---
layout: docu
redirect_from:
- /docs/api/c/table_functions
- /docs/api/c/table_functions/
- /docs/clients/c/table_functions
title: Table Functions
---

<!-- markdownlint-disable MD001 -->

The table function API can be used to define a table function that can then be called from within DuckDB in the `FROM` clause of a query.

## API Reference Overview

<!-- This section is generated by scripts/generate_c_api_docs.py -->

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">duckdb_table_function</span> <a href="#duckdb_create_table_function"><span class="nf">duckdb_create_table_function</span></a>();
<span class="kt">void</span> <a href="#duckdb_destroy_table_function"><span class="nf">duckdb_destroy_table_function</span></a>(<span class="kt">duckdb_table_function</span> *<span class="nv">table_function</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_set_name"><span class="nf">duckdb_table_function_set_name</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_add_parameter"><span class="nf">duckdb_table_function_add_parameter</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="kt">duckdb_logical_type</span> <span class="nv">type</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_add_named_parameter"><span class="nf">duckdb_table_function_add_named_parameter</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name</span>, <span class="kt">duckdb_logical_type</span> <span class="nv">type</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_set_extra_info"><span class="nf">duckdb_table_function_set_extra_info</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="kt">void</span> *<span class="nv">extra_info</span>, <span class="nv">duckdb_delete_callback_t</span> <span class="nv">destroy</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_set_bind"><span class="nf">duckdb_table_function_set_bind</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="nv">duckdb_table_function_bind_t</span> <span class="nv">bind</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_set_init"><span class="nf">duckdb_table_function_set_init</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="nv">duckdb_table_function_init_t</span> <span class="nv">init</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_set_local_init"><span class="nf">duckdb_table_function_set_local_init</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="nv">duckdb_table_function_init_t</span> <span class="nv">init</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_set_function"><span class="nf">duckdb_table_function_set_function</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="nv">duckdb_table_function_t</span> <span class="nv">function</span>);
<span class="kt">void</span> <a href="#duckdb_table_function_supports_projection_pushdown"><span class="nf">duckdb_table_function_supports_projection_pushdown</span></a>(<span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>, <span class="kt">bool</span> <span class="nv">pushdown</span>);
<span class="kt">duckdb_state</span> <a href="#duckdb_register_table_function"><span class="nf">duckdb_register_table_function</span></a>(<span class="kt">duckdb_connection</span> <span class="nv">con</span>, <span class="kt">duckdb_table_function</span> <span class="nv">function</span>);
</code></pre></div></div>

### Table Function Bind

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<a href="#duckdb_bind_get_extra_info"><span class="nf">duckdb_bind_get_extra_info</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>);
<span class="kt">void</span> <a href="#duckdb_bind_add_result_column"><span class="nf">duckdb_bind_add_result_column</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>, <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name</span>, <span class="kt">duckdb_logical_type</span> <span class="nv">type</span>);
<span class="kt">idx_t</span> <a href="#duckdb_bind_get_parameter_count"><span class="nf">duckdb_bind_get_parameter_count</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>);
<span class="kt">duckdb_value</span> <a href="#duckdb_bind_get_parameter"><span class="nf">duckdb_bind_get_parameter</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>, <span class="kt">idx_t</span> <span class="nv">index</span>);
<span class="kt">duckdb_value</span> <a href="#duckdb_bind_get_named_parameter"><span class="nf">duckdb_bind_get_named_parameter</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>, <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name</span>);
<span class="kt">void</span> <a href="#duckdb_bind_set_bind_data"><span class="nf">duckdb_bind_set_bind_data</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>, <span class="kt">void</span> *<span class="nv">bind_data</span>, <span class="nv">duckdb_delete_callback_t</span> <span class="nv">destroy</span>);
<span class="kt">void</span> <a href="#duckdb_bind_set_cardinality"><span class="nf">duckdb_bind_set_cardinality</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>, <span class="kt">idx_t</span> <span class="nv">cardinality</span>, <span class="kt">bool</span> <span class="nv">is_exact</span>);
<span class="kt">void</span> <a href="#duckdb_bind_set_error"><span class="nf">duckdb_bind_set_error</span></a>(<span class="kt">duckdb_bind_info</span> <span class="nv">info</span>, <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">error</span>);
</code></pre></div></div>

