redb

https://docs.rs/redb/4.1.0/redb/
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redb is a simple, portable, high-performance, ACID-compliant, embedded key-value store written in...
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### pub fn get<'a>(&self, key: impl Borrow<K::SelfType<'a>>) -> Result<Option<AccessGuard<'static, V>>>

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyTable.html

Retrieves the value associated with the given key. The returned AccessGuard is reference counted and keeps the transaction alive until dropped.

```APIDOC
## pub fn get<'a>(&self, key: impl Borrow<K::SelfType<'a>>) -> Result<Option<AccessGuard<'static, V>>>

### Description
Retrieves the value associated with the given key. The returned AccessGuard is reference counted and keeps the transaction alive until dropped.
```

--------------------------------

### get

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

Retrieves the value corresponding to the given key from the table.

```APIDOC
## fn get<'a>( &self, key: impl Borrow<K::SelfType<'a>>, ) -> Result<Option<AccessGuard<'_, V>>>

### Description
Returns the value corresponding to the given key.
```

--------------------------------

### MutInPlaceValue Implementation for &[u8]

Source: https://docs.rs/redb/4.1.0/redb/trait.MutInPlaceValue.html

Example implementation of MutInPlaceValue for the byte slice type.

```rust
impl MutInPlaceValue for &[u8]

type BaseRefType = [u8]

fn initialize(_data: &mut [u8])

fn from_bytes_mut(data: &mut [u8]) -> &mut Self::BaseRefType
```

--------------------------------

### get

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyMultimapTable.html

Retrieves an iterator over all values for the given key. The returned iterator is reference counted and keeps the transaction alive until it is dropped.

```APIDOC
pub fn get<'a>(&self, key: impl Borrow<K::SelfType<'a>>) -> Result<MultimapValue<'static, V>>
```

--------------------------------

### Basic database usage

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

Demonstrates creating a database, opening a table, inserting data, and committing a write transaction.

```rust
use redb::*;
const TABLE: TableDefinition<u64, u64> = TableDefinition::new("my_data");

let db = Database::create(filename)?;
let write_txn = db.begin_write()?;
{
    let mut table = write_txn.open_table(TABLE)?;
    table.insert(&0, &0)?;
}
write_txn.commit()?;
```

--------------------------------

### Perform Basic Database Operations

Source: https://docs.rs/redb/4.1.0/redb/index.html

Demonstrates creating a database, performing a write transaction to insert data, and executing a read transaction to retrieve it.

```rust
use redb::{Database, Error, ReadableDatabase, ReadableTable, TableDefinition};

const TABLE: TableDefinition<&str, u64> = TableDefinition::new("my_data");

fn main() -> Result<(), Error> {
    let file = tempfile::NamedTempFile::new().unwrap();
    let db = Database::create(file.path())?;
    let write_txn = db.begin_write()?;
    {
        let mut table = write_txn.open_table(TABLE)?;
        table.insert("my_key", &123)?;
    }
    write_txn.commit()?;

    let read_txn = db.begin_read()?;
    let table = read_txn.open_table(TABLE)?;
    assert_eq!(table.get("my_key")?.unwrap().value(), 123);

    Ok(())
}
```

--------------------------------

### Builder::create

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Initializes or opens a database at the specified path.

```APIDOC
## pub fn create(&self, path: impl AsRef<Path>) -> Result<Database, DatabaseError>

### Description
Opens the specified file as a redb database. If the file does not exist or is empty, a new database is initialized.
```

--------------------------------

### Database::create

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

Opens the specified file as a redb database. If the file does not exist or is empty, a new database is initialized.

```APIDOC
## Database::create

### Description
Opens the specified file as a redb database. If the file does not exist, or is an empty file, a new database will be initialized in it. If the file is a valid redb database, it will be opened.

### Signature
`pub fn create(path: impl AsRef<Path>) -> Result<Database, DatabaseError>`
```

--------------------------------

### Open and read from a database

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyDatabase.html

Demonstrates creating a database, writing data, and then opening it in read-only mode to perform a read transaction.

```rust
use redb::*;
const TABLE: TableDefinition<u64, u64> = TableDefinition::new("my_data");

let db = Database::create(filename)?;
let txn = db.begin_write()?;
{
    let mut table = txn.open_table(TABLE)?;
    table.insert(&0, &0)?;
}
txn.commit()?;
drop(db);

let db = ReadOnlyDatabase::open(filename)?;
let txn = db.begin_read()?;
{
    let mut table = txn.open_table(TABLE)?;
    println!("{}", table.get(&0)?.unwrap().value());
}
```

--------------------------------

### Builder::create_with_backend

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Opens or creates a database using a custom storage backend.

```APIDOC
## pub fn create_with_backend(&self, backend: impl StorageBackend) -> Result<Database, DatabaseError>

### Description
Open an existing or create a new database with the given backend.
```

--------------------------------

### Builder::open

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Opens an existing redb database.

```APIDOC
## pub fn open(&self, path: impl AsRef<Path>) -> Result<Database, DatabaseError>

### Description
Opens an existing redb database.
```

--------------------------------

### Builder::create_file

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Opens or creates a database using a provided File handle.

```APIDOC
## pub fn create_file(&self, file: File) -> Result<Database, DatabaseError>

### Description
Open an existing or create a new database in the given file. The file must be empty or contain a valid database.
```

--------------------------------

### FileBackend::new

Source: https://docs.rs/redb/4.1.0/redb/backends/struct.FileBackend.html

Creates a new FileBackend instance that stores data to the provided file.

```APIDOC
## pub fn new(file: File) -> Result<Self, DatabaseError>

### Description
Creates a new backend which stores data to the given file.

### Parameters
- **file** (File) - Required - The file handle to be used for storage.
```

