MDEV-31414: Implement optional lengths for string types by OsamaNabih · Pull Request #4551 · MariaDB/server

OsamaNabih · 2026-01-17T19:13:53Z

Jira: https://jira.mariadb.org/browse/MDEV-31414
Adding support for SQL standard 2023's T081: Optional string types maximum length

This PR allows the user to not specify a length for a VARCHAR field. We default to making the field a TEXT type.

CLAassistant · 2026-01-17T19:14:01Z

All committers have signed the CLA.

FooBarrior · 2026-01-17T22:27:14Z

Hi,

Is 16383 reported as the maximum due to collation choice?

That is a nice guess!

Our documentation claims it's 21,844 characters, though I think it's a bit outdated, since we support 4-byte encodings for some time. So yes, it's got to be UINT16_MAX/4 - header_length, where header_length is something like 3.

FooBarrior

We follow the TDD paradigm - every feature should be covered with tests (and every bugfix, if possible). Include both .test and .result files in the commit.

I'm fine with a hard constant of 16383 in scope of this small work, we can always extend it and make a function of charset any time we want, since 16383 is expected to be the minimum of the maximums.

FooBarrior · 2026-01-17T22:48:47Z

You can try to make tha max value variable if you want. Though it may require some research.

The problem is that we have (at least) three layers of charset settings:

system-wide
per-table
per-field

One overrides another. At some point, Filed would get a deduced value of charset, and perhaps Create_field would get it, too. Though it's hard to say, when exactly. Create_field has charset field in its parent Column_definition_attributes, you may check if it's set to the right encoding at different points in time.

You'd have to test all three cases though:

When a system-wide encoding is set
When it's overriden with table
When the latter is overriden with field charset.

Again, I'm NOT putting this as a requirement for this submission!

OsamaNabih · 2026-01-20T07:50:53Z

You can try to make tha max value variable if you want. Though it may require some research.

The problem is that we have (at least) three layers of charset settings:
* system-wide

* per-table

* per-field
One overrides another. At some point, Filed would get a deduced value of charset, and perhaps Create_field would get it, too. Though it's hard to say, when exactly. Create_field has charset field in its parent Column_definition_attributes, you may check if it's set to the right encoding at different points in time.

You'd have to test all three cases though:
* When a system-wide encoding is set

* When it's overriden with table

* When the latter is overriden with field charset.
Again, I'm NOT putting this as a requirement for this submission!

That is very informative.
I was mainly focusing on the CREATE TABLE scenario so I only paid attention to the system-wide encoding, but your comment made me realize there are other scenarios where T081 applies as well.
For example ALTER, CAST, CREATE TYPE...etc
For some of these scenarios, we need to handle the situation where the table/field were already created with a different charset than the system-wide one.

To verify my understanding, we are okay with limiting the scope of this PR to the CREATE TABLE scenario?

gkodinov

Thanks for working on this. This is a preliminary review.

Please fix some sanity checks:

Make sure this is a single commit and it has a proper commit message, according to CODING_STANDARDS.md.
Make sure there's no failing tests as a result of your change. I can see a couple in the buildbot results.

FooBarrior

Add more details in the commit comments. Mention SQL standard, its rule about implementation-defined lengths and describe our approach.
Remove Signed-off-by.

FooBarrior

Please go through the test carefully, by yourself. Because I see that my edit requests stay unfulfilled, yet marked as resolved.

FooBarrior

LGTM

Support SQL Standard T081 allowing the length to be ommitted for types VARCHAR, NVARCHAR, and VARBINARY In case of ommitted length for these types, we dothe following: VARCHAR, NVARCHAR are mapped to TEXT type VARBINARY is mapped to BLOB type This approach provides flexibility to the users And avoids complications with charsets and future ALTER table operations

gkodinov

LGTM

gkodinov · 2026-04-23T11:38:57Z

Note that, before being merged, this needs to go through testing. So please, have some more patience.

gkodinov

I've received the following request from the QA engineer:

Please add tests for other places where the length-less type can be used:

local stored procedure/function/trigger variables, via DECLARE
stored procedure/function parameters
local stored function return type
JSON_TABLE
dynamic columns
virtual columns

Note that the SP test should be done in both Oracle and native mode.

OsamaNabih · 2026-04-24T11:28:27Z

I've received the following request from the QA engineer:

Please add tests for other places where the length-less type can be used:

local stored procedure/function/trigger variables, via DECLARE

stored procedure/function parameters

local stored function return type

JSON_TABLE

dynamic columns

virtual columns

Note that the SP test should be done in both Oracle and native mode.

I'll start looking into those
Are these required as a part of the scope of this PR or for a future PR?

gkodinov · 2026-04-24T11:30:09Z

This is what is needed to:

document the feature fully
test it properly

So, I guess, for this PR. Note that it's about documenting and test coverage for the current behavior. It's not about changing it yet.

FooBarrior requested changes Jan 17, 2026

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Comment thread sql/sql_type.cc Outdated

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github-actions Bot added the External Contribution All PRs from entities outside of MariaDB Foundation, Corporation, Codership agreements. label Jan 18, 2026

OsamaNabih force-pushed the main branch 2 times, most recently from 17e0e30 to c6e985c Compare January 20, 2026 13:59

OsamaNabih closed this Jan 20, 2026

OsamaNabih reopened this Jan 20, 2026

OsamaNabih force-pushed the main branch 2 times, most recently from fe334ea to 7adad2c Compare January 20, 2026 14:08

FooBarrior requested changes Jan 23, 2026

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Comment thread mysql-test/main/varchar_no_length.cnf Outdated

Comment thread mysql-test/main/varchar_no_length.test Outdated

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OsamaNabih force-pushed the main branch 4 times, most recently from b0e32ff to 03b43df Compare February 4, 2026 20:02

gkodinov changed the title ~~[MDEV-31414] Implement optional lengths for string types~~ MDEV-31414: Implement optional lengths for string types Feb 19, 2026

gkodinov requested changes Feb 19, 2026

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OsamaNabih force-pushed the main branch 3 times, most recently from afe53e1 to 87cdc69 Compare February 24, 2026 10:49

FooBarrior requested changes Mar 3, 2026

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OsamaNabih force-pushed the main branch 4 times, most recently from 0a9f91e to 169b89e Compare March 4, 2026 10:57

FooBarrior requested changes Mar 5, 2026

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OsamaNabih force-pushed the main branch from 169b89e to f6254d5 Compare March 5, 2026 12:14

FooBarrior requested changes Mar 11, 2026

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OsamaNabih force-pushed the main branch from f6254d5 to 3e8114f Compare March 17, 2026 23:15

FooBarrior approved these changes Apr 21, 2026

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FooBarrior force-pushed the main branch from 3e8114f to ee5fe78 Compare April 21, 2026 16:22

gkodinov approved these changes Apr 23, 2026

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gkodinov requested a review from elenst April 23, 2026 11:41

gkodinov assigned elenst Apr 23, 2026

gkodinov requested changes Apr 24, 2026

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OsamaNabih commented Jan 17, 2026 •

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