ClickHouse/docs/reference/settings/session-settings/function.mdx

---
title: 'function_* session settings'
sidebarTitle: 'function_*'
toc_max_heading_level: 2
description: 'ClickHouse session settings in the function_* generated group.'
doc_type: 'reference'
---

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import SettingsInfoBlock from "/snippets/components/SettingsInfoBlock/SettingsInfoBlock.jsx";
import { VersionHistory } from "/snippets/components/VersionHistory/VersionHistory.jsx";

These settings are available in [system.settings](/reference/system-tables/settings) and are autogenerated from [source](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).

## function_base58_max_input_size {#function_base58_max_input_size}

<SettingsInfoBlock type="UInt64" default_value="10000" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.6"},{"label": "10000"},{"label": "New setting that limits the input size of `base58Encode`, `base58Decode` and `tryBase58Decode` (whose conversion is quadratic in the input length) to 10 KB by default. The compatibility value `0` disables the limit, restoring the previous behavior of accepting arbitrarily large inputs."}]}]}/>

Maximum size, in bytes, of a single input value for the functions `base58Encode`, `base58Decode` and `tryBase58Decode`. The generic `base58` conversion is quadratic in the input length, so a single large value can run for a very long time. `base58` is meant for short data (keys, hashes, addresses), so the default of 10 KB is a generous safety threshold. `base58Encode` and `base58Decode` throw `TOO_LARGE_STRING_SIZE` for larger inputs, while `tryBase58Decode` returns an empty string. A value of `0` disables the limit (the behavior before this setting was introduced). The linear `base32` and `base64` functions are unaffected.

## function_date_trunc_return_type_behavior {#function_date_trunc_return_type_behavior}

<SettingsInfoBlock type="UInt64" default_value="0" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "25.7"},{"label": "0"},{"label": "Add new setting to preserve old behaviour of dateTrunc function"}]}, {"id": "row-2","items": [{"label": "25.4"},{"label": "0"},{"label": "Change the result type for dateTrunc function for DateTime64\/Date32 arguments to DateTime64\/Date32 regardless of time unit to get correct result for negative values"}]}]}/>

Allows to change the behaviour of the result type of `dateTrunc` function.

Possible values:

- 0 - When the second argument is `DateTime64/Date32` the return type will be `DateTime64/Date32` regardless of the time unit in the first argument.
- 1 - For `Date32` the result is always `Date`. For `DateTime64` the result is `DateTime` for time units `second` and higher.

## function_locate_has_mysql_compatible_argument_order {#function_locate_has_mysql_compatible_argument_order}

<SettingsInfoBlock type="Bool" default_value="1" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "24.3"},{"label": "1"},{"label": "Increase compatibility with MySQL's locate function."}]}]}/>

Controls the order of arguments in function [locate](/reference/functions/regular-functions/string-search-functions#locate).

Possible values:

- 0 — Function `locate` accepts arguments `(haystack, needle[, start_pos])`.
- 1 — Function `locate` accepts arguments `(needle, haystack, [, start_pos])` (MySQL-compatible behavior)

## function_range_max_elements_in_block {#function_range_max_elements_in_block}

<SettingsInfoBlock type="UInt64" default_value="500000000" />

Sets the safety threshold for data volume generated by functions [range](/reference/functions/regular-functions/array-functions#range),
[arrayPermutations](/reference/functions/regular-functions/array-functions#arrayPermutations),
[arrayPartialPermutations](/reference/functions/regular-functions/array-functions#arrayPartialPermutations),
[arrayCombinations](/reference/functions/regular-functions/array-functions#arrayCombinations),
[timeSeriesRange](/reference/functions/regular-functions/time-series-functions#timeSeriesRange),
and [timeSeriesFromGrid](/reference/functions/regular-functions/time-series-functions#timeSeriesFromGrid).
Defines the maximum number of values generated by functions per block of data (sum of array sizes for every row in a block).
For the combinatorics functions, which return `Array(Array(T))`, every generated inner array counts as its size plus one, so zero-length results still consume the limit.

Possible values:

- Positive integer.

**See Also**

- [`max_block_size`](/reference/settings/session-settings/max#max_block_size)
- [`min_insert_block_size_rows`](/reference/settings/session-settings/min-insert#min_insert_block_size_rows)

## function_sleep_max_microseconds_per_block {#function_sleep_max_microseconds_per_block}

<SettingsInfoBlock type="UInt64" default_value="3000000" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "23.7"},{"label": "3000000"},{"label": "In previous versions, the maximum sleep time of 3 seconds was applied only for `sleep`, but not for `sleepEachRow` function. In the new version, we introduce this setting. If you set compatibility with the previous versions, we will disable the limit altogether."}]}]}/>

Maximum number of microseconds the function `sleep` is allowed to sleep for each block. If a user called it with a larger value, it throws an exception. It is a safety threshold.

## function_visible_width_behavior {#function_visible_width_behavior}

<SettingsInfoBlock type="UInt64" default_value="1" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "24.1"},{"label": "1"},{"label": "We changed the default behavior of `visibleWidth` to be more precise"}]}]}/>

The version of `visibleWidth` behavior. 0 - only count the number of code points; 1 - correctly count zero-width and combining characters, count full-width characters as two, estimate the tab width, count delete characters.

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