--------------------------------

### Product implementation for Result

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Demonstrates using the product method on an iterator of Results, which short-circuits on the first Err encountered.

```rust
let nums = vec!["5", "10", "1", "2"];
let total: Result<usize, _> = nums.iter().map(|w| w.parse::<usize>()).product();
assert_eq!(total, Ok(100));
let nums = vec!["5", "10", "one", "2"];
let total: Result<usize, _> = nums.iter().map(|w| w.parse::<usize>()).product();
assert!(total.is_err());
```

--------------------------------

### Database::open

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

Opens an existing redb database from the specified path.

```APIDOC
## Database::open

### Description
Opens an existing redb database.

### Signature
`pub fn open(path: impl AsRef<Path>) -> Result<Database, DatabaseError>`
```

--------------------------------

### begin_read

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

Begins a read transaction on the database.

```APIDOC
### fn begin_read(&self) -> Result<ReadTransaction, TransactionError>

Begins a read transaction for the database instance.
```

--------------------------------

### open_table

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Opens a table, creating it if it does not exist.

```APIDOC
## pub fn open_table<'txn, K: Key + 'static, V: Value + 'static>( &'txn self, definition: TableDefinition<'_, K, V>, ) -> Result<Table<'txn, K, V>, TableError>

### Description
Opens the specified table. If the table does not exist, it will be created.
```

--------------------------------

### Builder::new

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Constructs a new Builder instance with default settings (cache_size_bytes: 1GiB).

```APIDOC
## pub fn new() -> Self

### Description
Construct a new Builder with sensible defaults.

### Defaults
- cache_size_bytes: 1GiB
```

--------------------------------

### Constructing a MultimapTableDefinition

Source: https://docs.rs/redb/4.1.0/redb/struct.MultimapTableDefinition.html

Creates a new definition instance. Panics if the provided name is empty.

```rust
pub const fn new(name: &'a str) -> Self
```

--------------------------------

### Database::begin_write

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

Begins a write transaction, allowing read and write operations on the database.

```APIDOC
## Database::begin_write

### Description
Begins a write transaction. Returns a WriteTransaction which may be used to read/write to the database. Only a single write may be in progress at a time; this function will block if another write is in progress.

### Signature
`pub fn begin_write(&self) -> Result<WriteTransaction, TransactionError>`
```

--------------------------------

### TableDefinition::new

Source: https://docs.rs/redb/4.1.0/redb/struct.TableDefinition.html

Constructs a new TableDefinition with the specified name. Panics if the name is empty.

```APIDOC
## pub const fn new(name: &'a str) -> Self

### Description
Constructs a new table definition with the given name. This is used to identify the table when opening it via a transaction.

### Parameters
- **name** (&str) - Required - The name of the table. Must not be empty.

### Panics
Panics if the provided name is empty.
```

--------------------------------

### open_multimap_table

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Opens a multimap table, creating it if it does not exist.

```APIDOC
## pub fn open_multimap_table<'txn, K: Key + 'static, V: Key + 'static>( &'txn self, definition: MultimapTableDefinition<'_, K, V>, ) -> Result<MultimapTable<'txn, K, V>, TableError>

### Description
Opens the specified multimap table. If the table does not exist, it will be created.
```

--------------------------------

### Builder::open_read_only

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Opens an existing redb database in read-only mode.

```APIDOC
## pub fn open_read_only(&self, path: impl AsRef<Path>) -> Result<ReadOnlyDatabase, DatabaseError>

### Description
Opens an existing redb database in read-only mode. Returns DatabaseError::DatabaseAlreadyOpen if the file is already opened for writing on supported platforms.
```

--------------------------------

### set_quick_repair

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Enable or disable quick-repair mode for the database.

```APIDOC
## pub fn set_quick_repair(&mut self, enabled: bool)

### Description
Enable or disable quick-repair. By default, this is disabled. When enabled, redb saves the allocator state during commits and uses 2-phase commit, making crash recovery almost instant at the cost of slower commits.
```

--------------------------------

### TypeName::new

Source: https://docs.rs/redb/4.1.0/redb/struct.TypeName.html

Creates a new instance of TypeName with the specified name.

```APIDOC
## pub fn new(name: &str) -> Self

### Description
Creates a new TypeName instance. It is recommended that the provided name be prefixed with the crate name to minimize the chance of colliding with other user-defined types.

### Parameters
- **name** (&str) - Required - The name to assign to the TypeName instance.
```

--------------------------------

### stats()

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyUntypedMultimapTable.html

Retrieves information about storage usage for the table.

```APIDOC
## fn stats(&self) -> Result<TableStats>

### Description
Retrieves information about storage usage for the table.
```

--------------------------------

### first

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

Retrieves the first key-value pair in the table.

```APIDOC
## fn first(&self) -> Result<Option<(AccessGuard<'_, K>, AccessGuard<'_, V>)>>

### Description
Returns the first key-value pair in the table, if it exists.
```

--------------------------------

### Into Ok

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Extracts the Ok value without risk of panicking, intended for infallible results.

```rust
fn only_good_news() -> Result<String, !> {
    Ok("this is fine".into())
}

let s: String = only_good_news().into_ok();
println!("{s}");
```

--------------------------------

### expect

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the contained Ok value, consuming the self value, or panics if Err.

```APIDOC
## pub fn expect(self, msg: &str) -> T

### Description
Returns the contained `Ok` value, consuming the `self` value. Panics if the value is an `Err`, with a panic message including the passed message, and the content of the `Err`.
```

