DuckDB

https://docs.rs/duckdb/latest/duckdb
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### Begin and Commit a Transaction in Rust

Source: https://docs.rs/duckdb/latest/duckdb/struct.Connection.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Shows how to start a new transaction using `Connection::transaction`. The example illustrates performing multiple queries within the transaction and explicitly committing it. If any part fails, the transaction will be rolled back by default when the `tx` variable is dropped.

```rust
fn perform_queries(conn: &mut Connection) -> Result<() as "std::result::Result<(), duckdb::Error>">
{
    let tx = conn.transaction()?;

    do_queries_part_1(&tx)?;
    do_queries_part_2(&tx)?;

    tx.commit()
}
```

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

### Example Searches for Type Conversion

Source: https://docs.rs/duckdb/latest/duckdb/vtab/arrow/fn.to_duckdb_logical_type.html?search=

These examples illustrate common search patterns for type conversions, such as converting standard library types or handling optional types.

```text
std::vec
```

```text
u32 -> bool
```

```text
Option<T>, (T -> U) -> Option<U>
```

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

### Example: Passing Positional Parameters to SQL Statements

Source: https://docs.rs/duckdb/latest/duckdb/trait.AppenderParams.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Demonstrates various ways to pass positional parameters to SQL statements using the `execute` method. Includes examples with `params!`, array literals, and slices of references.

```rust
fn update_rows(conn: &Connection) -> Result<()> {
    let mut stmt = conn.prepare("INSERT INTO test (a, b) VALUES (?, ?)")?;

    // Using `duckdb::params!`:
    stmt.execute(params![1i32, "blah"])?;

    // array literal — non-references
    stmt.execute([2i32, 3i32])?;

    // array literal — references
    stmt.execute(["foo", "bar"])?;

    // Slice literal, references:
    stmt.execute(&[&2i32, &3i32])?;

    // Note: The types behind the references don't have to be `Sized`
    stmt.execute(&["foo", "bar"])?;

    // However, this doesn't work (see above):
    // stmt.execute(&[1i32, 2i32])?;
    Ok(())
}
```

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

### Example Search: u32 to bool Conversion

Source: https://docs.rs/duckdb/latest/duckdb/constant.MAIN_DB.html?search=u32+-%3E+bool

This is an example search query demonstrating a common type conversion pattern in Rust.

```rust
u32 -> bool

```

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

### Example: Passing Positional Parameters to DuckDB

Source: https://docs.rs/duckdb/latest/duckdb/trait.Params.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Demonstrates various ways to pass positional parameters to SQL statements using the `execute` method. Includes examples with `duckdb::params!`, array literals (references and non-references), slice literals, and tuples.

```rust
fn update_rows(conn: &Connection) -> Result<()> {
    let mut stmt = conn.prepare("INSERT INTO test (a, b) VALUES (?, ?)")?;

    // Using `duckdb::params!`: 
    stmt.execute(params![1i32, "blah"])?;

    // array literal — non-references
    stmt.execute([2i32, 3i32])?;

    // array literal — references
    stmt.execute(["foo", "bar"])?;

    // Slice literal, references: 
    stmt.execute(&[&2i32, &3i32])?;

    // Note: The types behind the references don't have to be `Sized`
    stmt.execute(&["foo", "bar"])?;

    // Tuple of mixed types:
    stmt.execute((1i32, "blah"))?;

    // However, this doesn't work (see above):
    // stmt.execute(&[1i32, 2i32])?;
    Ok(())
}
```

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

### Begin an Unchecked Transaction in Rust

Source: https://docs.rs/duckdb/latest/duckdb/struct.Connection.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Demonstrates starting a transaction using `Connection::unchecked_transaction`. This method defers the check for nested transactions until runtime, unlike `Connection::transaction` which checks at compile time. The example shows performing queries and committing the transaction.

```rust
fn perform_queries(conn: Rc<Connection>) -> Result<() as "std::result::Result<(), duckdb::Error>">
{
    let tx = conn.unchecked_transaction()?;

    do_queries_part_1(&tx)?;
    do_queries_part_2(&tx)?;

    tx.commit()
}
```

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

### Example: Get column count

Source: https://docs.rs/duckdb/latest/duckdb/struct.CachedStatement.html?search=

Demonstrates two ways to get the column count: executing the statement first, or querying rows and then getting the count from the rows. This example requires a `Connection` object and a `Result` type.

```rust
fn get_column_count(conn: &Connection) -> Result<usize> {
    let mut stmt = conn.prepare("SELECT id, name FROM people")?;

    // Option 1: Execute first, then get column count
    stmt.execute([])?;
    let count = stmt.column_count();

    // Option 2: Get column count from rows (avoids borrowing issues)
    let mut stmt2 = conn.prepare("SELECT id, name FROM people")?;
    let rows = stmt2.query([])?;
    let count2 = rows.as_ref().unwrap().column_count();

    Ok(count)
}
```

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

### Handling File Metadata with `and_then`

Source: https://docs.rs/duckdb/latest/duckdb/type.Result.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Illustrates using `and_then` to chain fallible operations when working with file system metadata. This example shows how to get the modification time of the root directory and handle potential errors like a non-existent path.

```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);
```

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

### Profiling Search Examples

Source: https://docs.rs/duckdb/latest/duckdb/profiling/struct.ProfilingInfo.html?search=

Examples of how to structure search queries for profiling data.

```APIDOC
## Profiling Search Examples

This section provides examples of common search queries used for profiling.

### Example Searches

*   `std::vec`
*   `u32 -> bool`
*   `Option<T>, (T -> U) -> Option<U>`
```

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

### TableFunction Search Examples

Source: https://docs.rs/duckdb/latest/duckdb/vtab/struct.TableFunction.html?search=

