Timestamp display precision should respect column schema

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Description

What type of enhancement is this?

User experience

What does the enhancement do?

Currently, when querying GreptimeDB through the MySQL CLI, timestamp rendering does not always respect the timestamp precision defined by the column schema. (Maybe pg cli also has this problem)

For example

create table

CREATE TABLE ts_precision_test (
    ts_s  TIMESTAMP(0),
    ts_ms TIMESTAMP(3),
    ts_us TIMESTAMP(6),
    ts_ns TIMESTAMP(9),
    v     INT32,
    TIME INDEX (ts_ms),
    PRIMARY KEY (v)
);

insert data

INSERT INTO ts_precision_test VALUES (
    '2026-06-02 03:50:00',
    '2026-06-02 03:50:00.195',
    '2026-06-02 03:50:00.195123',
    '2026-06-02 03:50:00.195123456',
    1
);

query data

SELECT * FROM ts_precision_test;

actual output

+---------------------+----------------------------+----------------------------+----------------------------+------+
| ts_s                | ts_ms                      | ts_us                      | ts_ns                      | v    |
+---------------------+----------------------------+----------------------------+----------------------------+------+
| 2026-06-02 03:50:00 | 2026-06-02 03:50:00.195000 | 2026-06-02 03:50:00.195123 | 2026-06-02 03:50:00.195123 |    1 |
+---------------------+----------------------------+----------------------------+----------------------------+------+

expected output

+---------------------+----------------------------+----------------------------+-------------------------------+------+
| ts_s                | ts_ms                      | ts_us                      | ts_ns                         | v    |
+---------------------+----------------------------+----------------------------+-------------------------------+------+
| 2026-06-02 03:50:00 | 2026-06-02 03:50:00.195    | 2026-06-02 03:50:00.195123 | 2026-06-02 03:50:00.195123456 |    1 |
+---------------------+----------------------------+----------------------------+-------------------------------+------+

Implementation challenges

No response

Guia do colaborador

Direção de pesquisa: Inspecione o código de formatação de timestamp no manipulador de protocolo MySQL. Identifique onde a precisão de exibição é determinada e garanta que corresponda à precisão do esquema da coluna (segundos, milissegundos, microssegundos, nanossegundos).
Pilha de tecnologia: rust
Domain: backend
Tipo Issue: Funcionalidade
Difficulty: 2
Tempo estimado: Meio dia
Status da atividade: Recente
Clarity: Claro
Prerequisites: Rust
Simpatia para novatos: 65