--------------------------------

### list_tables

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Lists all tables in the database.

```APIDOC
## pub fn list_tables( &self, ) -> Result<impl Iterator<Item = UntypedTableHandle> + '_>

### Description
Returns an iterator over all tables currently in the database.
```

--------------------------------

### MultimapTableDefinition::new

Source: https://docs.rs/redb/4.1.0/redb/struct.MultimapTableDefinition.html

Constructs a new MultimapTableDefinition with the specified name. Panics if the provided name is empty.

```APIDOC
## pub const fn new(name: &'a str) -> Self

### Description
Constructs a new multimap table definition with the given name.

### Parameters
- **name** (&str) - Required - The name of the multimap table. Must be non-empty.

### Panics
Panics if the provided `name` is empty.
```

--------------------------------

### Perform Range Query on Table

Source: https://docs.rs/redb/4.1.0/redb/trait.ReadableTable.html

Demonstrates using the range method to iterate over a subset of table entries.

```rust
use redb::*;
const TABLE: TableDefinition<&str, u64> = TableDefinition::new("my_data");

let db = Database::create(filename)?;
let write_txn = db.begin_write()?;
{
    let mut table = write_txn.open_table(TABLE)?;
    table.insert("a", &0)?;
    table.insert("b", &1)?;
    table.insert("c", &2)?;
}
write_txn.commit()?;

let read_txn = db.begin_read()?;
let table = read_txn.open_table(TABLE)?;
let mut iter = table.range("a".."c")?;
let (key, value) = iter.next().unwrap()?;
assert_eq!("a", key.value());
assert_eq!(0, value.value());
```

--------------------------------

### ReadOnlyDatabase::begin_read

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyDatabase.html

Begins a read transaction on the database.

```APIDOC
## fn begin_read(&self) -> Result<ReadTransaction, TransactionError>

### Description
Begins a read transaction, allowing the user to perform read operations on the database.

### Returns
- **Result<ReadTransaction, TransactionError>** - Returns a ReadTransaction object on success, or a TransactionError if the transaction could not be started.
```

--------------------------------

### And Chaining

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the provided result if the current result is Ok, otherwise returns the Err.

```rust
let x: Result<u32, &str> = Ok(2);
let y: Result<&str, &str> = Err("late error");
assert_eq!(x.and(y), Err("late error"));

let x: Result<u32, &str> = Err("early error");
let y: Result<&str, &str> = Ok("foo");
assert_eq!(x.and(y), Err("early error"));

let x: Result<u32, &str> = Err("not a 2");
let y: Result<&str, &str> = Err("late error");
assert_eq!(x.and(y), Err("not a 2"));

let x: Result<u32, &str> = Ok(2);
let y: Result<&str, &str> = Ok("different result type");
assert_eq!(x.and(y), Ok("different result type"));
```

--------------------------------

### Provide fallback results with or

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the current result if it is Ok, otherwise returns the provided alternative result. Note that arguments are eagerly evaluated.

```rust
let x: Result<u32, &str> = Ok(2);
let y: Result<u32, &str> = Err("late error");
assert_eq!(x.or(y), Ok(2));

let x: Result<u32, &str> = Err("early error");
let y: Result<u32, &str> = Ok(2);
assert_eq!(x.or(y), Ok(2));

let x: Result<u32, &str> = Err("not a 2");
let y: Result<u32, &str> = Err("late error");
assert_eq!(x.or(y), Err("late error"));

let x: Result<u32, &str> = Ok(2);
let y: Result<u32, &str> = Ok(100);
assert_eq!(x.or(y), Ok(2));
```

--------------------------------

### name

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

Returns the name of the table.

```APIDOC
## fn name(&self) -> &str

### Description
Returns the name of the table.
```

--------------------------------

### stats

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Retrieves database storage statistics.

```APIDOC
## pub fn stats(&self) -> Result<DatabaseStats>

### Description
Retrieves information regarding storage usage within the database.
```

--------------------------------

### Unwrap Result or Default

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the Ok value or the default value of the type if the result is an Err.

```rust
let good_year_from_input = "1909";
let bad_year_from_input = "190blarg";
let good_year = good_year_from_input.parse().unwrap_or_default();
let bad_year = bad_year_from_input.parse().unwrap_or_default();

assert_eq!(1909, good_year);
assert_eq!(0, bad_year);
```

--------------------------------

### Database::compact

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

Compacts the database file to reclaim space.

```APIDOC
## Database::compact

### Description
Compacts the database file. Returns true if compaction was performed, and false if no further compaction was possible.

### Signature
`pub fn compact(&mut self) -> Result<bool, CompactionError>`
```

--------------------------------

### Retrieve values with unwrap_or

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the contained Ok value or a provided default value. Arguments are eagerly evaluated.

```rust
let default = 2;
let x: Result<u32, &str> = Ok(9);
assert_eq!(x.unwrap_or(default), 9);

let x: Result<u32, &str> = Err("error");
assert_eq!(x.unwrap_or(default), default);
```

--------------------------------

### StorageBackend Trait Definition

Source: https://docs.rs/redb/4.1.0/redb/trait.StorageBackend.html

The core trait definition for implementing custom storage backends in redb.

```rust
pub trait StorageBackend:
    'static
    + Debug
    + Send
    + Sync {
    // Required methods
    fn len(&self) -> Result<u64, Error>;
    fn read(&self, offset: u64, out: &mut [u8]) -> Result<(), Error>;
    fn set_len(&self, len: u64) -> Result<(), Error>;
    fn sync_data(&self) -> Result<(), Error>;
    fn write(&self, offset: u64, data: &[u8]) -> Result<(), Error>;

    // Provided method
    fn close(&self) -> Result<(), Error> { ... }
}
```