Examples of how to search for table functions.

```APIDOC
## Search Table Functions

### Description
Provides examples of search queries for table functions.

### Example Searches
* `std::vec`
* `u32 -> bool`
* `Option<T>, (T -> U) -> Option<U>`
```

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

### Basic usage example

Source: https://docs.rs/duckdb/latest/duckdb/struct.AppenderParamsFromIter.html

Demonstrates how to use `params_from_iter` with a `BTreeSet` for a dynamic `IN` clause.

```APIDOC
## §Example

### §Basic usage

```rust
use duckdb::{Connection, Result, params_from_iter};
use std::collections::BTreeSet;

fn query(conn: &Connection, ids: &BTreeSet<String>) -> Result<()> {
    assert_eq!(ids.len(), 3, "Unrealistic sample code");

    let mut stmt = conn.prepare("SELECT * FROM users WHERE id IN (?, ?, ?)")?;
    let _rows = stmt.query(params_from_iter(ids.iter()))?;

    // use _rows...
    Ok(())
}
```
```

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

### Realistic use case example

Source: https://docs.rs/duckdb/latest/duckdb/struct.AppenderParamsFromIter.html

Illustrates using `ParamsFromIter` with `Statement::exists` for a dynamic number of parameters.

```APIDOC
### §Realistic use case

Here’s how you’d use `ParamsFromIter` to call [`Statement::exists`] with a dynamic number of parameters.

```rust
use duckdb::{Connection, Result};

pub fn any_active_users(conn: &Connection, usernames: &[String]) -> Result<bool> {
    if usernames.is_empty() {
        return Ok(false);
    }

    // Note: `repeat_vars` never returns anything attacker-controlled, so
    // it's fine to use it in a dynamically-built SQL string.
    let vars = repeat_vars(usernames.len());

    let sql = format!(
        // In practice this would probably be better as an `EXISTS` query.
        "SELECT 1 FROM user WHERE is_active AND name IN ({}) LIMIT 1",
        vars,
    );
    let mut stmt = conn.prepare(&sql)?;
    stmt.exists(duckdb::params_from_iter(usernames))
}

// Helper function to return a comma-separated sequence of `?`.
// - `repeat_vars(0) => panic!(...)
// - `repeat_vars(1) => "?"
// - `repeat_vars(2) => "?,""
// - `repeat_vars(3) => "?,?,?"
// - ...
fn repeat_vars(count: usize) -> String {
    assert_ne!(count, 0);
    let mut s = "?,".repeat(count);
    // Remove trailing comma
    s.pop();
    s
}
```

That is fairly complex, and even so would need even more work to be fully production-ready:
  * production code should ensure `usernames` isn’t so large that it will surpass `conn.limit(Limit::SQLITE_LIMIT_VARIABLE_NUMBER)`), chunking if too large. (Note that the limits api requires duckdb to have the “limits” feature).
  * `repeat_vars` can be implemented in a way that avoids needing to allocate a String.
  * Etc…


This complexity reflects the fact that `ParamsFromIter` is mainly intended for advanced use cases — most of the time you should know how many parameters you have statically (and if you don’t, you’re either doing something tricky, or should take a moment to think about the design).
```

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

### Example Usage

Source: https://docs.rs/duckdb/latest/duckdb/struct.AppenderParamsFromIter.html?search=

Demonstrates how to use AppenderParamsFromIter with params_from_iter for dynamic SQL parameter binding.

```APIDOC
## §Example

### §Basic usage
```rust
use duckdb::{Connection, Result, params_from_iter};
use std::collections::BTreeSet;

fn query(conn: &Connection, ids: &BTreeSet<String>) -> Result<()> {
    assert_eq!(ids.len(), 3, "Unrealistic sample code");

    let mut stmt = conn.prepare("SELECT * FROM users WHERE id IN (?, ?, ?)")?;
    let _rows = stmt.query(params_from_iter(ids.iter()))?;

    // use _rows...
    Ok(())
}
```

### §Realistic use case
Here’s how you’d use `ParamsFromIter` to call [`Statement::exists`] with a dynamic number of parameters.
```rust
use duckdb::{Connection, Result};

pub fn any_active_users(conn: &Connection, usernames: &[String]) -> Result<bool> {
    if usernames.is_empty() {
        return Ok(false);
    }

    // Note: `repeat_vars` never returns anything attacker-controlled, so
    // it's fine to use it in a dynamically-built SQL string.
    let vars = repeat_vars(usernames.len());

    let sql = format!(
        // In practice this would probably be better as an `EXISTS` query.
        "SELECT 1 FROM user WHERE is_active AND name IN ({}) LIMIT 1",
        vars,
    );
    let mut stmt = conn.prepare(&sql)?;
    stmt.exists(duckdb::params_from_iter(usernames))
}

// Helper function to return a comma-separated sequence of `?`.
// - `repeat_vars(0) => panic!(...)
// - `repeat_vars(1) => "?"
// - `repeat_vars(2) => "?,?"
// - `repeat_vars(3) => "?,?,?"
// - ...
fn repeat_vars(count: usize) -> String {
    assert_ne!(count, 0);
    let mut s = "?,".repeat(count);
    // Remove trailing comma
    s.pop();
    s
}
```
```

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

### Basic Usage Example

Source: https://docs.rs/duckdb/latest/duckdb/index.html

Demonstrates opening an in-memory database, creating a table, inserting data, querying data, and querying data using Arrow RecordBatches.

```APIDOC
## Basic Usage Example

This example demonstrates the fundamental operations of the duckdb-rs crate, including database connection, table creation, data manipulation, and querying.

### Code

```rust
use duckdb::{params, Connection, Result};
use duckdb::arrow::record_batch::RecordBatch;
use duckdb::arrow::util::pretty::print_batches;

