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Add strict mode for more type-stable results if desired #304

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Merged
quinnj merged 1 commit into from
Nov 29, 2022
Merged

Add strict mode for more type-stable results if desired #304

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25 changes: 15 additions & 10 deletions src/tables.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ using Tables

sym(ptr) = ccall(:jl_symbol, Ref{Symbol}, (Ptr{UInt8},), ptr)

struct Query
struct Query{strict}
stmt::Stmt
status::Base.RefValue{Cint}
names::Vector{Symbol}
Expand All @@ -14,14 +14,14 @@ end
# check if the query has no (more) rows
Base.isempty(q::Query) = q.status[] == C.SQLITE_DONE

struct Row <: Tables.AbstractRow
q::Query
struct Row{strict} <: Tables.AbstractRow
q::Query{strict}
rownumber::Int
end

getquery(r::Row) = getfield(r, :q)

Tables.isrowtable(::Type{Query}) = true
Tables.isrowtable(::Type{<:Query}) = true
Tables.columnnames(q::Query) = q.names

struct DBTable
Expand All @@ -37,17 +37,17 @@ Tables.istable(::Type{<:DBTables}) = true
Tables.rowaccess(::Type{<:DBTables}) = true
Tables.rows(dbtbl::DBTables) = dbtbl

function Tables.schema(q::Query)
if isempty(q)
# when the query is empty, return the types provided by SQLite
function Tables.schema(q::Query{strict}) where {strict}
if isempty(q) || strict
# when the query is empty or types are strict, return the types provided by SQLite
# by default SQLite.jl assumes all columns can have missing values
Tables.Schema(Tables.columnnames(q), q.types)
else
return nothing # fallback to the actual column types of the result
end
end

Base.IteratorSize(::Type{Query}) = Base.SizeUnknown()
Base.IteratorSize(::Type{<:Query}) = Base.SizeUnknown()
Base.eltype(q::Query) = Row

function reset!(q::Query)
Expand Down Expand Up @@ -77,12 +77,14 @@ end
)
end

function getvalue(q::Query, col::Int, rownumber::Int, ::Type{T}) where {T}
function getvalue(q::Query{strict}, col::Int, rownumber::Int, ::Type{T}) where {strict, T}
rownumber == q.current_rownumber[] || wrongrow(rownumber)
handle = _get_stmt_handle(q.stmt)
t = C.sqlite3_column_type(handle, col - 1)
if t == C.SQLITE_NULL
return missing
elseif strict
return sqlitevalue(T, handle, col)
else
TT = juliatype(t) # native SQLite Int, Float, and Text types
return sqlitevalue(
Expand Down Expand Up @@ -133,11 +135,14 @@ Calling `SQLite.reset!(result)` will re-execute the query and reset the iterator

The resultset iterator supports the [Tables.jl](https://github.com/JuliaData/Tables.jl) interface, so results can be collected in any Tables.jl-compatible sink,
like `DataFrame(results)`, `CSV.write("results.csv", results)`, etc.

Passing `strict=true` to `DBInterface.execute` will cause the resultset iterator to return values of the exact type specified by SQLite.
"""
function DBInterface.execute(
stmt::Stmt,
params::DBInterface.StatementParams;
allowduplicates::Bool = false,
strict::Bool = false,
)
status = execute(stmt, params)
handle = _get_stmt_handle(stmt)
Expand All @@ -158,7 +163,7 @@ function DBInterface.execute(
header[i] = nm
types[i] = Union{juliatype(handle, i),Missing}
end
return Query(
return Query{strict}(
stmt,
Ref(status),
header,
Expand Down