basic-cli/examples/sqlite-everything.roc at main · roc-lang/basic-cli · GitHub

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## Shows SQLite queries, decoders, nullable values, and prepared writes.

app [main!] { pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.23.0-rc1/3hT3SoHZ6qbEsa9qVFLUW3547U5LeoNd1KbpqLpz4r1i.tar.zst" }

import pf.OsStr

import pf.Env

import pf.Stdout

import pf.Sqlite

import pf.Path

# Sql that was used to create the table:

# CREATE TABLE todos (

# id INTEGER PRIMARY KEY AUTOINCREMENT,

# task TEXT NOT NULL,

# status TEXT NOT NULL,

# edited BOOLEAN,

# );

# Note 1: the edited column is nullable, this is for demonstration purposes only.

# We recommend using `NOT NULL` when possible.

# Note 2: boolean is "fake" in sqlite https://www.sqlite.org/datatype3.html

main! : List(OsStr) => Try({}, _)

main! = |_args| run!()

run! : () => Try({}, _)

run! = || {

# Read from environment variable, or use default

db_path = match Env.var!("DB_PATH") {

Ok(p) => Path.from_os_str(p)

Err(_) => "./examples/todos2.db"

}

# Example: print all rows

all_todos = Sqlite.query_many!({

path: db_path,

query: "SELECT * FROM todos;",

bindings: [],

rows: decode_full_todo,

}) ? |err| QueryAllTodosFailed(err)

print_line!("All Todos:")?

for t in all_todos {

print_line!(" id: ${I64.to_str(t.id)}, task: ${t.task}, status: ${status_to_str(t.status)}, edited: ${edited_to_str(decode_edited(t.edited_val))}")?

}

# Keep a runtime-allocated string live after binding it. This guards against

# the host recursively releasing fields that remain owned by the Roc caller.

heap_binding = Str.repeat("x", 40)

Sqlite.execute!({

path: db_path,

query: "UPDATE todos SET task = task WHERE task = :never;",

bindings: [{ name: ":never", value: String(heap_binding) }],

}) ? |err| HeapStringBindingFailed(err)

expect heap_binding == "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

# Example: filter rows by status (decode a single column)

tasks_in_progress = Sqlite.query_many!({

path: db_path,

query: "SELECT id, task, status FROM todos WHERE status = :status;",

bindings: [{ name: ":status", value: encode_status(InProgress) }],

rows: Sqlite.str("task"),

}) ? |err| QueryInProgressTasksFailed(err)

print_line!("")?

print_line!("In-progress Todos:")?

for task in tasks_in_progress {

print_line!(" In-progress task: ${task}")?

}

# Example: insert a row

Sqlite.execute!({

path: db_path,

query: "INSERT INTO todos (task, status, edited) VALUES (:task, :status, :edited);",

bindings: [

{ name: ":task", value: String("Make sql example.") },

{ name: ":status", value: encode_status(InProgress) },

{ name: ":edited", value: encode_edited(NotEdited) },

}) ? |err| InsertTodoFailed(err)

# Example: insert multiple rows from a Roc list

todos_list = [

{ task: "Insert Roc list 1", status: Todo, edited: NotEdited },

{ task: "Insert Roc list 2", status: Todo, edited: NotEdited },

{ task: "Insert Roc list 3", status: Todo, edited: NotEdited },

]

values_str = Str.join_with(

todos_list.map_with_index(

|_t, indx| {

i = U64.to_str(indx)

"(:task${i}, :status${i}, :edited${i})"

", ",

)

# Bindings map each named placeholder (like :task0) in the query to its actual

# value. Passing values this way lets SQLite handle escaping and type conversion,

# which avoids SQL injection and quoting bugs from building the query as a string.

binding_groups = List.map_with_index(

todos_list,

|t, indx| {

i = U64.to_str(indx)

[

{ name: ":task${i}", value: String(t.task) },

{ name: ":status${i}", value: encode_status(t.status) },

{ name: ":edited${i}", value: encode_edited(t.edited) },

]

)

all_bindings = Iter.fold(List.iter(binding_groups), [], |acc, group| List.concat(acc, group))

Sqlite.execute!({

path: db_path,

query: "INSERT INTO todos (task, status, edited) VALUES ${values_str};",

bindings: all_bindings,

}) ? |err| InsertTodoListFailed(err)

# Example: update a row

Sqlite.execute!({

path: db_path,

query: "UPDATE todos SET status = :status WHERE task = :task;",

bindings: [

{ name: ":task", value: String("Make sql example.") },

{ name: ":status", value: encode_status(Completed) },

}) ? |err| UpdateTodoFailed(err)

# Example: delete a row

Sqlite.execute!({

path: db_path,

query: "DELETE FROM todos WHERE task = :task;",

bindings: [{ name: ":task", value: String("Make sql example.") }],

}) ? |err| DeleteTodoFailed(err)