#[derive(Debug)]
struct Person {
    id: i32,
    name: String,
    data: Option<Vec<u8>>,
}

fn main() -> Result<()> {
    let conn = Connection::open_in_memory()?;

    conn.execute_batch(
        r"CREATE SEQUENCE seq;
          CREATE TABLE person (
                  id              INTEGER PRIMARY KEY DEFAULT NEXTVAL('seq'),
                  name            TEXT NOT NULL,
                  data            BLOB
                  );
         ")?;
    let me = Person {
        id: 0,
        name: "Steven".to_string(),
        data: None,
    };
    conn.execute(
        "INSERT INTO person (name, data) VALUES (?, ?)",
        params![me.name, me.data],
    )?;

    let mut stmt = conn.prepare("SELECT id, name, data FROM person")?;
    let person_iter = stmt.query_map([], |row| {
        Ok(Person {
            id: row.get(0)?,
            name: row.get(1)?,
            data: row.get(2)?,
        })
    })?;

    for person in person_iter {
        println!("Found person {:?}", person.unwrap());
    }

    // query table by arrow
    let rbs: Vec<RecordBatch> = stmt.query_arrow([])?.collect();
    print_batches(&rbs);
    Ok(())
}
```
```

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

### Get offset and length for a list entry

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.ListVector.html?search=

Retrieves the offset and length for a given entry index in the list vector. This allows access to the start and size of each list element.

```rust
pub fn get_entry(&self, idx: usize) -> (usize, usize)
```

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

### Example: Basic usage

Source: https://docs.rs/duckdb/latest/duckdb/struct.AppenderParamsFromIter.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Demonstrates basic usage of `params_from_iter` with a `BTreeSet` for a prepared statement with a fixed number of parameters.

```APIDOC
## §Example
### §Basic usage
```rust
use duckdb::{Connection, Result, params_from_iter};
use std::collections::BTreeSet;

fn query(conn: &Connection, ids: &BTreeSet<String>) -> Result<()> {
    assert_eq!(ids.len(), 3, "Unrealistic sample code");

    let mut stmt = conn.prepare("SELECT * FROM users WHERE id IN (?, ?, ?)")?;
    let _rows = stmt.query(params_from_iter(ids.iter()))?;

    // use _rows...
    Ok(())
}
```
```

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

### Pointable::init

Source: https://docs.rs/duckdb/latest/duckdb/struct.Arrow.html?search=std%3A%3Avec

Initializes a new instance at a given memory location.

```APIDOC
## unsafe fn init(init: <T as Pointable>::Init) -> usize

### Description
Initializes a new instance with the given initializer. This function is unsafe as it involves direct memory manipulation.

### Parameters
- `init`: The initializer value for the new instance.

### Returns
The starting address of the initialized memory as a `usize`.
```

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

### OrderedMap Search Examples

Source: https://docs.rs/duckdb/latest/duckdb/types/struct.OrderedMap.html?search=

Demonstrates various ways to search for elements within an OrderedMap.

```APIDOC
## Search Examples

This section provides examples of how to search within an OrderedMap.

### Example Searches

*   `std::vec`
*   `u32 -> bool`
*   `Option<T>, (T -> U) -> Option<U>`
```

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

### Begin and Commit a Transaction in Rust

Source: https://docs.rs/duckdb/latest/duckdb/struct.Connection.html?search=std%3A%3Avec

Illustrates how to start a new transaction and ensure its commit. The transaction defaults to rollback on drop, so `commit()` must be explicitly called for persistence.

```rust
fn perform_queries(conn: &mut Connection) -> Result<()>
{
    let tx = conn.transaction()?;

    do_queries_part_1(&tx)?;
    do_queries_part_2(&tx)?;

    tx.commit()
}
```

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

### Example Search: Option<T>, (T -> U) -> Option<U>

Source: https://docs.rs/duckdb/latest/duckdb/constant.MAIN_DB.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Illustrates a common search pattern for function signatures involving Option types and function transformations.

```text
Option<T>, (T -> U) -> Option<U>

```

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

### get

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html?search=std%3A%3Avec

Gets a reference to the enum key from the given memory location.

```APIDOC
## unsafe fn get<'a>(ptr: *const u8) -> &'a T

### Description
Get a reference to the key from the given memory location.

### Method
`get`

### Parameters
- **ptr** (*const u8): A constant pointer to the memory location.

### Response
#### Success Response (&'a T)
- **&'a T**: An immutable reference to the key.
```

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

### init

Source: https://docs.rs/duckdb/latest/duckdb/struct.Statement.html?search=u32+-%3E+bool

Initializes a with the given initializer.

```APIDOC
## init

### Description
Initializes a with the given initializer.

### Signature
`unsafe fn init(init: <T as Pointable>::Init) -> usize`
```

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

### init

Source: https://docs.rs/duckdb/latest/duckdb/struct.Polars.html?search=std%3A%3Avec

Initializes a with the given initializer.

```APIDOC
#### unsafe fn init(init: <T as Pointable>::Init) -> usize
Initializes a with the given initializer. Read more
```

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

### get

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html

Gets a reference to the key from the given memory location. This is an unsafe operation.

```APIDOC
## unsafe fn get<'a>(ptr: *const u8) -> &'a T

### Description
Get a reference to the key from the given memory location.

### Method
`get`
```

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

### Example: Execute with positional parameters

Source: https://docs.rs/duckdb/latest/duckdb/struct.CachedStatement.html?search=

Demonstrates executing a prepared statement with positional parameters using the `duckdb::params!` macro or by passing slices or arrays. This is useful for updating or inserting data.

```rust
fn update_rows(conn: &Connection) -> Result<()> {
    let mut stmt = conn.prepare("UPDATE foo SET bar = 'baz' WHERE qux = ?")?;
    // The `duckdb::params!` macro is mostly useful when the parameters do not
    // all have the same type, or if there are more than 32 parameters
    // at once.
    stmt.execute(params![1i32])?;
    // However, it's not required, many cases are fine as:
    stmt.execute(&[&2i32])?;
    // Or even:
    stmt.execute([2i32])?;
    Ok(())
}
```

