https://github.com/d6y/delete-by-count

Investigation of delete behaviour
https://github.com/d6y/delete-by-count

Last synced: about 1 month ago
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Investigation of delete behaviour

• Host: GitHub
• URL: https://github.com/d6y/delete-by-count
• Owner: d6y
• Created: 2015-11-26T10:42:24.000Z (about 9 years ago)
• Default Branch: master
• Last Pushed: 2015-11-26T10:44:08.000Z (about 9 years ago)
• Last Synced: 2023-03-10T19:08:48.035Z (almost 2 years ago)
• Language: Scala
• Size: 2.93 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Possible delete regression in 3.1?

The following query...

```scala

// Delete all messages that have a duplicate (leaving zero rows with that content)

val zap =

  messages.filter { msg =>

    messages.filter(_.content === msg.content).size > 1

  }.delete

```

...produces different results with Slick 3.0 and 3.1

In a table containing the rows:

- Hello

- Hello

- Yo!

...I would expect the query to remove the first two rows.

- Under 3.0 it removes 2 rows (yay!)

- Under 3.1 it removes 3 rows (huh?).

This is with h2.

The queries are (3.0 then 3.1):

```sql

delete from "message" where (select count(1) from "message" x2 where x2."content" = "message"."content") > 1

delete from "message" where (select count(1) from "message" where "content" = "message"."content") > 1

```

Note the difference in the `x2` prefix.

## Steps to reproduce

1. Set the _build.sbt_ Slick version to 3.0 or 3.1

2. Exec `run` in sbt and observe the results below.

##  Results running with Slick 3.0

```

[info] Compiling 1 Scala source to /Users/richard/Developer/books/delete-by-count/target/scala-2.11/classes...

[info] Running Example

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: create table "message" ("content" VARCHAR NOT NULL)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: insert into "message" ("content")  values (?)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: insert into "message" ("content")  values (?)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: insert into "message" ("content")  values (?)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: delete from "message" where (select count(1) from "message" x2 where x2."content" = "message"."content") > 1

2

```

##  Results running with Slick 3.1

```

[info] Running Example

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: create table "message" ("content" VARCHAR NOT NULL)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: insert into "message" ("content")  values (?)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: insert into "message" ("content")  values (?)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: insert into "message" ("content")  values (?)

DEBUG slick.jdbc.JdbcBackend.statement - Preparing statement: delete from "message" where (select count(1) from "message" where "content" = "message"."content") > 1

3

```