#28643: Complete the ORM Function Library
-------------------------------------+-------------------------------------
     Reporter:  Matthew Pava         |                    Owner:  JunyiJ
         Type:  New feature          |                   Status:  assigned
    Component:  Database layer       |                  Version:  master
  (models, ORM)                      |
     Severity:  Normal               |               Resolution:
     Keywords:                       |             Triage Stage:  Accepted
    Has patch:  1                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------
Description changed by Mads Jensen:

Old description:

> I was surprised to learn that we didn't have a StrIndex function until
> version 2, and yet we had Substr since at least version 1.8.  I wonder
> how users were using Substr without also finding a use for StrIndex this
> whole time.  Anyway, since we seem to be adding these functions one at a
> time, why don't we work on trying to get the built-ins implemented in one
> sweep instead?
>
> We may even want to split the documentation page
> (https://docs.djangoproject.com/en/dev/ref/models/database-functions/)
> into further categories with String functions and Numeric functions.
>
> This is just a sample checklist, with corresponding attributes to which
> backend has them available.
>
> ||||||||||||||= **Comparison** =||
> ||**Name**||**Description**||**PostgreSQL**||**Oracle**||**MySQL**||**SQLite**||**PR**||
> ||NULLIF()||Returns NULL if the first argument equals the
> second.||X||X||X||X||-||
> ||||||||||||||= **Math** =||
> ||**Name**||**Description**||**PostgreSQL**||**Oracle**||**MySQL**||**SQLite**||**PR**||
> ||ABS()||Returns the absolute value.||X||X||X||X||-||
> ||ACOS()||Returns the arccosine.||X||X||X||-||-||
> ||ASIN()||Returns the arcsine.||X||X||X||-||-||
> ||ATAN()||Returns the arctangent.||X||X||X||-||-||
> ||ATAN2()||Returns the arctangent of the two variables passed to
> it.||X||X||X||-||-||
> ||CEILING()||Returns the smallest integer value that is not less than a
> numeric expression||X||as CEIL()||X||-||-||
> ||COS()||Returns the cosine expressed in radians.||X||X||X||-||-||
> ||COT()||Returns the cotangent.||X||X||X||-||-||
> ||DEGREES()||Returns a numeric expression converted from radians to
> degrees.||X||X||X||-||-||
> ||EXP()||Returns the base of the natural logarithm (e) raised to the
> power of a numeric expression.||X||X||X||-||-||
> ||FLOOR()||Returns the largest integer value that is not greater than a
> numeric expression.||X||X||X||-||-||
> ||LOG()||Returns the natural logarithm of a numeric
> expression.||X||X||X||-||-||
> ||MOD()||Returns the remainder of one expression by diving by another
> expression.||X||X||X||-||-||
> ||PI()||Returns the value of pi||X||-||X||-||-||
> ||POWER()||Returns the value of one expression raised to the power of
> another expression||X||X||X||-||-||
> ||RADIANS()||Returns the value of an expression converted from degrees to
> radians.||X||X||X||-||-||
> ||ROUND()||Returns a numeric expression rounded to an integer.\\Can be
> used to round an expression to a number of decimal
> points||X||X||X||X||-||
> ||SIN()||Returns the sine given in radians.||X||X||X||-||-||
> ||SQRT()||Returns the square root.||X||X||X||-||-||
> ||TAN()||Returns the tangent expressed in radians.||X||X||X||-||-||
> ||||||||||||||= **Text** =||
> ||**Name**||**Description**||**PostgreSQL**||**Oracle**||**MySQL**||**SQLite**||**PR**||
> ||ASCII()||Returns numeric value of left-most character||X||X||X||as
> UNICODE()||-||
> ||CHR()||Character with the given code||X||X||as CHAR()||as CHAR()||-||
> ||LEFT()||Returns the leftmost number of characters as
> specified||X||-||X||-||-||
> ||LPAD()||Returns the string argument, left-padded with the specified
> string||X||X||X||-||-||
> ||LTRIM()||Removes leading
> spaces||X||X||X||X||[https://github.com/django/django/pull/9220 9220]||
> ||MD5()||Calculates the MD5 hash of string, returning the result in
> hexadecimal||X||-||-||-||-||
> ||REPEAT()||Repeats a string the specified number of
> times||X||-||X||-||-||
> ||REPLACE()||Replaces occurrences of a specified string||X||X||X||X||-||
> ||REVERSE()||Reverse the characters in a string||X||-||X||-||-||
> ||RIGHT()||Returns the specified rightmost number of
> characters||X||-||X||-||-||
> ||RPAD()||Appends string the specified number of times||X||X||X||-||-||
> ||RTRIM()||Removes trailing
> spaces||X||X||X||X||[https://github.com/django/django/pull/9220 9220]||
> ||TRIM()||Removes leading and trailing
> spaces||X||X||X||X||[https://github.com/django/django/pull/9220 9220]||

New description:

 I was surprised to learn that we didn't have a StrIndex function until
 version 2, and yet we had Substr since at least version 1.8.  I wonder how
 users were using Substr without also finding a use for StrIndex this whole
 time.  Anyway, since we seem to be adding these functions one at a time,
 why don't we work on trying to get the built-ins implemented in one sweep
 instead?