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

### VScalar Implementation Example

Source: https://docs.rs/duckdb/latest/duckdb/vscalar/trait.VScalar.html?search=

Example of implementing the VScalar trait for a type T that also implements VArrowScalar. This shows how the State type is derived.

```rust
impl<T> VScalar for T
where T: VArrowScalar,
{
    type State = <T as VArrowScalar>::State
```

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

### unsafe fn get<'a>(ptr: *const u8) -> &'a T

Source: https://docs.rs/duckdb/latest/duckdb/enum.ErrorCode.html

Gets a reference to the key from the memory location pointed to by `ptr`. This is an unsafe operation.

```APIDOC
## unsafe fn get<'a>(ptr: *const u8) -> &'a T

### Description
Get a reference to the key from the given memory location.

### Parameters
* **ptr** (*const u8) - A constant pointer to the memory location.

### Returns
* &'a T - A reference to the key.
```

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

### init

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html

Initializes the key in the given memory location. This is an unsafe operation.

```APIDOC
## unsafe fn init(&self, ptr: *mut u8)

### Description
Initialize the key in the given memory location.

### Method
`init`
```

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

### Example: Execute without parameters

Source: https://docs.rs/duckdb/latest/duckdb/struct.CachedStatement.html?search=

Shows how to execute a prepared statement that requires no parameters, such as a DELETE statement affecting all rows.

```rust
fn delete_all(conn: &Connection) -> Result<()> {
    let mut stmt = conn.prepare("DELETE FROM users")?;
    stmt.execute([])?;
    Ok(())
}
```

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

### Get Thread-Local Init Data

Source: https://docs.rs/duckdb/latest/duckdb/vtab/struct.TableFunctionInfo.html?search=

Gets the thread-local init data that was set by `InitInfo::set_init_data` during the `local_init` phase. This returns a raw mutable pointer.

```rust
pub fn get_local_init_data<T>(&self) -> *mut T
```

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

### Init

Source: https://docs.rs/duckdb/latest/duckdb/struct.Statement.html?search=u32+-%3E+bool

The type for initializers.

```APIDOC
## Init

### Description
The type for initializers.

### Associated Type
`type Init = T`
```

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

### Init

Source: https://docs.rs/duckdb/latest/duckdb/struct.Polars.html?search=std%3A%3Avec

The type for initializers.

```APIDOC
#### type Init = T
The type for initializers.
```

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

### Get Bind Data from BindInfo

Source: https://docs.rs/duckdb/latest/duckdb/vtab/struct.InitInfo.html

Gets the bind data set by `BindInfo::set_bind_data` during the bind. The bind data should be considered read-only; use init data for state tracking.

```rust
pub fn get_bind_data<T>(&self) -> *const T
```

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

### ListVector Methods

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.ListVector.html?search=

Provides methods for interacting with ListVector, including getting its length, checking if it's empty, accessing child vectors, setting and getting entries, and managing nulls and length.

```APIDOC
## ListVector
duckdb::core

A list vector borrowed from a `DataChunkHandle`.
Stores list entry offsets and lengths; elements live in a separate child vector.

### Methods

#### `len(&self) -> usize`
Returns the number of entries in the list vector.

#### `is_empty(&self) -> bool`
Returns true if the list vector is empty.

#### `child(&self, capacity: usize) -> FlatVector<'a>`
Returns the child vector.

#### `struct_child(&self, capacity: usize) -> StructVector<'a>`
Take the child as StructVector.

#### `array_child(&self) -> ArrayVector<'a>`
Take the child as ArrayVector.

#### `list_child(&self) -> ListVector<'a>`
Take the child as ListVector.

#### `set_child<T: Copy>(&self, data: &[T])`
Set primitive data to the child node.

#### `set_entry(&mut self, idx: usize, offset: usize, length: usize)`
Set offset and length to the entry.

#### `get_entry(&self, idx: usize) -> (usize, usize)`
Get offset and length for the entry at index.

#### `set_null(&mut self, row: usize)`
Set row as null

#### `set_len(&self, new_len: usize)`
Set the length of the list vector.
```

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

### Pointable Init

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html?search=

The type for initializers.

```APIDOC
## type Init = T

### Description
The type for initializers.

### Method
`Init`
```

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

### Basic Usage Example

Source: https://docs.rs/duckdb/latest/duckdb/struct.ParamsFromIter.html?search=u32+-%3E+bool

Demonstrates a basic usage scenario of `params_from_iter` with a `BTreeSet<String>` to query a database where the number of parameters in the `WHERE` clause is dynamically determined.

```APIDOC
## §Example
### §Basic usage

```rust
use duckdb::{Connection, Result, params_from_iter};
use std::collections::BTreeSet;

fn query(conn: &Connection, ids: &BTreeSet<String>) -> Result<()> {
    assert_eq!(ids.len(), 3, "Unrealistic sample code");

    let mut stmt = conn.prepare("SELECT * FROM users WHERE id IN (?, ?, ?)")?;
    let _rows = stmt.query(params_from_iter(ids.iter()))?;

    // use _rows...
    Ok(())
}
```
```

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

### type_id

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html?search=std%3A%3Avec

Gets the TypeId of the enum value.

```APIDOC
## fn type_id(&self) -> TypeId

### Description
Gets the `TypeId` of `self`.

### Method
`type_id`

### Parameters
None

### Response
#### Success Response (TypeId)
- **TypeId**: The unique identifier for the type.
```

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

### LogicalTypeHandle::id

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.LogicalTypeHandle.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Gets the LogicalTypeId of the handle.

```APIDOC
## LogicalTypeHandle::id

### Description
Logical type ID

### Signature
`pub fn id(&self) -> LogicalTypeId`
```