--------------------------------

### ReadOnlyDatabase::open

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyDatabase.html

Opens an existing redb database at the specified path in read-only mode.

```APIDOC
## pub fn open(path: impl AsRef<Path>) -> Result<ReadOnlyDatabase, DatabaseError>

### Description
Opens an existing redb database. This allows for read-only access to the database file.

### Parameters
- **path** (impl AsRef<Path>) - Required - The file system path to the existing redb database.

### Returns
- **Result<ReadOnlyDatabase, DatabaseError>** - Returns a ReadOnlyDatabase instance on success, or a DatabaseError if the operation fails.
```

--------------------------------

### len()

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyUntypedMultimapTable.html

Returns the number of entries in the table.

```APIDOC
## fn len(&self) -> Result<u64>

### Description
Returns the number of entries in the table.
```

--------------------------------

### list_multimap_tables

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Lists all multimap tables in the database.

```APIDOC
## pub fn list_multimap_tables( &self, ) -> Result<impl Iterator<Item = UntypedMultimapTableHandle> + '_>

### Description
Returns an iterator over all multimap tables currently in the database.
```

--------------------------------

### is_empty()

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyUntypedMultimapTable.html

Returns true if the table is empty.

```APIDOC
## fn is_empty(&self) -> Result<bool>

### Description
Returns true if the table is empty.
```

--------------------------------

### And Then Chaining

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Calls a function if the result is Ok, otherwise returns the Err.

```rust
fn sq_then_to_string(x: u32) -> Result<String, &'static str> {
    x.checked_mul(x).map(|sq| sq.to_string()).ok_or("overflowed")
}
```

--------------------------------

### Database definition

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

The internal structure of the Database type.

```rust
pub struct Database { /* private fields */ }
```

--------------------------------

### Expect Error

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the Err value or panics if the result is an Ok.

```rust
let x: Result<u32, &str> = Ok(10);
x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
```

--------------------------------

### Sum implementation for Result

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Demonstrates using the sum method on an iterator of Results, which returns an Err if any element is an Err.

```rust
let f = |&x: &i32| if x < 0 { Err("Negative element found") } else { Ok(x) };
let v = vec![1, 2];
let res: Result<i32, _> = v.iter().map(f).sum();
assert_eq!(res, Ok(3));
let v = vec![1, -2];
let res: Result<i32, _> = v.iter().map(f).sum();
assert_eq!(res, Err("Negative element found"));
```

--------------------------------

### restore_savepoint

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Restores the database state to a previously created savepoint.

```APIDOC
## pub fn restore_savepoint(&mut self, savepoint: &Savepoint) -> Result<(), SavepointError>

### Description
Restore the state of the database to the given `Savepoint`. Calling this method invalidates all `Savepoint`s created after the provided savepoint.
```

--------------------------------

### Expect Result Value

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the Ok value or panics with a provided message if the result is Err.

```rust
let x: Result<u32, &str> = Err("emergency failure");
x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
```

```rust
let path = std::env::var("IMPORTANT_PATH")
    .expect("env variable `IMPORTANT_PATH` should be set by `wrapper_script.sh`");
```

--------------------------------

### Retrieve values with unwrap_or_else

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the contained Ok value or computes a default value using a closure.

```rust
fn count(x: &str) -> usize { x.len() }
```

--------------------------------

### Builder::set_cache_size

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Configures the memory cache size for the database.

```APIDOC
## pub fn set_cache_size(&mut self, bytes: usize) -> &mut Self

### Description
Set the amount of memory (in bytes) used for caching data.
```

--------------------------------

### Reference Result with as_ref and as_mut

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Converts a Result to a Result containing references to the original values.

```rust
let x: Result<u32, &str> = Ok(2);
assert_eq!(x.as_ref(), Ok(&2));

let x: Result<u32, &str> = Err("Error");
assert_eq!(x.as_ref(), Err(&"Error"));
```

```rust
fn mutate(r: &mut Result<i32, i32>) {
    match r.as_mut() {
        Ok(v) => *v = 42,
        Err(e) => *e = 0,
    }
}

let mut x: Result<i32, i32> = Ok(2);
mutate(&mut x);
assert_eq!(x.unwrap(), 42);

let mut x: Result<i32, i32> = Err(13);
mutate(&mut x);
assert_eq!(x.unwrap_err(), 0);
```

--------------------------------

### persistent_savepoint

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Creates a snapshot of the current database state that can be used to rollback the database. This savepoint persists until explicitly deleted.

```APIDOC
## pub fn persistent_savepoint(&self) -> Result<u64, SavepointError>

### Description
Creates a snapshot of the current database state, which can be used to rollback the database. This savepoint will exist until it is deleted with `delete_savepoint()`.

### Returns
- `Result<u64, SavepointError>`: Returns the ID of the created savepoint, or an error if the transaction is dirty or immediate durability is required.
```

--------------------------------

### Unwrap Error

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns the Err value or panics if the result is an Ok.

```rust
let x: Result<u32, &str> = Ok(2);
x.unwrap_err(); // panics with `2`
```

```rust
let x: Result<u32, &str> = Err("emergency failure");
assert_eq!(x.unwrap_err(), "emergency failure");
```

--------------------------------

### Inspect Ok Value

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Executes a closure with a reference to the Ok value without consuming the result.

```rust
let x: u8 = "4"
    .parse::<u8>()
    .inspect(|x| println!("original: {x}"))
    .map(|x| x.pow(3))
    .expect("failed to parse number");
```

