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Merged
merged 8 commits into from
May 3, 2023
Merged

Add postgreSql character length functions #4121

merged 8 commits into from
May 3, 2023

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griffio
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@griffio griffio commented Apr 30, 2023

Add postgreSql character length functions
Add fixture test for use with constraint checks
Add integration test for use with client

Returns number of characters in the string or will return NULL if expression is NULL.

PostgreSQL supports Ansi CHAR_LENGTH, CHARACTER_LENGTH.
It also supports LENGTH, which is a PostgreSQL alias for CHAR_LENGTH.

  • length ( In MySql the length function is in bytes )
  • char_length
  • character_length

Multibyte characters count as a single character, not as bytes.

Examples

char_length ( text ) -> integer
char_length( 'jose' ) -> 4
char_length( '海豚' ) -> 2
char_length( NULL ) -> NULL

TODO

Add to MySql

❓ One question for the reviewer -- how to make the PostgreSqlTypeResolver.kt so that the char functions will type check string expressions and fail if passed a numeric?
e.g error function character_length(integer) does not exist

griffio added 6 commits May 1, 2023 19:00
@griffio
Add Integration test for PostgreSql Dialect length function
bee1060 
Test for length function can be executed standalone.

Test for Nullable type support is generated
@griffio
Add Character length functions for PostgreSql Dialect
df49812 
Returns number of characters in the string or will return NULL if expression is NULL.
In PostgreSql the following are synonymous and are Ansi Sql supported.
length ( In MySql the length function is in bytes )
char_length
character_length

char_length is ANSI SQL Standard and the explicitly named character_length,
as multibyte character counts as a single character not as bytes.

Examples

char_length ( text ) -> integer
char_length('jose') -> 4
char_length('海豚') -> 2
char_length(NULL) -> NULL
@griffio
Add Integration test fixture
31b16df
@griffio
Add test fixture for PostgreSql length function
d840ac4 
Support for all character length functions can be used in check constraint.
@griffio
Remove repetitive declaratiion
a3bc525
@griffio
Fix failing test
8ad37f7 
lowercase to compile - not sure if this should matter
@griffio griffio force-pushed the add-postgresql-length-functions branch from 54494fd to 8ad37f7 Compare May 1, 2023 18:00
@hfhbd
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hfhbd commented May 1, 2023 •
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AFAIK there is no sql type checker. While the compiler is able to get the expected Kotlin type, eg for SELECT length(?) to specify the Kotlin parameter (here String), there is no check, if the actual SQL function could handle this SQL type, like: SELECT length(42). And I don't think, there will be a SQL type checker in the future.

hfhbd
hfhbd previously approved these changes May 1, 2023
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Thanks!
Let's add MySql (and other dialects) in another PR.

@griffio
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griffio commented May 3, 2023

Ok. To try and understand further - using a bind variable - would it be expected for the SqlFunctionExpr to generate code to express e.g string->int ?

Would this work if the bind parameter is not related to a SqlColumn?

Given

selectLength:
  SELECT length(?);

val length = queries.selectLength("abc").executeAsOne()

results in mismatch: inferred type is String but Long? was expected

Maybe this is not supported

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hfhbd commented May 3, 2023

Yes, this should work! Could you add it as a test? I I will take a look later.

@hfhbd hfhbd self-requested a review May 3, 2023 12:27
@hfhbd hfhbd dismissed their stale review May 3, 2023 12:27

Found bug

@griffio
Length Function test
04ad12f 
Shows the error

Type mismatch: inferred type is String but Int? was expected
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griffio commented May 3, 2023

@hfhbd Thanks - Added failing test here 04ad12f

This problem already existed with calling functions

Type mismatch: inferred type is String but Int? was expected

Maybe it's related to this https://github.com/cashapp/sqldelight/pull/3431/files
Can only infer the same type? 🤔

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hfhbd commented May 3, 2023 •
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Thanks.
I think, there is a bigger root cause: we currently don't really have a good representation of a function, including the typed parameters. At the moment, we only specify the return type. The added Kotlin parameter type inference needs other typed sql parameters. In the past, to specify the kotlin type, you need to use a CAST. Ideally, we need a better function representation to specify the type of the parameters.

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hfhbd commented May 3, 2023

I was just about to ask to revert the test.
I am fine with merging this.

Rewriting the function implementation is another issue and properly won't make it into 2.0.

@hfhbd hfhbd merged commit 32d6c51 into sqldelight:master May 3, 2023
@griffio griffio deleted the add-postgresql-length-functions branch May 4, 2023 08:15
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