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

### Example: Passing Positional Parameters

Source: https://docs.rs/duckdb/latest/duckdb/trait.Params.html?search=

Demonstrates various ways to pass positional parameters to SQL statements using the `params!` macro, array literals, and tuples. Ensure correct usage based on parameter count and type heterogeneity.

```rust
fn update_rows(conn: &Connection) -> Result<()> {
    let mut stmt = conn.prepare("INSERT INTO test (a, b) VALUES (?, ?)")?;

    // Using `duckdb::params!`: 
    stmt.execute(params![1i32, "blah"])?;

    // array literal — non-references
    stmt.execute([2i32, 3i32])?;

    // array literal — references
    stmt.execute(["foo", "bar"])?;

    // Slice literal, references:
    stmt.execute(&[&2i32, &3i32])?;

    // Note: The types behind the references don't have to be `Sized`
    stmt.execute(&["foo", "bar"])?;

    // Tuple of mixed types:
    stmt.execute((1i32, "blah"))?;

    // However, this doesn't work (see above):
    // stmt.execute(&[1i32, 2i32])?;
    Ok(())
}
```

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

### Rows::next

Source: https://docs.rs/duckdb/latest/duckdb/struct.Rows.html

Attempt to get the next row from the query. Returns `Ok(Some(Row))` if there is another row, `Err(...)` if there was an error getting the next row, and `Ok(None)` if all rows have been retrieved. This method is part of the FallibleStreamingIterator trait.

```APIDOC
## pub fn next(&mut self) -> Result<Option<&Row<'stmt>>>

### Description
Attempt to get the next row from the query. Returns `Ok(Some(Row))` if there is another row, `Err(...)` if there was an error getting the next row, and `Ok(None)` if all rows have been retrieved.

### Note
This interface is not compatible with Rust’s `Iterator` trait, because the lifetime of the returned row is tied to the lifetime of `self`. This is a fallible “streaming iterator”. For a more natural interface, consider using `query_map` or `query_and_then` instead, which return types that implement `Iterator`.
```

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

### Init

Source: https://docs.rs/duckdb/latest/duckdb/struct.Row.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Type alias for initializers.

```APIDOC
## type Init = T

### Description
The type for initializers.

### Type Alias
`Init`
```

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

### size

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html?search=std%3A%3Avec

Gets the size of the enum key in bytes.

```APIDOC
## fn size(&self) -> usize

### Description
The size of the key in bytes.

### Method
`size`

### Parameters
None

### Response
#### Success Response (usize)
- **usize**: The size of the key in bytes.
```

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

### Prepare and Execute SQL Statements

Source: https://docs.rs/duckdb/latest/duckdb/struct.Connection.html

Prepare a SQL statement once using `prepare` and then execute it multiple times. This is efficient for repeated operations like inserting multiple rows.

```rust
fn insert_new_people(conn: &Connection) -> Result<()> {
    let mut stmt = conn.prepare("INSERT INTO People (name) VALUES (?)")?;
    stmt.execute(["Joe Smith"])?;
    stmt.execute(["Bob Jones"])?;
    Ok(())
}
```

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

### Begin and Commit an Unchecked Transaction

Source: https://docs.rs/duckdb/latest/duckdb/struct.Connection.html?search=u32+-%3E+bool

Demonstrates starting a transaction that defers runtime checks for nested transactions. This is useful when the compile-time check of `Connection::transaction` is not desired or possible. The transaction rolls back on drop if not committed.

```rust
fn perform_queries(conn: Rc<Connection>) -> Result<() as _> {
    let tx = conn.unchecked_transaction()?;

    do_queries_part_1(&tx)?;
    do_queries_part_2(&tx)?;

    tx.commit()
}
```

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

### align

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html?search=std%3A%3Avec

Gets the required alignment for the enum key.

```APIDOC
## fn align() -> usize

### Description
The alignment necessary for the key. Must return a power of two.

### Method
`align`

### Parameters
None

### Response
#### Success Response (usize)
- **usize**: The alignment value.
```

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

### init

Source: https://docs.rs/duckdb/latest/duckdb/struct.Arrow.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Initializes a value at a given memory location.

```APIDOC
## unsafe fn init(init: <T as Pointable>::Init) -> usize

### Description
Initializes a value in memory with the given initializer. This operation is unsafe.

### Parameters
- `init`: The initializer value for the type `T`.

### Returns
The pointer to the newly initialized value.
```

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

### Type Identification

Source: https://docs.rs/duckdb/latest/duckdb/struct.ArrowStream.html

Method to get the TypeId of a value.

```APIDOC
## fn type_id(&self) -> TypeId

### Description
Gets the `TypeId` of `self`.

### Method
`type_id`

### Response
- **TypeId**: The unique identifier for the type of `self`.
```

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

### Basic DuckDB Operations in Rust

Source: https://docs.rs/duckdb/latest/duckdb/index.html?search=std%3A%3Avec

Demonstrates opening an in-memory database, creating a table, inserting data, querying rows, and retrieving results as Arrow RecordBatches. Ensure you have the necessary dependencies and imports for duckdb and arrow.

```rust
use duckdb::{params, Connection, Result};
use duckdb::arrow::record_batch::RecordBatch;
use duckdb::arrow::util::pretty::print_batches;

#[derive(Debug)]
struct Person {
    id: i32,
    name: String,
    data: Option<Vec<u8>>,
}

fn main() -> Result<()> {
    let conn = Connection::open_in_memory()?;

    conn.execute_batch(
        r"CREATE SEQUENCE seq;
          CREATE TABLE person (
                  id              INTEGER PRIMARY KEY DEFAULT NEXTVAL('seq'),
                  name            TEXT NOT NULL,
                  data            BLOB
                  );
         ")?;
    let me = Person {
        id: 0,
        name: "Steven".to_string(),
        data: None,
    };
    conn.execute(
        "INSERT INTO person (name, data) VALUES (?, ?)",
        params![me.name, me.data],
    )?;

    let mut stmt = conn.prepare("SELECT id, name, data FROM person")?;
    let person_iter = stmt.query_map([], |row| {
        Ok(Person {
            id: row.get(0)?,
            name: row.get(1)?,
            data: row.get(2)?,
        })
    })?;

    for person in person_iter {
        println!("Found person {:?}", person.unwrap());
    }

    // query table by arrow
    let rbs: Vec<RecordBatch> = stmt.query_arrow([])?.collect();
    print_batches(&rbs);
    Ok(())
}

