Multi_insert returns more results than expected in some specific conditions

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#384 5 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
mysql, ruby, sql
Domain
databases

Research direction

Start by tracing relation.multi_insert and the relation.primary_key lookup described in the issue, then reproduce the behavior with the provided composite-key MySQL schema and create command. Done means the command returns only the inserted rows, or no rows if that behavior is chosen, rather than every row in the table.

Written by the indexing model from the issue text.

Description

bug

Describe the bug

When using mysql2 as the underlying driver, dealing with a table that has a multi-column primary key, multi_insert tries to get back the primary key from the inserts. However, since this is a multi-column PK, LAST_INSERT_ID() has 0, so relation.multi_insert will give back an array of 0.
multi_insert will in turn, try to query the relation with the primary keys it got back. It uses relation.primary_key for this, which will return as far as I can understand the first field of the PK. If the PK has a varchar as the first field, this will result in a query such as SELECT * FROM relation where varchar_field in (0, 0, 0...), which in mysql will return every field in the table.

To Reproduce

Create a table which contain more than one column as primary key, such as:

CREATE TABLE `my_table` (
  `my_field1` varchar(255) NOT NULL,
  `my_field2` varchar(255) NOT NULL,
  PRIMARY KEY (`my_field1`, `my_field2`)
)

Insert random data in the created able.

Try to insert more than one value in this table using something like so:

new_values = [{my_field1: "abc", my_field2: "cde"}, {my_field1: "gde", my_field2: "zyx"}]
create_cmd = my_table.command(:create, result: :many)
d = create_cmd.call(new_values)

d will contain all rows in the table, instead of only the two inserted ones.

Expected behavior

Only the two values are returned (or optionally, no values at all)

Your environment

  • Affects my production application: No, we rolled back our change and we're going straight to the db.
  • Ruby version: 2.6
  • OS: Linux
  • Rom-sql 3.1.0
  • Rom-core 5.1.2
Dominant language
Ruby
Stars
220
Forks
97
No merged PRs in 30d

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