--------------------------------

### AccessGuardMut::insert

Source: https://docs.rs/redb/4.1.0/redb/struct.AccessGuardMut.html

Replaces the currently stored value with a new one.

```APIDOC
## pub fn insert<'v>(&mut self, value: impl Borrow<V::SelfType<'v>>) -> Result<()>

### Description
Replace the stored value.

### Parameters
- **value** (impl Borrow<V::SelfType<'v>>) - The new value to store.

### Returns
- **Result<()>** - Returns Ok(()) on success, or an error if the operation fails.
```

--------------------------------

### RepairSession Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.RepairSession.html

The definition of the RepairSession struct.

```rust
pub struct RepairSession { /* private fields */ }
```

--------------------------------

### ephemeral_savepoint

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Creates a snapshot of the current database state that is automatically freed when the returned Savepoint object is dropped.

```APIDOC
## pub fn ephemeral_savepoint(&self) -> Result<Savepoint, SavepointError>

### Description
Creates a snapshot of the current database state, which can be used to rollback the database. This savepoint will be freed as soon as the returned `Savepoint` is dropped.

### Returns
- `Result<Savepoint, SavepointError>`: Returns the savepoint object, or an error if the transaction is dirty.
```

--------------------------------

### Copy Result Contents

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Copies the contents of an Ok variant for types that implement Copy.

```rust
let val = 12;
let x: Result<&i32, i32> = Ok(&val);
assert_eq!(x, Ok(&12));
let copied = x.copied();
assert_eq!(copied, Ok(12));
```

```rust
let mut val = 12;
let x: Result<&mut i32, i32> = Ok(&mut val);
assert_eq!(x, Ok(&mut 12));
let copied = x.copied();
assert_eq!(copied, Ok(12));
```

--------------------------------

### inspect

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Calls a function with a reference to the contained value if Ok. Returns the original result.

```APIDOC
## pub fn inspect<F>(self, f: F) -> Result<T, E>

### Description
Calls a function with a reference to the contained value if `Ok`. Returns the original result.
```

--------------------------------

### is_empty()

Source: https://docs.rs/redb/4.1.0/redb/struct.MultimapValue.html

Checks if the iterator is empty.

```APIDOC
## pub fn is_empty(&self) -> bool

### Description
Returns true if the iterator contains no elements.

### Returns
- **bool** - True if empty, false otherwise.
```

--------------------------------

### as_deref_mut

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Converts from Result<T, E> to Result<&mut <T as DerefMut>::Target, &mut E>.

```APIDOC
## pub fn as_deref_mut(&mut self) -> Result<&mut <T as DerefMut>::Target, &mut E>

### Description
Converts from `Result<T, E>` (or `&mut Result<T, E>`) to `Result<&mut <T as DerefMut>::Target, &mut E>`. Coerces the `Ok` variant of the original `Result` via `DerefMut` and returns the new `Result`.
```

--------------------------------

### Table mutation and access methods

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

Methods for modifying table contents, including insertion, removal, and conditional extraction.

```rust
pub fn get_mut<'k>( &mut self, key: impl Borrow<K::SelfType<'k>>, ) -> Result<Option<AccessGuardMut<'_, V>>>
```

```rust
pub fn pop_first( &mut self, ) -> Result<Option<(AccessGuard<'_, K>, AccessGuard<'_, V>)>>
```

```rust
pub fn pop_last( &mut self, ) -> Result<Option<(AccessGuard<'_, K>, AccessGuard<'_, V>)>>
```

```rust
pub fn extract_if<F: for<'f> FnMut(K::SelfType<'f>, V::SelfType<'f>) -> bool>( &mut self, predicate: F, ) -> Result<ExtractIf<'_, K, V, F>>
```

```rust
pub fn extract_from_if<'a, KR, F: for<'f> FnMut(K::SelfType<'f>, V::SelfType<'f>) -> bool>( &mut self, range: impl RangeBounds<KR> + 'a, predicate: F, ) -> Result<ExtractIf<'_, K, V, F>>
where KR: Borrow<K::SelfType<'a>> + 'a,
```

```rust
pub fn retain<F: for<'f> FnMut(K::SelfType<'f>, V::SelfType<'f>) -> bool>( &mut self, predicate: F, ) -> Result
```

```rust
pub fn retain_in<'a, KR, F: for<'f> FnMut(K::SelfType<'f>, V::SelfType<'f>) -> bool>( &mut self, range: impl RangeBounds<KR> + 'a, predicate: F, ) -> Result
where KR: Borrow<K::SelfType<'a>> + 'a,
```

```rust
pub fn insert<'k, 'v>( &mut self, key: impl Borrow<K::SelfType<'k>>, value: impl Borrow<V::SelfType<'v>>, ) -> Result<Option<AccessGuard<'_, V>>>
```

```rust
pub fn remove<'a>( &mut self, key: impl Borrow<K::SelfType<'a>>, ) -> Result<Option<AccessGuard<'_, V>>>
```

```rust
pub fn insert_reserve<'a>( &mut self, key: impl Borrow<K::SelfType<'a>>, value_length: usize, ) -> Result<AccessGuardMutInPlace<'_, V>>
```

--------------------------------

### ReadableDatabase Trait Definition

Source: https://docs.rs/redb/4.1.0/redb/trait.ReadableDatabase.html

The core trait definition for database readability, requiring implementation of transaction initiation and cache statistics retrieval.

```rust
pub trait ReadableDatabase {
    // Required methods
    fn begin_read(&self) -> Result<ReadTransaction, TransactionError>;
    fn cache_stats(&self) -> CacheStats;
}
```