```

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

### DataChunkHandle::num_columns

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.DataChunkHandle.html?search=u32+-%3E+bool

Gets the number of columns in the DataChunkHandle.

```APIDOC
## DataChunkHandle::num_columns

### Description
Get the number of columns in this DataChunkHandle.

### Signature
`pub fn num_columns(&self) -> usize`
```

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

### Get Version

Source: https://docs.rs/duckdb/latest/duckdb/struct.Connection.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Retrieves the version string of the DuckDB library.

```APIDOC
## pub fn version(&self) -> Result<String>

### Description
Returns the version of the DuckDB library
```

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

### impl<T> Any for T

Source: https://docs.rs/duckdb/latest/duckdb/struct.ArrowStream.html?search=std%3A%3Avec

Provides the `type_id` method to get the `TypeId` of `self`.

```APIDOC
## fn type_id(&self) -> TypeId

### Description
Gets the `TypeId` of `self`.

### Returns
- **TypeId**: The unique identifier for the type of `self`.
```

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

### InitInfo Methods

Source: https://docs.rs/duckdb/latest/duckdb/vtab/struct.InitInfo.html?search=u32+-%3E+bool

This section details the methods available on the InitInfo struct for managing initialization data and configuration.

```APIDOC
## InitInfo

An interface to store and retrieve data during the function init stage.

### Methods

#### `set_init_data(&self, data: *mut c_void, freeer: Option<unsafe extern "C" fn(*mut c_void)>)`

Sets initialization data and a corresponding freeer function.

#### `get_column_indices(&self) -> Vec<idx_t>`

Returns the column indices of the projected columns at the specified positions. This function must be used if projection pushdown is enabled to figure out which columns to emit.

* **Returns**: The column indices at which to get the projected column index.

#### `get_extra_info<T>(&self) -> *const T`

Retrieves the extra info of the function as set in `TableFunction::set_extra_info`.

#### `get_bind_data<T>(&self) -> *const T`

Gets the bind data set by `BindInfo::set_bind_data` during the bind. Note that the bind data should be considered as read-only. For tracking state, use the init data instead.

* **Returns**: The bind data object.

#### `set_max_threads(&self, max_threads: idx_t)`

Sets how many threads can process this table function in parallel (default: 1).

* **Arguments**:
  * `max_threads`: The maximum amount of threads that can process this table function.

#### `set_error(&self, error: &str)`

Report that an error has occurred while calling init.

* **Arguments**:
  * `error`: The error message.
```

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

### from

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html?search=std%3A%3Avec

Creates a new instance from a given value.

```APIDOC
## fn from(t: T) -> T

### Description
Returns the argument unchanged.

### Method
`from`

### Parameters
- **t** (T): The value to create the instance from.

### Response
#### Success Response (T)
- **T**: The newly created instance.
```

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

### deref_mut

Source: https://docs.rs/duckdb/latest/duckdb/struct.Arrow.html?search=u32+-%3E+bool

Dereferences a pointer to get a mutable reference to the value.

```APIDOC
## unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

### Description
Mutably dereferences the given pointer (`ptr`) to obtain a mutable reference (`&'a mut T`) to the value it points to.

### Parameters
- `ptr`: A `usize` representing the pointer to the value.

### Returns
- `&'a mut T`: A mutable reference to the value.

### Safety
This function is unsafe. The caller must ensure that `ptr` is a valid pointer to a value of type `T` that lives for at least `'a`, and that no other references to the value exist.
```

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

### deref

Source: https://docs.rs/duckdb/latest/duckdb/struct.Arrow.html?search=u32+-%3E+bool

Dereferences a pointer to get an immutable reference to the value.

```APIDOC
## unsafe fn deref<'a>(ptr: usize) -> &'a T

### Description
Dereferences the given pointer (`ptr`) to obtain an immutable reference (`&'a T`) to the value it points to.

### Parameters
- `ptr`: A `usize` representing the pointer to the value.

### Returns
- `&'a T`: An immutable reference to the value.

### Safety
This function is unsafe. The caller must ensure that `ptr` is a valid pointer to a value of type `T` that lives for at least `'a`.
```

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

### deref_mut

Source: https://docs.rs/duckdb/latest/duckdb/struct.Arrow.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Dereferences a raw pointer to get a mutable reference.

```APIDOC
## unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

### Description
Dereferences the given raw pointer to obtain a mutable reference to the value. This operation is unsafe.

### Parameters
- `ptr`: The raw pointer (as a `usize`) to dereference.

### Returns
A mutable reference `&'a mut T` to the value at the pointer.
```

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

### Begin Transaction

Source: https://docs.rs/duckdb/latest/duckdb/struct.Connection.html

Starts a new deferred transaction. By default, transactions roll back when dropped. Call `commit` or set `DropBehavior::Commit` to persist changes.

```rust
fn perform_queries(conn: &mut Connection) -> Result<()> {
    let tx = conn.transaction()?;

    do_queries_part_1(&tx)?;
    do_queries_part_2(&tx)?;

    tx.commit()
}
```

