Merge pull request #3957 from Blargian/autogenerate_conditional

autogenerate conditional functions

Author: Blargian

contribute/autogenerated-documentation-from-source.md

@@ -1,15 +1,18 @@
 # Generating documentation from source code
 
 A [script in our docs repo](https://github.com/ClickHouse/clickhouse-docs/blob/main/scripts/settings/autogenerate-settings.sh) 
-extracts setting names, descriptions, default values, etc. from ClickHouse's source code.
+is used to run SQL queries which generate markdown documentation from the system tables in ClickHouse and insert it 
+into the appropriate pages before build time of the docs.
 
 ## Session settings
 
 Documentation for session settings is autogenerated from source file [`src/Core/Settings.cpp`](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).
+[SQL](../scripts/settings/session-settings.sql)
 
 ## Format settings
 
 Documentation for session settings is autogenerated from source file [`src/Core/FormatFactorySettings.h`](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/FormatFactorySettings.h).
+[SQL](../scripts/settings/format-settings.sql)
 
 ## Server settings
 
@@ -43,14 +46,33 @@ If it is, then please edit the setting description in the source code documentat
 in [`ServerSettings.cpp`](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/ServerSettings.cpp) 
 or else edit `_server_settings_outside_source.md`.**
 
+[SQL](../scripts/settings/global-server-settings.sql)
+
 ## MergeTree settings
 
 Documentation for MergeTree settings is autogenerated from [MergeTreeSettings.cpp](https://github.com/ClickHouse/ClickHouse/blob/master/src/Storages/MergeTree/MergeTreeSettings.cpp)
 
+[SQL](../scripts/settings/mergetree-settings.sql)
+
 ## System tables
 
-TO DO. ETA April.
+TO DO
 
 ## Functions
 
-TO DO. ETA April/May.
+Documentation for functions is autogenerated from the documentation in system tables (`system.functions`) which is 
+registered along with the function registration in the C++ code.
+
+To add a new page:
+- add SQL to generate the markdown from system tables
+- update `autogenerate-settings.sh` in the section which specifies which markdown file contents to
+  copy to which file in between the `<!--AUTOGENERATED_START-->` and `<!--AUTOGENERATED_END-->`
+
+The following pages are autogenerated from the source code for functions:
+- [Arithmetic](/sql-reference/functions/arithmetic-functions) ([SQL](../scripts/settings/arithmetic-functions.sql))
+- [Arrays](/sql-reference/functions/array-functions) ([SQL](../scripts/settings/array-functions.sql))
+- [Bit](/sql-reference/functions/bit-functions) ([SQL](../scripts/settings/bit-functions.sql))
+- [Bitmap](/sql-reference/functions/bitmap-functions) ([SQL](../scripts/settings/bitmap-functions.sql))
+- [Comparison](/sql-reference/functions/comparison-functions) ([SQL](../scripts/settings/comparison-functions.sql))
+- [Conditional](/sql-reference/functions/conditional-functions) ([SQL](../scripts/settings/conditional-functions.sql))
+

scripts/settings/autogenerate-settings.sh

@@ -318,6 +318,7 @@ insert_src_files=(
   "bit-functions.md"
   "bitmap-functions.md"
   "comparison-functions.md"
+  "conditional-functions.md"
 )
 insert_dest_files=(
     "docs/about-us/beta-and-experimental-features.md"
@@ -326,6 +327,7 @@ insert_dest_files=(
     "docs/sql-reference/functions/bit-functions.md"
     "docs/sql-reference/functions/bitmap-functions.md"
     "docs/sql-reference/functions/comparison-functions.md"
+    "docs/sql-reference/functions/conditional-functions.md"
 )
 echo "[$SCRIPT_NAME] Inserting generated markdown content between <!-- AUTOGENERATED_START --> <!-- AUTOGENERATED_END --> tags"
 for i in "${!insert_src_files[@]}"; do

scripts/settings/conditional-functions.sql

@@ -0,0 +1,22 @@
+WITH conditional_functions AS (
+    SELECT
+        name,
+        introduced_in,
+        syntax,
+        arguments,
+        returned_value,
+        examples
+    FROM system.functions WHERE categories='Conditional' ORDER BY name ASC
+)
+SELECT
+    format(
+            '{}{}{}{}{}{}',
+            '## ' || name || ' ' || printf('{#%s}', name) || '\n\n',
+            'Introduced in: v'||introduced_in||'\n\n',
+            '**Syntax**\n\n'||printf('```sql\n%s\n```', syntax)||'\n\n',
+            if(empty(arguments), '**Arguments**\n\n- None.\n', '**Arguments**\n\n'||arguments||'\n'),
+            '**Returned value**\n\n'||trim(returned_value)||'\n\n',
+            '**Examples**\n\n'||examples||'\n'
+    )
+FROM conditional_functions
+    INTO OUTFILE 'conditional-functions.md' TRUNCATE FORMAT LineAsString