--------------------------------

### as_deref

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Converts from Result<T, E> to Result<&<T as Deref>::Target, &E>.

```APIDOC
## pub fn as_deref(&self) -> Result<&<T as Deref>::Target, &E>

### Description
Converts from `Result<T, E>` (or `&Result<T, E>`) to `Result<&<T as Deref>::Target, &E>`. Coerces the `Ok` variant of the original `Result` via `Deref` and returns the new `Result`.
```

--------------------------------

### iter

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

Returns an iterator over all elements in the table.

```APIDOC
## fn iter(&self) -> Result<Range<'_, K, V>>

### Description
Returns a double-ended iterator over all elements in the table.
```

--------------------------------

### Map Result values

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Applies a function to the contained Ok value.

```rust
let line = "1\n2\n3\n4\n";

for num in line.lines() {
    match num.parse::<i32>().map(|i| i * 2) {
        Ok(n) => println!("{n}"),
        Err(..) => {}
    }
}
```

--------------------------------

### Unwrap Result Value

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Extracts the Ok value or panics if the result is an Err.

```rust
let x: Result<u32, &str> = Ok(2);
assert_eq!(x.unwrap(), 2);
```

```rust
let x: Result<u32, &str> = Err("emergency failure");
x.unwrap(); // panics with `emergency failure`
```

--------------------------------

### last

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

Retrieves the last key-value pair in the table.

```APIDOC
## fn last(&self) -> Result<Option<(AccessGuard<'_, K>, AccessGuard<'_, V>)>>

### Description
Returns the last key-value pair in the table, if it exists.
```

--------------------------------

### Check Result with is_err_and

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Checks if a Result is an Err and matches a specific predicate.

```rust
use std::io::{Error, ErrorKind};

let x: Result<u32, Error> = Err(Error::new(ErrorKind::NotFound, "!"));
assert_eq!(x.is_err_and(|x| x.kind() == ErrorKind::NotFound), true);

let x: Result<u32, Error> = Err(Error::new(ErrorKind::PermissionDenied, "!"));
assert_eq!(x.is_err_and(|x| x.kind() == ErrorKind::NotFound), false);

let x: Result<u32, Error> = Ok(123);
assert_eq!(x.is_err_and(|x| x.kind() == ErrorKind::NotFound), false);

let x: Result<u32, String> = Err("ownership".to_string());
assert_eq!(x.as_ref().is_err_and(|x| x.len() > 1), true);
println!("still alive {:?}", x);
```

--------------------------------

### AccessGuardMut::value

Source: https://docs.rs/redb/4.1.0/redb/struct.AccessGuardMut.html

Retrieves the currently stored value.

```APIDOC
## pub fn value(&self) -> V::SelfType<'_>

### Description
Access the stored value.

### Returns
- **V::SelfType<'_>** - The stored value.
```

--------------------------------

### AccessGuardMutInPlace Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.AccessGuardMutInPlace.html

The definition of the AccessGuardMutInPlace struct.

```rust
pub struct AccessGuardMutInPlace<'a, V: Value + 'static> { /* private fields */ }
```

--------------------------------

### Map Result to default or function result

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Maps a Result to a value using a default or a fallback function.

```rust
let x: Result<_, &str> = Ok("foo");
assert_eq!(x.map_or(42, |v| v.len()), 3);

let x: Result<&str, _> = Err("bar");
assert_eq!(x.map_or(42, |v| v.len()), 42);
```

```rust
let k = 21;

let x : Result<_, &str> = Ok("foo");
assert_eq!(x.map_or_else(|e| k * 2, |v| v.len()), 3);

let x : Result<&str, _> = Err("bar");
assert_eq!(x.map_or_else(|e| k * 2, |v| v.len()), 42);
```

```rust
let x: Result<_, &str> = Ok("foo");
let y: Result<&str, _> = Err("bar");

assert_eq!(x.map_or_default(|x| x.len()), 3);
assert_eq!(y.map_or_default(|y| y.len()), 0);
```

--------------------------------

### TypeName::name

Source: https://docs.rs/redb/4.1.0/redb/struct.TypeName.html

Retrieves the name associated with the TypeName instance.

```APIDOC
## pub fn name(&self) -> &str

### Description
Returns the name associated with this TypeName instance.
```

--------------------------------

### pub fn range<'a, KR>(&self, range: impl RangeBounds<KR>) -> Result<Range<'static, K, V>>

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyTable.html

Returns an iterator over a range of elements in the table. The iterator is reference counted and keeps the transaction alive until dropped.

```APIDOC
## pub fn range<'a, KR>(&self, range: impl RangeBounds<KR>) -> Result<Range<'static, K, V>>

### Description
Returns an iterator over a range of elements in the table. The iterator is reference counted and keeps the transaction alive until dropped.
```

--------------------------------

### Into Error

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Extracts the Err value without risk of panicking, intended for infallible results.

```rust
fn only_bad_news() -> Result<!, String> {
    Err("Oops, it failed".into())
}

let error: String = only_bad_news().into_err();
println!("{error}");
```

--------------------------------

### Transpose Result and Option

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Converts a Result of an Option into an Option of a Result.

```rust
#[derive(Debug, Eq, PartialEq)]
struct SomeErr;

let x: Result<Option<i32>, SomeErr> = Ok(Some(5));
let y: Option<Result<i32, SomeErr>> = Some(Ok(5));
assert_eq!(x.transpose(), y);
```