 We may even want to split the documentation page
 (https://docs.djangoproject.com/en/dev/ref/models/database-functions/)
 into further categories with String functions and Numeric functions.

 This is just a sample checklist, with corresponding attributes to which
 backend has them available.

 ||||||||||||||= **Comparison** =||
 
||**Name**||**Description**||**PostgreSQL**||**Oracle**||**MySQL**||**SQLite**||**PR**||
 ||NULLIF()||Returns NULL if the first argument equals the
 second.||X||X||X||X||-||
 ||||||||||||||= **Math** =||
 
||**Name**||**Description**||**PostgreSQL**||**Oracle**||**MySQL**||**SQLite**||**PR**||
 ||ABS()||Returns the absolute value.||X||X||X||X||-||
 ||ACOS()||Returns the arccosine.||X||X||X||-||-||
 ||ASIN()||Returns the arcsine.||X||X||X||-||-||
 ||ATAN()||Returns the arctangent.||X||X||X||-||-||
 ||ATAN2()||Returns the arctangent of the two variables passed to
 it.||X||X||X||-||-||
 ||CEILING()||Returns the smallest integer value that is not less than a
 numeric expression||X||as CEIL()||X||-||-||
 ||COS()||Returns the cosine expressed in radians.||X||X||X||-||-||
 ||COT()||Returns the cotangent.||X||X||X||-||-||
 ||DEGREES()||Returns a numeric expression converted from radians to
 degrees.||X||X||X||-||-||
 ||EXP()||Returns the base of the natural logarithm (e) raised to the power
 of a numeric expression.||X||X||X||-||-||
 ||FLOOR()||Returns the largest integer value that is not greater than a
 numeric expression.||X||X||X||-||-||
 ||LOG()||Returns the natural logarithm of a numeric
 expression.||X||X||X||-||-||
 ||MOD()||Returns the remainder of one expression by diving by another
 expression.||X||X||X||-||-||
 ||PI()||Returns the value of pi||X||-||X||-||-||
 ||POWER()||Returns the value of one expression raised to the power of
 another expression||X||X||X||-||-||
 ||RADIANS()||Returns the value of an expression converted from degrees to
 radians.||X||X||X||-||-||
 ||ROUND()||Returns a numeric expression rounded to an integer.\\Can be
 used to round an expression to a number of decimal points||X||X||X||X||-||
 ||SIN()||Returns the sine given in radians.||X||X||X||-||-||
 ||SQRT()||Returns the square root.||X||X||X||-||-||
 ||TAN()||Returns the tangent expressed in radians.||X||X||X||-||-||
 ||||||||||||||= **Text** =||
 
||**Name**||**Description**||**PostgreSQL**||**Oracle**||**MySQL**||**SQLite**||**PR**||
 ||ASCII()||Returns numeric value of left-most character||X||X||X||as
 UNICODE()||-||
 ||CHR()||Character with the given code||X||X||as CHAR()||as CHAR()||-||
 ||LEFT()||Returns the leftmost number of characters as
 specified||X||-||X||-||-||
 ||LPAD()||Returns the string argument, left-padded with the specified
 string||X||X||X||-||-||
 ||LTRIM()||Removes leading
 spaces||X||X||X||X||[https://github.com/django/django/pull/9220 9220]||
 ||MD5()||Calculates the MD5 hash of string, returning the result in
 hexadecimal||X||-||-||-||-||
 ||REPEAT()||Repeats a string the specified number of
 times||X||-||X||-||-||
 ||REPLACE()||Replaces occurrences of a specified
 string||X||X||X||X||[https://github.com/django/django/pull/9539 9539]||
 ||REVERSE()||Reverse the characters in a string||X||-||X||-||-||
 ||RIGHT()||Returns the specified rightmost number of
 characters||X||-||X||-||-||
 ||RPAD()||Appends string the specified number of times||X||X||X||-||-||
 ||RTRIM()||Removes trailing
 spaces||X||X||X||X||[https://github.com/django/django/pull/9220 9220]||
 ||TRIM()||Removes leading and trailing
 spaces||X||X||X||X||[https://github.com/django/django/pull/9220 9220]||

--

-- 
Ticket URL: <https://code.djangoproject.com/ticket/28643#comment:25>
Django <https://code.djangoproject.com/>
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