### Table Function Init

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<a href="#duckdb_init_get_extra_info"><span class="nf">duckdb_init_get_extra_info</span></a>(<span class="kt">duckdb_init_info</span> <span class="nv">info</span>);
<span class="kt">void</span> *<a href="#duckdb_init_get_bind_data"><span class="nf">duckdb_init_get_bind_data</span></a>(<span class="kt">duckdb_init_info</span> <span class="nv">info</span>);
<span class="kt">void</span> <a href="#duckdb_init_set_init_data"><span class="nf">duckdb_init_set_init_data</span></a>(<span class="kt">duckdb_init_info</span> <span class="nv">info</span>, <span class="kt">void</span> *<span class="nv">init_data</span>, <span class="nv">duckdb_delete_callback_t</span> <span class="nv">destroy</span>);
<span class="kt">idx_t</span> <a href="#duckdb_init_get_column_count"><span class="nf">duckdb_init_get_column_count</span></a>(<span class="kt">duckdb_init_info</span> <span class="nv">info</span>);
<span class="kt">idx_t</span> <a href="#duckdb_init_get_column_index"><span class="nf">duckdb_init_get_column_index</span></a>(<span class="kt">duckdb_init_info</span> <span class="nv">info</span>, <span class="kt">idx_t</span> <span class="nv">column_index</span>);
<span class="kt">void</span> <a href="#duckdb_init_set_max_threads"><span class="nf">duckdb_init_set_max_threads</span></a>(<span class="kt">duckdb_init_info</span> <span class="nv">info</span>, <span class="kt">idx_t</span> <span class="nv">max_threads</span>);
<span class="kt">void</span> <a href="#duckdb_init_set_error"><span class="nf">duckdb_init_set_error</span></a>(<span class="kt">duckdb_init_info</span> <span class="nv">info</span>, <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">error</span>);
</code></pre></div></div>

### Table Function

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<a href="#duckdb_function_get_extra_info"><span class="nf">duckdb_function_get_extra_info</span></a>(<span class="kt">duckdb_function_info</span> <span class="nv">info</span>);
<span class="kt">void</span> *<a href="#duckdb_function_get_bind_data"><span class="nf">duckdb_function_get_bind_data</span></a>(<span class="kt">duckdb_function_info</span> <span class="nv">info</span>);
<span class="kt">void</span> *<a href="#duckdb_function_get_init_data"><span class="nf">duckdb_function_get_init_data</span></a>(<span class="kt">duckdb_function_info</span> <span class="nv">info</span>);
<span class="kt">void</span> *<a href="#duckdb_function_get_local_init_data"><span class="nf">duckdb_function_get_local_init_data</span></a>(<span class="kt">duckdb_function_info</span> <span class="nv">info</span>);
<span class="kt">void</span> <a href="#duckdb_function_set_error"><span class="nf">duckdb_function_set_error</span></a>(<span class="kt">duckdb_function_info</span> <span class="nv">info</span>, <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">error</span>);
</code></pre></div></div>

#### `duckdb_create_table_function`

Creates a new empty table function.

The return value should be destroyed with `duckdb_destroy_table_function`.


##### Return Value

The table function object.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">duckdb_table_function</span> <span class="nv">duckdb_create_table_function</span>(<span class="nv">
</span>  <span class="nv">
</span>);
</code></pre></div></div>
<br>

#### `duckdb_destroy_table_function`

Destroys the given table function object.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_destroy_table_function</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> *<span class="nv">table_function
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function to destroy

<br>

#### `duckdb_table_function_set_name`

Sets the name of the given table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_set_name</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function
* `name`: The name of the table function

<br>

#### `duckdb_table_function_add_parameter`

Adds a parameter to the table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_add_parameter</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="kt">duckdb_logical_type</span> <span class="nv">type
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function.
* `type`: The parameter type. Cannot contain INVALID.

<br>

#### `duckdb_table_function_add_named_parameter`

Adds a named parameter to the table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_add_named_parameter</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name</span>,<span class="nv">
</span>  <span class="kt">duckdb_logical_type</span> <span class="nv">type
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function.
* `name`: The parameter name.
* `type`: The parameter type. Cannot contain INVALID.