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

### deref

Source: https://docs.rs/duckdb/latest/duckdb/struct.Arrow.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Dereferences a raw pointer to get an immutable reference.

```APIDOC
## unsafe fn deref<'a>(ptr: usize) -> &'a T

### Description
Dereferences the given raw pointer to obtain an immutable reference to the value. This operation is unsafe.

### Parameters
- `ptr`: The raw pointer (as a `usize`) to dereference.

### Returns
An immutable reference `&'a T` to the value at the pointer.
```

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

### Basic DuckDB Operations in Rust

Source: https://docs.rs/duckdb/latest/duckdb/index.html

Demonstrates opening an in-memory database, creating a table, inserting data, querying rows, and querying data as Arrow RecordBatches. Requires the 'arrow' feature flag.

```rust
use duckdb::{params, Connection, Result};
use duckdb::arrow::record_batch::RecordBatch;
use duckdb::arrow::util::pretty::print_batches;

#[derive(Debug)]
struct Person {
    id: i32,
    name: String,
    data: Option<Vec<u8>>,
}

fn main() -> Result<()> {
    let conn = Connection::open_in_memory()?;

    conn.execute_batch(
        r"CREATE SEQUENCE seq;
          CREATE TABLE person (
                  id              INTEGER PRIMARY KEY DEFAULT NEXTVAL('seq'),
                  name            TEXT NOT NULL,
                  data            BLOB
                  );
         ")?;
    let me = Person {
        id: 0,
        name: "Steven".to_string(),
        data: None,
    };
    conn.execute(
        "INSERT INTO person (name, data) VALUES (?, ?)",
        params![me.name, me.data],
    )?;

    let mut stmt = conn.prepare("SELECT id, name, data FROM person")?;
    let person_iter = stmt.query_map([], |row| {
        Ok(Person {
            id: row.get(0)?,
            name: row.get(1)?,
            data: row.get(2)?,
        })
    })?;

    for person in person_iter {
        println!("Found person {:?}", person.unwrap());
    }

    // query table by arrow
    let rbs: Vec<RecordBatch> = stmt.query_arrow([])?.collect();
    print_batches(&rbs);
    Ok(())
}
```

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

### Low-Level Parameter Binding and Query Execution

Source: https://docs.rs/duckdb/latest/duckdb/struct.CachedStatement.html?search=u32+-%3E+bool

Demonstrates the low-level API for binding parameters individually and then executing a query. Use this for advanced scenarios like gaps in parameters or mixed parameter types.

```rust
fn query(conn: &Connection) -> Result<()>
{
    let mut stmt = conn.prepare("SELECT * FROM test WHERE name = ? AND value > ?2")?;
    stmt.raw_bind_parameter(1, "foo")?;
    stmt.raw_bind_parameter(2, 100)?;
    let mut rows = stmt.raw_query();
    while let Some(row) = rows.next()? {
        // ...
    }
    Ok(())
}
```

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

### fn type_id(&self) -> TypeId

Source: https://docs.rs/duckdb/latest/duckdb/struct.Arrow.html?search=

Gets the TypeId of self.

```APIDOC
## fn type_id(&self) -> TypeId

### Description
Gets the `TypeId` of `self`.

### Returns
- TypeId: The unique identifier for the type of `self`.
```

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

### init

Source: https://docs.rs/duckdb/latest/duckdb/types/enum.ValueRef.html?search=std%3A%3Avec

Initializes the enum key in the given memory location.

```APIDOC
## unsafe fn init(&self, ptr: *mut u8)

### Description
Initialize the key in the given memory location.

### Method
`init`

### Parameters
- **ptr** (*mut u8): A mutable pointer to the memory location to initialize.

### Response
None
```

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

### LogicalTypeHandle::child

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.LogicalTypeHandle.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Gets a child logical type by its index.

```APIDOC
## LogicalTypeHandle::child

### Description
Logical type child by idx

### Signature
`pub fn child(&self, idx: usize) -> Self`
```

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

### Example: Realistic use case

Source: https://docs.rs/duckdb/latest/duckdb/struct.AppenderParamsFromIter.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Illustrates a more realistic use case for `AppenderParamsFromIter` with dynamically generated SQL, using `Statement::exists` and a dynamic number of parameters.

```APIDOC
## §Realistic use case
Here’s how you’d use `ParamsFromIter` to call [`Statement::exists`] with a dynamic number of parameters.
```rust
use duckdb::{Connection, Result};

pub fn any_active_users(conn: &Connection, usernames: &[String]) -> Result<bool> {
    if usernames.is_empty() {
        return Ok(false);
    }

    // Note: `repeat_vars` never returns anything attacker-controlled, so
    // it's fine to use it in a dynamically-built SQL string.
    let vars = repeat_vars(usernames.len());

    let sql = format!(
        // In practice this would probably be better as an `EXISTS` query.
        "SELECT 1 FROM user WHERE is_active AND name IN ({}) LIMIT 1",
        vars,
    );
    let mut stmt = conn.prepare(&sql)?;
    stmt.exists(duckdb::params_from_iter(usernames))
}

// Helper function to return a comma-separated sequence of `?`.
// - `repeat_vars(0) => panic!(...)
// - `repeat_vars(1) => "?"
// - `repeat_vars(2) => "?,""
// - `repeat_vars(3) => "?,?,?"
// - ...
fn repeat_vars(count: usize) -> String {
    assert_ne!(count, 0);
    let mut s = "?,".repeat(count);
    // Remove trailing comma
    s.pop();
    s
}
```

That is fairly complex, and even so would need even more work to be fully production-ready:
  * production code should ensure `usernames` isn’t so large that it will surpass `conn.limit(Limit::SQLITE_LIMIT_VARIABLE_NUMBER)`), chunking if too large. (Note that the limits api requires duckdb to have the “limits” feature).
  * `repeat_vars` can be implemented in a way that avoids needing to allocate a String.
  * Etc…


This complexity reflects the fact that `ParamsFromIter` is mainly intended for advanced use cases — most of the time you should know how many parameters you have statically (and if you don’t, you’re either doing something tricky, or should take a moment to think about the design).
```