--------------------------------

### Builder::set_repair_callback

Source: https://docs.rs/redb/4.1.0/redb/struct.Builder.html

Sets a callback to be invoked if the database file requires repair.

```APIDOC
## pub fn set_repair_callback(&mut self, callback: impl Fn(&mut RepairSession) + 'static) -> &mut Self

### Description
Set a callback which will be invoked periodically in the event that the database file needs to be repaired. The RepairSession argument can be used to control the repair process.
```

--------------------------------

### Clone Result Contents

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Clones the contents of an Ok variant for types that implement Clone.

```rust
let val = 12;
let x: Result<&i32, i32> = Ok(&val);
assert_eq!(x, Ok(&12));
let cloned = x.cloned();
assert_eq!(cloned, Ok(12));
```

```rust
let mut val = 12;
let x: Result<&mut i32, i32> = Ok(&mut val);
assert_eq!(x, Ok(&mut 12));
let cloned = x.cloned();
assert_eq!(cloned, Ok(12));
```

--------------------------------

### MultimapTableDefinition Struct Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.MultimapTableDefinition.html

The primary structure definition for MultimapTableDefinition.

```rust
pub struct MultimapTableDefinition<'a, K: Key + 'static, V: Key + 'static> { /* private fields */ }
```

--------------------------------

### Table struct definition

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

The primary structure for interacting with key-value data in redb.

```rust
pub struct Table<'txn, K: Key + 'static, V: Value + 'static> { /* private fields */ }
```

--------------------------------

### Key Trait Definition

Source: https://docs.rs/redb/4.1.0/redb/trait.Key.html

The core trait definition requiring a compare method that returns an Ordering.

```rust
pub trait Key: Value {
    // Required method
    fn compare(data1: &[u8], data2: &[u8]) -> Ordering;
}
```

--------------------------------

### Define CacheStats struct

Source: https://docs.rs/redb/4.1.0/redb/struct.CacheStats.html

The definition of the CacheStats struct.

```rust
pub struct CacheStats { /* private fields */ }
```

--------------------------------

### Convert Result to Option

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Converts Result to Option, discarding the error or success value respectively.

```rust
let x: Result<u32, &str> = Ok(2);
assert_eq!(x.ok(), Some(2));

let x: Result<u32, &str> = Err("Nothing here");
assert_eq!(x.ok(), None);
```

```rust
let x: Result<u32, &str> = Ok(2);
assert_eq!(x.err(), None);

let x: Result<u32, &str> = Err("Nothing here");
assert_eq!(x.err(), Some("Nothing here"));
```

--------------------------------

### AccessGuard Struct Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.AccessGuard.html

The definition of the AccessGuard structure, which manages scoped access to database values.

```rust
pub struct AccessGuard<'a, V: Value + 'static> { /* private fields */ }
```

--------------------------------

### ReadTransaction Methods

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadTransaction.html

Methods available on the ReadTransaction struct for interacting with database tables.

```APIDOC
## pub fn open_table<K, V>(definition: TableDefinition<'_, K, V>) -> Result<ReadOnlyTable<K, V>, TableError>

### Description
Opens a typed table for reading.

## pub fn open_untyped_table(handle: impl TableHandle) -> Result<ReadOnlyUntypedTable, TableError>

### Description
Opens a table for reading without enforcing a specific type.

## pub fn open_multimap_table<K, V>(definition: MultimapTableDefinition<'_, K, V>) -> Result<ReadOnlyMultimapTable<K, V>, TableError>

### Description
Opens a typed multimap table for reading.

## pub fn open_untyped_multimap_table(handle: impl MultimapTableHandle) -> Result<ReadOnlyUntypedMultimapTable, TableError>

### Description
Opens a multimap table for reading without enforcing a specific type.

## pub fn list_tables() -> Result<impl Iterator<Item = UntypedTableHandle>>

### Description
Returns an iterator over all tables in the database.

## pub fn list_multimap_tables() -> Result<impl Iterator<Item = UntypedMultimapTableHandle>>

### Description
Returns an iterator over all multimap tables in the database.

## pub fn close(self) -> Result<(), TransactionError>

### Description
Closes the transaction. This is typically handled automatically when the transaction is dropped, but can be called manually to ensure no outstanding objects remain.
```

--------------------------------

### range

Source: https://docs.rs/redb/4.1.0/redb/struct.Table.html

Returns a double-ended iterator over a range of elements in the table.

```APIDOC
## fn range<'a, KR>( &self, range: impl RangeBounds<KR> + 'a, ) -> Result<Range<'_, K, V>>

### Description
Returns a double-ended iterator over a range of elements in the table.
```

--------------------------------

### abort

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Aborts the current transaction.

```APIDOC
## pub fn abort(self) -> Result

### Description
Aborts the transaction, rolling back all writes performed during the transaction.
```

--------------------------------

### TableDefinition Struct Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.TableDefinition.html

The primary structure definition for TableDefinition, requiring Key and Value trait implementations.

```rust
pub struct TableDefinition<'a, K: Key + 'static, V: Value + 'static> { /* private fields */ }
```

--------------------------------

### Check Result Status

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Methods to inspect whether a Result is Ok or Err.

```rust
let x: Result<i32, &str> = Ok(-3);
assert_eq!(x.is_ok(), true);

let x: Result<i32, &str> = Err("Some error message");
assert_eq!(x.is_ok(), false);
```

```rust
let x: Result<u32, &str> = Ok(2);
assert_eq!(x.is_ok_and(|x| x > 1), true);

let x: Result<u32, &str> = Ok(0);
assert_eq!(x.is_ok_and(|x| x > 1), false);

let x: Result<u32, &str> = Err("hey");
assert_eq!(x.is_ok_and(|x| x > 1), false);

let x: Result<String, &str> = Ok("ownership".to_string());
assert_eq!(x.as_ref().is_ok_and(|x| x.len() > 1), true);
println!("still alive {:?}", x);
```

```rust
let x: Result<i32, &str> = Ok(-3);
assert_eq!(x.is_err(), false);

let x: Result<i32, &str> = Err("Some error message");
assert_eq!(x.is_err(), true);
```