<br>

#### `duckdb_table_function_set_extra_info`

Assigns extra information to the table function that can be fetched during binding, etc.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_set_extra_info</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="kt">void</span> *<span class="nv">extra_info</span>,<span class="nv">
</span>  <span class="nv">duckdb_delete_callback_t</span> <span class="nv">destroy
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function
* `extra_info`: The extra information
* `destroy`: The callback that will be called to destroy the bind data (if any)

<br>

#### `duckdb_table_function_set_bind`

Sets the bind function of the table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_set_bind</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="nv">duckdb_table_function_bind_t</span> <span class="nv">bind
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function
* `bind`: The bind function

<br>

#### `duckdb_table_function_set_init`

Sets the init function of the table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_set_init</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="nv">duckdb_table_function_init_t</span> <span class="nv">init
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function
* `init`: The init function

<br>

#### `duckdb_table_function_set_local_init`

Sets the thread-local init function of the table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_set_local_init</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="nv">duckdb_table_function_init_t</span> <span class="nv">init
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function
* `init`: The init function

<br>

#### `duckdb_table_function_set_function`

Sets the main function of the table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_set_function</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="nv">duckdb_table_function_t</span> <span class="nv">function
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function
* `function`: The function

<br>

#### `duckdb_table_function_supports_projection_pushdown`

Sets whether or not the given table function supports projection pushdown.

If this is set to true, the system will provide a list of all required columns in the `init` stage through
the `duckdb_init_get_column_count` and `duckdb_init_get_column_index` functions.
If this is set to false (the default), the system will expect all columns to be projected.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_table_function_supports_projection_pushdown</span>(<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">table_function</span>,<span class="nv">
</span>  <span class="kt">bool</span> <span class="nv">pushdown
</span>);
</code></pre></div></div>

##### Parameters

* `table_function`: The table function
* `pushdown`: True if the table function supports projection pushdown, false otherwise.

<br>

#### `duckdb_register_table_function`

Register the table function object within the given connection.

The function requires at least a name, a bind function, an init function and a main function.

If the function is incomplete or a function with this name already exists DuckDBError is returned.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">duckdb_state</span> <span class="nv">duckdb_register_table_function</span>(<span class="nv">
</span>  <span class="kt">duckdb_connection</span> <span class="nv">con</span>,<span class="nv">
</span>  <span class="kt">duckdb_table_function</span> <span class="nv">function
</span>);
</code></pre></div></div>

##### Parameters

* `con`: The connection to register it in.
* `function`: The function pointer

##### Return Value

Whether or not the registration was successful.

<br>

#### `duckdb_bind_get_extra_info`

Retrieves the extra info of the function as set in `duckdb_table_function_set_extra_info`.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<span class="nv">duckdb_bind_get_extra_info</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The extra info

<br>

#### `duckdb_bind_add_result_column`

Adds a result column to the output of the table function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_bind_add_result_column</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name</span>,<span class="nv">
</span>  <span class="kt">duckdb_logical_type</span> <span class="nv">type
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The table function's bind info.
* `name`: The column name.
* `type`: The logical column type.

<br>

#### `duckdb_bind_get_parameter_count`

Retrieves the number of regular (non-named) parameters to the function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">idx_t</span> <span class="nv">duckdb_bind_get_parameter_count</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The number of parameters

<br>

#### `duckdb_bind_get_parameter`

Retrieves the parameter at the given index.

The result must be destroyed with `duckdb_destroy_value`.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">duckdb_value</span> <span class="nv">duckdb_bind_get_parameter</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">idx_t</span> <span class="nv">index
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `index`: The index of the parameter to get

##### Return Value

The value of the parameter. Must be destroyed with `duckdb_destroy_value`.

<br>

#### `duckdb_bind_get_named_parameter`

Retrieves a named parameter with the given name.

The result must be destroyed with `duckdb_destroy_value`.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">duckdb_value</span> <span class="nv">duckdb_bind_get_named_parameter</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">name
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `name`: The name of the parameter

##### Return Value

The value of the parameter. Must be destroyed with `duckdb_destroy_value`.