# Example: delete all rows where ID is greater than 3 (cleanup so this example is repeatable)

Sqlite.execute!({

path: db_path,

query: "DELETE FROM todos WHERE id > :id;",

bindings: [{ name: ":id", value: Integer(3) }],

}) ? |err| CleanupInsertedTodosFailed(err)

# Example: count the number of rows

count = Sqlite.query!({

path: db_path,

query: "SELECT COUNT(*) as \"count\" FROM todos;",

bindings: [],

row: Sqlite.u64("count"),

}) ? |err| CountTodosFailed(err)

print_line!("")?

print_line!("Row count: ${U64.to_str(count)}")?

# Example: prepared statements

# Note: This is faster if you execute the same prepared statement many times.

prepared_update = Sqlite.prepare!({

path: db_path,

query: "UPDATE todos SET status = status WHERE id = :id;",

}) ? |err| PrepareUpdateTodoFailed(err)

prepared_update.execute!([{ name: ":id", value: Integer(1) }]) ? |err| ExecutePreparedUpdateFailed(err)

# You can run the same prepared statement again with different values.

# Each execution starts fresh, so the previous run's values don't carry over.

prepared_update.execute!([{ name: ":id", value: Integer(2) }]) ? |err| ReusePreparedUpdateFailed(err)

prepared_count = Sqlite.prepare!({

path: db_path,

query: "SELECT COUNT(*) as \"count\" FROM todos;",

}) ? |err| PrepareCountTodosFailed(err)

prepared_count_value = prepared_count.query!([], Sqlite.u64("count")) ? |err| QueryPreparedCountFailed(err)

expect prepared_count_value == count

prepared_query = Sqlite.prepare!({

path: db_path,

# sort by the length of the task description

query: "SELECT * FROM todos ORDER BY LENGTH(task);",

}) ? |err| PrepareSortedTodosFailed(err)

todos_sorted = prepared_query.query_many!([], decode_task_status) ? |err| QuerySortedTodosFailed(err)

# Note that the result is not cached if we run the same prepared query again.

todos_sorted_again = prepared_query.query_many!([], decode_task_status) ? |err| ReuseSortedTodosFailed(err)

expect todos_sorted_again.len() == todos_sorted.len()

print_line!("")?

print_line!("Todos sorted by length of task description:")?

for t in todos_sorted {

print_line!(" task: ${t.task}, status: ${status_to_str(t.status)}")?

}

Ok({})

}

print_line! : Str => Try({}, _)

print_line! = |s| Stdout.line!(s)

# Decode every column of the todos table. The nullable `edited` column is returned

# raw (`[NotNull(I64), Null]`) and interpreted by `decode_edited` at the call site:

# decoding both `status` (via `?`) and `edited` inside this nested decoder lambda

# currently panics the type checker, so we keep only one interpreting `?` here.

decode_full_todo = |cols|

|stmt| {

id = Sqlite.i64("id")(cols)(stmt)?

task = Sqlite.str("task")(cols)(stmt)?

status_str = Sqlite.str("status")(cols)(stmt)?

match decode_status(status_str) {

Ok(status) => {

edited_val = Sqlite.nullable_i64("edited")(cols)(stmt)?

Ok({ id, task, status, edited_val })

}

Err(ParseError(message)) => Err(ParseError(message))

}

# Decode just the task and status columns.

decode_task_status = |cols|

|stmt| {

task = Sqlite.str("task")(cols)(stmt)?

status_str = Sqlite.str("status")(cols)(stmt)?

match decode_status(status_str) {

Ok(status) => Ok({ task, status })

Err(ParseError(message)) => Err(ParseError(message))

}

TodoStatus : [Todo, Completed, InProgress]

decode_status = |status_str|

match status_str {

"todo" => Ok(Todo)

"completed" => Ok(Completed)

"in-progress" => Ok(InProgress)

_ => Err(ParseError("Unknown status str: ${status_str}"))

}

status_to_str : TodoStatus -> Str

status_to_str = |status|

match status {

Todo => "todo"

Completed => "completed"

InProgress => "in-progress"

}

encode_status = |status| String(status_to_str(status))

EditedValue : [Edited, NotEdited, Unknown]

decode_edited = |edited_val|

match edited_val {

NotNull(1) => Edited

NotNull(0) => NotEdited

_ => Unknown

}

edited_to_str : EditedValue -> Str

edited_to_str = |edited|

match edited {

Edited => "edited"

NotEdited => "not-edited"

Unknown => "unknown"

}

encode_edited = |edited|

match edited {

Edited => Integer(1)

NotEdited => Integer(0)

Unknown => Null

}

basic-cli/examples/sqlite-everything.roc at main · roc-lang/basic-cli · GitHub

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