--------------------------------

### rename_table

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Renames an existing table.

```APIDOC
## pub fn rename_table( &self, definition: impl TableHandle, new_name: impl TableHandle, ) -> Result<(), TableError>

### Description
Renames the given table to the new name provided.
```

--------------------------------

### Savepoint Struct Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.Savepoint.html

The definition of the Savepoint struct.

```rust
pub struct Savepoint { /* private fields */ }
```

--------------------------------

### ReadOnlyMultimapTable methods

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyMultimapTable.html

Methods for retrieving values or ranges from a read-only multimap table.

```rust
pub fn get<'a>( &self, key: impl Borrow<K::SelfType<'a>>, ) -> Result<MultimapValue<'static, V>>
```

```rust
pub fn range<'a, KR>( &self, range: impl RangeBounds<KR>, ) -> Result<MultimapRange<'static, K, V>>
where KR: Borrow<K::SelfType<'a>>,
```

--------------------------------

### len()

Source: https://docs.rs/redb/4.1.0/redb/struct.MultimapValue.html

Returns the number of times this iterator will return Some(Ok(_)). Note that the iterator may return Some(Err(_)) more times than the value returned by len().

```APIDOC
## pub fn len(&self) -> u64

### Description
Returns the number of times this iterator will return `Some(Ok(_))`.

### Returns
- **u64** - The count of successful iterations.
```

--------------------------------

### iter

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Returns an iterator over the possibly contained value.

```APIDOC
## pub fn iter(&self) -> Iter<'_, T>

### Description
Returns an iterator over the possibly contained value. The iterator yields one value if the result is `Result::Ok`, otherwise none.
```

--------------------------------

### commit

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Commits the current transaction.

```APIDOC
## pub fn commit(self) -> Result<(), CommitError>

### Description
Commits the transaction, making all writes durable and visible to future transactions.
```

--------------------------------

### Provide fallback results with or_else

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Calls a closure to compute a fallback result if the current result is Err. This is lazily evaluated.

```rust
fn sq(x: u32) -> Result<u32, u32> { Ok(x * x) }
fn err(x: u32) -> Result<u32, u32> { Err(x) }

assert_eq!(Ok(2).or_else(sq).or_else(sq), Ok(2));
assert_eq!(Ok(2).or_else(err).or_else(sq), Ok(2));
assert_eq!(Err(3).or_else(sq).or_else(err), Ok(9));
assert_eq!(Err(3).or_else(err).or_else(err), Err(3));
```

--------------------------------

### rename_multimap_table

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Renames an existing multimap table.

```APIDOC
## pub fn rename_multimap_table( &self, definition: impl MultimapTableHandle, new_name: impl MultimapTableHandle, ) -> Result<(), TableError>

### Description
Renames the given multimap table to the new name provided.
```

--------------------------------

### cache_stats

Source: https://docs.rs/redb/4.1.0/redb/struct.Database.html

Retrieves information regarding the usage of the in-memory cache.

```APIDOC
### fn cache_stats(&self) -> CacheStats

Returns statistics about the current usage of the in-memory cache.
```

--------------------------------

### ReadOnlyUntypedTable Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.ReadOnlyUntypedTable.html

The structure definition for ReadOnlyUntypedTable.

```rust
pub struct ReadOnlyUntypedTable { /* private fields */ }
```

--------------------------------

### WriteTransaction Definition

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

The internal structure definition for a read/write transaction in redb.

```rust
pub struct WriteTransaction { /* private fields */ }
```

--------------------------------

### AccessGuard::value

Source: https://docs.rs/redb/4.1.0/redb/struct.AccessGuard.html

Access the stored value within the database.

```APIDOC
## pub fn value(&self) -> V::SelfType<'_>

### Description
Access the stored value associated with the AccessGuard instance.

### Returns
- **V::SelfType<'_>** - The stored value.
```

--------------------------------

### Chain fallible operations with and_then

Source: https://docs.rs/redb/4.1.0/redb/type.Result.html

Use and_then to chain operations that return a Result. The closure is only executed if the previous result is Ok.

```rust
assert_eq!(Ok(2).and_then(sq_then_to_string), Ok(4.to_string()));
assert_eq!(Ok(1_000_000).and_then(sq_then_to_string), Err("overflowed"));
assert_eq!(Err("not a number").and_then(sq_then_to_string), Err("not a number"));
```

```rust
use std::{io::ErrorKind, path::Path};

// Note: on Windows "/" maps to "C:\"
let root_modified_time = Path::new("/").metadata().and_then(|md| md.modified());
assert!(root_modified_time.is_ok());

let should_fail = Path::new("/bad/path").metadata().and_then(|md| md.modified());
assert!(should_fail.is_err());
assert_eq!(should_fail.unwrap_err().kind(), ErrorKind::NotFound);
```

--------------------------------

### delete_table

Source: https://docs.rs/redb/4.1.0/redb/struct.WriteTransaction.html

Deletes a table from the database.

```APIDOC
## pub fn delete_table( &self, definition: impl TableHandle, ) -> Result<bool, TableError>

### Description
Deletes the specified table. Returns a boolean indicating whether the table existed prior to deletion.
```
Tokens:
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