Add alternative syntax for extract, trim and substring. (#13143)

Author: Omega359

datafusion/functions/src/datetime/date_part.rs

@@ -255,6 +255,7 @@ fn get_date_part_doc() -> &'static Documentation {
                 "expression",
                 "Time expression to operate on. Can be a constant, column, or function.",
             )
+            .with_alternative_syntax("extract(field FROM source)")
             .build()
             .unwrap()
     })

datafusion/functions/src/string/btrim.rs

@@ -124,6 +124,8 @@ fn get_btrim_doc() -> &'static Documentation {
 ```"#)
             .with_standard_argument("str", Some("String"))
             .with_argument("trim_str", "String expression to operate on. Can be a constant, column, or function, and any combination of operators. _Default is whitespace characters._")
+            .with_alternative_syntax("trim(BOTH trim_str FROM str)")
+            .with_alternative_syntax("trim(trim_str FROM str)")
             .with_related_udf("ltrim")
             .with_related_udf("rtrim")
             .build()

datafusion/functions/src/string/ltrim.rs

@@ -124,6 +124,7 @@ fn get_ltrim_doc() -> &'static Documentation {
 ```"#)
             .with_standard_argument("str", Some("String"))
             .with_argument("trim_str", "String expression to trim from the beginning of the input string. Can be a constant, column, or function, and any combination of arithmetic operators. _Default is whitespace characters._")
+            .with_alternative_syntax("trim(LEADING trim_str FROM str)")
             .with_related_udf("btrim")
             .with_related_udf("rtrim")
             .build()

datafusion/functions/src/string/rtrim.rs

@@ -124,6 +124,7 @@ fn get_rtrim_doc() -> &'static Documentation {
 ```"#)
             .with_standard_argument("str", Some("String"))
             .with_argument("trim_str", "String expression to trim from the end of the input string. Can be a constant, column, or function, and any combination of arithmetic operators. _Default is whitespace characters._")
+            .with_alternative_syntax("trim(TRAILING trim_str FROM str)")
             .with_related_udf("btrim")
             .with_related_udf("ltrim")
             .build()

datafusion/functions/src/unicode/substr.rs

@@ -173,6 +173,7 @@ fn get_substr_doc() -> &'static Documentation {
             .with_standard_argument("str", Some("String"))
             .with_argument("start_pos", "Character position to start the substring at. The first character in the string has a position of 1.")
             .with_argument("length", "Number of characters to extract. If not specified, returns the rest of the string after the start position.")
+            .with_alternative_syntax("substring(str from start_pos for length)")
             .build()
             .unwrap()
     })

docs/source/user-guide/sql/scalar_functions_new.md

@@ -808,6 +808,16 @@ btrim(str[, trim_str])
 +-------------------------------------------+
 ```
 
+#### Alternative Syntax
+
+```sql
+trim(BOTH trim_str FROM str)
+```
+
+```sql
+trim(trim_str FROM str)
+```
+
 #### Aliases
 
 - trim
@@ -1191,6 +1201,12 @@ ltrim(str[, trim_str])
 +-------------------------------------------+
 ```
 
+#### Alternative Syntax
+
+```sql
+trim(LEADING trim_str FROM str)
+```
+
 **Related functions**:
 
 - [btrim](#btrim)
@@ -1387,6 +1403,12 @@ rtrim(str[, trim_str])
 +-------------------------------------------+
 ```
 
+#### Alternative Syntax
+
+```sql
+trim(TRAILING trim_str FROM str)
+```
+
 **Related functions**:
 
 - [btrim](#btrim)
@@ -1501,6 +1523,12 @@ substr(str, start_pos[, length])
 +----------------------------------------------+
 ```
 
+#### Alternative Syntax
+
+```sql
+substring(str from start_pos for length)
+```
+
 #### Aliases
 
 - substring
@@ -1965,6 +1993,12 @@ date_part(part, expression)
 
 - **expression**: Time expression to operate on. Can be a constant, column, or function.
 
+#### Alternative Syntax
+
+```sql
+extract(field FROM source)
+```
+
 #### Aliases
 
 - datepart