thunderstrike/purescript-postgresql-client
thunderstrike/purescript-postgresql-client
2
0
Fork 0
generated from tpl/purs
Code Issues Pull Requests Packages Projects Releases Wiki Activity

README: Add withTransaction to the docs.

Browse Source
This commit is contained in:
Tomasz Rybarczyk 2018-10-21 11:50:20 +02:00
parent f7f2e3c960
commit 1d75dd5644
1 changed files with 28 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
README.md
View File

@ -18,7 +18,7 @@ module Test.Example where
import Prelude
import Database.PostgreSQL (defaultPoolConfiguration, command, execute, newPool, query, Query(Query), withConnection)
import Database.PostgreSQL (defaultPoolConfiguration, command, execute, newPool, query, Query(Query), withConnection, withTransaction)
import Database.PostgreSQL.Row (Row0(Row0), Row3(Row3))
import Data.Decimal as Decimal
import Data.Maybe (Maybe(..))
@ -63,7 +63,16 @@ The last `Row0` value indicates that this `Query` doesn't take any additional pa
""") Row0
```
We can insert some data calling `execute` function with `INSERT` statement.
There is `withTransaction` helper provided. You can wrap the whole
interaction with database in it. It will rollback if any exception
is thrown during execution of given `Aff` block. It commits in the other case.
```purescript
withTransaction conn $ do
```
Now we can insert some data calling `execute` function with `INSERT` statement.
Please notice that we are passing a tuple of arguments to this query
using dedicated constructor. In this case `Row3`.
This library provides types from `Row0` to `Row19` and they are wrappers which
@ -71,10 +80,10 @@ provides instances for automatic conversions from and to SQL values. For details
you can check classes like `ToSQLRow`, `ToSQLValue`, `FromSQLRow` and `FromSQLValue`.
```purescript
execute conn (Query """
INSERT INTO fruits (name, delicious, price)
VALUES ($1, $2, $3)
""") (Row3 "coconut" true (Decimal.fromString "8.30"))
execute conn (Query """
INSERT INTO fruits (name, delicious, price)
VALUES ($1, $2, $3)
""") (Row3 "coconut" true (Decimal.fromString "8.30"))
```
@ -83,11 +92,10 @@ verbose but is not restricted to limited and constant number of arguments.
`/\` is just an alias for the `Tuple` constructor from `Data.Tuple.Nested`.
```purescript
execute conn (Query """
INSERT INTO fruits (name, delicious, price)
VALUES ($1, $2, $3)
""") ("lemon" /\ false /\ Decimal.fromString "3.30")
execute conn (Query """
INSERT INTO fruits (name, delicious, price)
VALUES ($1, $2, $3)
""") ("lemon" /\ false /\ Decimal.fromString "3.30")
```
Of course `Row*` types and nested tuples can be also used when we are fetching
@ -96,24 +104,23 @@ data from db.
```purescript
names <- query conn (Query """
SELECT name, delicious
FROM fruits
ORDER BY name ASC
""") Row0
liftEffect <<< assert $ names == ["coconut" /\ true, "lemon" /\ false]
names <- query conn (Query """
SELECT name, delicious
FROM fruits
ORDER BY name ASC
""") Row0
liftEffect <<< assert $ names == ["coconut" /\ true, "lemon" /\ false]
```
There is also a `command` function at our disposal.
Some postgres SQL expressions return a "command tag" which carries
a value of rows which were affected by a given query.
a value with a number of rows which were affected by a given query.
For example we can have: `DELETE rows`, `UPDATE rows`, `INSERT oid rows` etc.
This function should return `rows` value associated with given response.
```purescript
deleted <- command conn (Query """DELETE FROM fruits """) Row0
liftEffect <<< assert $ deleted == 2
deleted <- command conn (Query """DELETE FROM fruits """) Row0
liftEffect <<< assert $ deleted == 2
```
## Testing