<br>

#### `duckdb_bind_set_bind_data`

Sets the user-provided bind data in the bind object. This object can be retrieved again during execution.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_bind_set_bind_data</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">void</span> *<span class="nv">bind_data</span>,<span class="nv">
</span>  <span class="nv">duckdb_delete_callback_t</span> <span class="nv">destroy
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `bind_data`: The bind data object.
* `destroy`: The callback that will be called to destroy the bind data (if any)

<br>

#### `duckdb_bind_set_cardinality`

Sets the cardinality estimate for the table function, used for optimization.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_bind_set_cardinality</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">idx_t</span> <span class="nv">cardinality</span>,<span class="nv">
</span>  <span class="kt">bool</span> <span class="nv">is_exact
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The bind data object.
* `is_exact`: Whether or not the cardinality estimate is exact, or an approximation

<br>

#### `duckdb_bind_set_error`

Report that an error has occurred while calling bind.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_bind_set_error</span>(<span class="nv">
</span>  <span class="kt">duckdb_bind_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">error
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `error`: The error message

<br>

#### `duckdb_init_get_extra_info`

Retrieves the extra info of the function as set in `duckdb_table_function_set_extra_info`.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<span class="nv">duckdb_init_get_extra_info</span>(<span class="nv">
</span>  <span class="kt">duckdb_init_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The extra info

<br>

#### `duckdb_init_get_bind_data`

Gets the bind data set by `duckdb_bind_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.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<span class="nv">duckdb_init_get_bind_data</span>(<span class="nv">
</span>  <span class="kt">duckdb_init_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The bind data object

<br>

#### `duckdb_init_set_init_data`

Sets the user-provided init data in the init object. This object can be retrieved again during execution.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_init_set_init_data</span>(<span class="nv">
</span>  <span class="kt">duckdb_init_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">void</span> *<span class="nv">init_data</span>,<span class="nv">
</span>  <span class="nv">duckdb_delete_callback_t</span> <span class="nv">destroy
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `init_data`: The init data object.
* `destroy`: The callback that will be called to destroy the init data (if any)

<br>

#### `duckdb_init_get_column_count`

Returns the number of projected columns.

This function must be used if projection pushdown is enabled to figure out which columns to emit.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">idx_t</span> <span class="nv">duckdb_init_get_column_count</span>(<span class="nv">
</span>  <span class="kt">duckdb_init_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The number of projected columns.

<br>

#### `duckdb_init_get_column_index`

Returns the column index of the projected column at the specified position.

This function must be used if projection pushdown is enabled to figure out which columns to emit.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">idx_t</span> <span class="nv">duckdb_init_get_column_index</span>(<span class="nv">
</span>  <span class="kt">duckdb_init_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">idx_t</span> <span class="nv">column_index
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `column_index`: The index at which to get the projected column index, from 0..duckdb_init_get_column_count(info)

##### Return Value

The column index of the projected column.

<br>

#### `duckdb_init_set_max_threads`

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

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_init_set_max_threads</span>(<span class="nv">
</span>  <span class="kt">duckdb_init_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">idx_t</span> <span class="nv">max_threads
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `max_threads`: The maximum amount of threads that can process this table function

<br>

#### `duckdb_init_set_error`

Report that an error has occurred while calling init.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_init_set_error</span>(<span class="nv">
</span>  <span class="kt">duckdb_init_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">error
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `error`: The error message

<br>

#### `duckdb_function_get_extra_info`

Retrieves the extra info of the function as set in `duckdb_table_function_set_extra_info`.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<span class="nv">duckdb_function_get_extra_info</span>(<span class="nv">
</span>  <span class="kt">duckdb_function_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The extra info

<br>

#### `duckdb_function_get_bind_data`

Gets the bind data set by `duckdb_bind_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.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<span class="nv">duckdb_function_get_bind_data</span>(<span class="nv">
</span>  <span class="kt">duckdb_function_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The bind data object

<br>

#### `duckdb_function_get_init_data`

Gets the init data set by `duckdb_init_set_init_data` during the init.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<span class="nv">duckdb_function_get_init_data</span>(<span class="nv">
</span>  <span class="kt">duckdb_function_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The init data object

<br>

#### `duckdb_function_get_local_init_data`

Gets the thread-local init data set by `duckdb_init_set_init_data` during the local_init.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> *<span class="nv">duckdb_function_get_local_init_data</span>(<span class="nv">
</span>  <span class="kt">duckdb_function_info</span> <span class="nv">info
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object

##### Return Value

The init data object

<br>

#### `duckdb_function_set_error`

Report that an error has occurred while executing the function.

##### Syntax

<div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="nv">duckdb_function_set_error</span>(<span class="nv">
</span>  <span class="kt">duckdb_function_info</span> <span class="nv">info</span>,<span class="nv">
</span>  <span class="kt">const</span> <span class="kt">char</span> *<span class="nv">error
</span>);
</code></pre></div></div>

##### Parameters

* `info`: The info object
* `error`: The error message

<br>