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

### LogicalTypeHandle::num_children

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.LogicalTypeHandle.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Gets the number of children for the logical type.

```APIDOC
## LogicalTypeHandle::num_children

### Description
Logical type children num

### Signature
`pub fn num_children(&self) -> usize`
```

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

### InitInfo Methods

Source: https://docs.rs/duckdb/latest/duckdb/vtab/struct.InitInfo.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

This section details the public methods available on the InitInfo struct for interacting with initialization data and settings.

```APIDOC
## InitInfo

An interface to store and retrieve data during the function init stage.

### Methods

#### `set_init_data(&self, data: *mut c_void, freeer: Option<unsafe extern "C" fn(*mut c_void)>)`

Sets initialization data and a corresponding freeer function.

#### `get_column_indices(&self) -> Vec<idx_t>`

Returns the column indices of the projected columns at the specified positions. This function must be used if projection pushdown is enabled to figure out which columns to emit.

Returns: The column indices at which to get the projected column index.

#### `get_extra_info<T>(&self) -> *const T`

Retrieves the extra info of the function as set in `TableFunction::set_extra_info`.

#### `get_bind_data<T>(&self) -> *const T`

Gets the bind data set by `BindInfo::set_bind_data` during the bind. Note that the bind data should be considered as read-only. For tracking state, use the init data instead.

Arguments:
  * `returns`: The bind data object.

#### `set_max_threads(&self, max_threads: idx_t)`

Sets how many threads can process this table function in parallel (default: 1).

Arguments:
  * `max_threads`: The maximum amount of threads that can process this table function.

#### `set_error(&self, error: &str)`

Report that an error has occurred while calling init.

Arguments:
  * `error`: The error message.
```

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

### LogicalTypeHandle::try_id

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.LogicalTypeHandle.html?search=Option%3CT%3E%2C+%28T+-%3E+U%29+-%3E+Option%3CU%3E

Attempts to get the LogicalTypeId, with forward-compatibility awareness.

```APIDOC
## LogicalTypeHandle::try_id

### Description
Logical type ID, with forward-compatibility awareness.
Returns `Ok(LogicalTypeId)` for all known ids (including `Invalid`), and `Err(raw_id)` when DuckDB returns an id this wrapper does not yet recognize.

### Signature
`pub fn try_id(&self) -> Result<LogicalTypeId, u32>`
```

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

### Pointable::init

Source: https://docs.rs/duckdb/latest/duckdb/struct.AndThenRows.html?search=u32+-%3E+bool

Initializes a value in memory at a given alignment.

```APIDOC
## unsafe fn init(init: <T as Pointable>::Init) -> usize

### Description
Initializes a value of type `T` using the provided initializer and returns the memory address where it was placed. This is an unsafe operation.

### Parameters
- `init`: The initializer value for type `T`.

### Returns
The memory address (as `usize`) of the initialized value.
```

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

### Get FlatVector Capacity

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.FlatVector.html

Returns the total capacity of the FlatVector.

```rust
pub fn capacity(&self) -> usize
```

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

### DataChunkHandle::get_ptr

Source: https://docs.rs/duckdb/latest/duckdb/core/struct.DataChunkHandle.html

Gets the raw pointer to the underlying duckdb_data_chunk.

```APIDOC
## DataChunkHandle::get_ptr

### Description
Get the ptr of duckdb_data_chunk in this DataChunkHandle.

### Signature
```rust
pub fn get_ptr(&self) -> duckdb_data_chunk
```
```

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

### Realistic Use Case Example

Source: https://docs.rs/duckdb/latest/duckdb/struct.ParamsFromIter.html?search=u32+-%3E+bool

Illustrates a more realistic use case for `ParamsFromIter` in the `any_active_users` function, which checks for active users by name using a dynamically generated SQL query with a variable number of parameters.

```APIDOC
## §Realistic use case
Here’s how you’d use `ParamsFromIter` to call `Statement::exists` with a dynamic number of parameters.

```rust
use duckdb::{Connection, Result};

pub fn any_active_users(conn: &Connection, usernames: &[String]) -> Result<bool> {
    if usernames.is_empty() {
        return Ok(false);
    }

    // Note: `repeat_vars` never returns anything attacker-controlled, so
    // it's fine to use it in a dynamically-built SQL string.
    let vars = repeat_vars(usernames.len());

    let sql = format!(
        // In practice this would probably be better as an `EXISTS` query.
        "SELECT 1 FROM user WHERE is_active AND name IN ({}) LIMIT 1",
        vars,
    );
    let mut stmt = conn.prepare(&sql)?;
    stmt.exists(duckdb::params_from_iter(usernames))
}

// Helper function to return a comma-separated sequence of `?`.
// - `repeat_vars(0) => panic!(...)
// - `repeat_vars(1) => "?"
// - `repeat_vars(2) => "?,""
// - `repeat_vars(3) => "?,?,?"
// - ...
fn repeat_vars(count: usize) -> String {
    assert_ne!(count, 0);
    let mut s = "?,".repeat(count);
    // Remove trailing comma
    s.pop();
    s
}
```

That is fairly complex, and even so would need even more work to be fully production-ready:
  * production code should ensure `usernames` isn’t so large that it will surpass `conn.limit(Limit::SQLITE_LIMIT_VARIABLE_NUMBER)`), chunking if too large. (Note that the limits api requires duckdb to have the “limits” feature).
  * `repeat_vars` can be implemented in a way that avoids needing to allocate a String.
  * Etc…


This complexity reflects the fact that `ParamsFromIter` is mainly intended for advanced use cases — most of the time you should know how many parameters you have statically (and if you don’t, you’re either doing something tricky, or should take a moment to think about the design).
```
Tokens:
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