesce function you can define this macro: defmodule CustomFunctions do defmacro coalesce ( left, right ) do quote do fragment ( "coalesce(?, ?)", unquote ( left ), unquote ( right ) ) end end end You can add a custom Ecto query function using macros. Literal will generate a separate query, with its own cache.ĭefining custom functions using macros and fragment Literals and query cachingīecause literals are made part of the query, each interpolated You can address this by telling Ecto that variable is a literal: fragment ( "? COLLATE ?", ^ name, literal ( ^ collation ) )Įcto will then escape it and make it part of the query. The example above won't work because collation will be passedĪs a parameter, while it has to be a literal part of the query. Name or a collation, such as: collation = "es_ES" fragment ( "? COLLATE ?", ^ name, ^ collation ) For example, you may need to pass a table Sometimes you need to interpolate a literal value into a fragment, To explicitly cast parameters via type/2: fragment ( "lower(?)", p. It is very important to keep in mind that Ecto is unable to do any In the example above, we are using the lower procedure in the If the literal character ? is required as part of theįragment, it can be escaped with \\? (one escape for strings, title ) = ^ title endĮvery occurrence of the ? character will be interpreted as a placeįor parameters, which must be given as additional arguments toįragment. published_at ) and fragment ( "lower(?)", p. When such is required, it is possible to useįragments to send any expression to the database: def unpublished_by_title ( title ) do from p in Post, where : is_nil ( p. It is not possible to represent all possible database queries usingĮcto's query syntax. Link to this function fragment(fragments) View Source Interval in PostgreSQL), it should work just fine in Ecto To use them in a certain way (like adding a date and an The Ecto implementation of these operators provide onlyĪ thin layer above the adapters. "week", "day", "hour", "minute", "second", "millisecond", andĭate/ Time functions like datetime_add/3, date_add/3, from_now/2,Įcto also supports many of the windows functions found Use them in Ecto queries (see docs for fragment/1).Įcto supports following values for interval option: "year", "month", Purposes and one should never need to invoke them directly.įurthermore, it is possible to define your own macros and Note the functions in this module exist for documentation General: fragment/1, field/2, type/2, as/1, parent_as/1, selected_as/1.Inside select: struct/2, map/2, merge/2, selected_as/2 and literals (map, tuples, lists, etc).Date/time intervals: datetime_add/3, date_add/3, from_now/2, ago/2. Subquery operators: any, all and exists.Lists all functions allowed in the query API.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |