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DBinterface.jl Support #271

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DBinterface.jl Support #271

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6b25452
DBInterface integration
chris-b1 Mar 23, 2023
a0cd896
remove module prefix
chris-b1 Mar 23, 2023
8d6a987
fmt
chris-b1 Mar 23, 2023
4f746fb
fmt again
chris-b1 Mar 23, 2023
3429f49
add test for DBInterface.prepare
chris-b1 Mar 28, 2023
7f380dd
Update test/runtests.jl
chris-b1 Mar 28, 2023
81e68da
Update test/runtests.jl
chris-b1 Mar 29, 2023
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1 change: 1 addition & 0 deletions .gitignore
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@@ -1,4 +1,5 @@
.DS_Store
.vscode
*.jl.cov
*.jl.*.cov
*.jl.mem
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2 changes: 2 additions & 0 deletions Project.toml
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Expand Up @@ -5,6 +5,7 @@ version = "1.15.1"

[deps]
CEnum = "fa961155-64e5-5f13-b03f-caf6b980ea82"
DBInterface = "a10d1c49-ce27-4219-8d33-6db1a4562965"
Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
Decimals = "abce61dc-4473-55a0-ba07-351d65e31d42"
DocStringExtensions = "ffbed154-4ef7-542d-bbb7-c09d3a79fcae"
Expand All @@ -25,6 +26,7 @@ UTCDateTimes = "0f7cfa37-7abf-4834-b969-a8aa512401c2"
[compat]
CEnum = "0.2, 0.3, 0.4"
DataFrames = "0.20, 0.21, 0.22, 1"
DBInterface = "2"
Decimals = "0.4.1"
DocStringExtensions = "0.8.0, 0.9.1"
Infinity = "0.2"
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13 changes: 13 additions & 0 deletions docs/src/index.md
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Expand Up @@ -99,3 +99,16 @@ execute(conn, copyin)

close(conn)
```

### `DBInterface Integration`

LibPQ types can also be used with the generic [DBInterface.jl](https://github.com/JuliaDatabases/DBInterface.jl)
package to connect to and query Postgres databases.

```julia
using LibPQ, DBInterface

conn = DBInterface.connect(LibPQ.Connection, "dbname=postgres")
res = DBInterface.execute(con, "SELECT * FROM table")
DBInterface.close!(conn)
```
2 changes: 2 additions & 0 deletions src/LibPQ.jl
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Expand Up @@ -29,6 +29,7 @@ using OffsetArrays
using SQLStrings
using TimeZones
using UTCDateTimes
using DBInterface

const Parameter = Union{String,Missing}
const LOGGER = getlogger(@__MODULE__)
Expand Down Expand Up @@ -95,6 +96,7 @@ include("exceptions.jl")
include("parsing.jl")
include("copy.jl")
include("tables.jl")
include("dbinterface.jl")

include("asyncresults.jl")

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9 changes: 9 additions & 0 deletions src/dbinterface.jl
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@@ -0,0 +1,9 @@
DBInterface.connect(::Type{Connection}, args...; kws...) = Connection(args...; kws...)

DBInterface.prepare(conn::Connection, args...; kws...) = prepare(conn, args...; kws...)
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Is there a reason why this function needs to have separate, identically named bindings with identical method signatures in DBInterface and LibPQ? If a dependency on DBInterface is added anyway, it seems like the current definition of prepare could just extend then reexport the binding from DBInterface. Same for execute.

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LibPQ.jl is not currently fully compliant with the interface. The solution presented here avoids bringing it into compliance in favour of providing partial compliance. The future solution to bring it into compliance is either to augment LibPQ.jl's interface to bring it to compliance, or to wrap that interface with a compliant one, and this strategy allows both options.

An example of partial compliance: prepare does not have a do-block form. In LibPQ.jl, I think it would make the most sense if that form actually used the function to operate on the statement and then deallocate the statement at the end, rather than the DBInterface method which says the function should be f()::DBInterface.Connection (I don't see why that would be particularly useful). Having separate dispatches for these two functions allows both to be implemented in the future.


function DBInterface.execute(conn::Union{Connection,Statement}, args...; kws...)
return execute(conn, args...; kws...)
end

DBInterface.close!(conn::Connection) = close(conn)
39 changes: 39 additions & 0 deletions test/runtests.jl
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Expand Up @@ -11,6 +11,7 @@ using Memento
using Memento.TestUtils
using OffsetArrays
using SQLStrings
using DBInterface
using TimeZones
using Tables
using UTCDateTimes
Expand Down Expand Up @@ -1893,6 +1894,44 @@ end

close(conn)
end

@testset "DBInterface integration" begin
conn = DBInterface.connect(LibPQ.Connection, "dbname=postgres user=$DATABASE_USER")
@test conn isa LibPQ.Connection

result = DBInterface.execute(
conn,
"SELECT typname FROM pg_type WHERE oid = 16";
)
@test result isa LibPQ.Result
@test status(result) == LibPQ.libpq_c.PGRES_TUPLES_OK
@test isopen(result)
@test LibPQ.num_columns(result) == 1
@test LibPQ.num_rows(result) == 1
@test LibPQ.column_name(result, 1) == "typname"
@test LibPQ.column_number(result, "typname") == 1
data = columntable(result)
@test data[:typname][1] == "bool"

qstr = "SELECT \$1::double precision as foo, typname FROM pg_type WHERE oid = \$2"
stmt = DBInterface.prepare(conn, qstr)
result = DBInterface.execute(
conn,
qstr,
(1.0, 16);
)
@test result isa LibPQ.Result
@test status(result) == LibPQ.libpq_c.PGRES_TUPLES_OK
@test isopen(result)
@test LibPQ.num_columns(result) == 2
@test LibPQ.num_rows(result) == 1
@test LibPQ.column_name(result, 1) == "foo"
@test LibPQ.column_name(result, 2) == "typname"

DBInterface.close!(result)
@test !isopen(result)
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end
end
end

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