Add column name/utility accessors for Legolas.Schema
#52
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Co-authored-by: Alex Arslan <[email protected]>
src/rows.jl
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| Get a tuple with the names of the fields of this `Legolas.Schema`, including names that | ||
| have been inherited from this `Legolas.Schema`'s parent schema. | ||
| """ | ||
| schema_field_names(::Type{S}) where {S<:Schema} = throw(UnknownSchemaError(S())) |
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I actually think the MethodError you'd get from removing this fallback method is more correct than an UnknownSchemaError; it could be that a schema exists (and thus is "known") but a method for schema_field_names simply wasn't defined for it.
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it could be that a schema exists (and thus is "known") but a method for schema_field_names simply wasn't defined for it.
Hmmm how so?
I maybe skimmed too fast but using UnknownSchemaError here seems to be consistent with the other usages of it (and is useful here for the same reason it's useful in those other contexts)
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Hmmm how so?
Very hypothetical case of defining a schema without using @row.
If it's consistent and useful then that's good enough for me.
| print( | ||
| io, | ||
| """ | ||
| encountered unknown `Legolas.Schema` type: $(e.schema) | ||
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| This generally indicates that this schema has not been defined (i.e. | ||
| the schema's corresponding `@row` statement has not been executed) in | ||
| the current Julia session. | ||
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| In practice, this can arise if you try to read a Legolas table with a | ||
| prescribed schema, but haven't actually loaded the schema definition | ||
| (or commonly, haven't loaded the dependency that contains the schema | ||
| definition - check the versions of loaded packages/modules to confirm | ||
| your environment is as expected). | ||
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| Note that if you're in this particular situation, you can still load | ||
| the raw table as-is without Legolas; e.g., to load an Arrow table, call `Arrow.Table(path)`. | ||
| """ | ||
| ) |
| """ | ||
| schema_field_names(::Type{<:Legolas.Schema}) | ||
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| Get a tuple with the names of the fields of this `Legolas.Schema`, including names that | ||
| have been inherited from this `Legolas.Schema`'s parent schema. | ||
| """ | ||
| schema_field_names(s::Schema) = schema_field_names(typeof(s)) | ||
| schema_field_names(::Row{S}) where {S} = schema_field_names(S) | ||
| schema_field_names(::Type{<:Row{S}}) where {S} = schema_field_names(S) | ||
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| """ | ||
| schema_field_types(::Legolas.Schema{name,version}) | ||
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| Get a tuple with the types of the fields of this `Legolas.Schema`, including types of fields that | ||
| have been inherited from this `Legolas.Schema`'s parent schema. | ||
| """ | ||
| schema_field_types(s::Schema) = schema_field_types(typeof(s)) | ||
| schema_field_types(::Row{S}) where {S} = schema_field_types(S) | ||
| schema_field_types(::Type{<:Row{S}}) where {S} = schema_field_types(S) |
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Instead of schema_field_names / schema_field_types, should we define Tables.Schema(::Legolas.Schema) or something similar?
https://tables.juliadata.org/stable/#Tables.Schema is the natural object to use for this purpose in Tables.jl ecosystem IIUC
note that I think Tables.schema(::Vector{<:Legolas.Row})might already "just work" on main (the lowercase schema is a generic accessor). Would be worth checking.
Also we should keep in mind that Legolas Schema fields are explicitly unordered - might be best to call that out in the function docs as well
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superseded by #54 |
This PR addresses #41. It adds two functions:
Tests have been added to make sure these functions behave like we expect.
This includes tests for schema inheritance as well: