github-actions[bot] commented on code in PR #68640:
URL: https://github.com/apache/doris/pull/68640#discussion_r4311580799
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fe/fe-core/src/main/java/org/apache/doris/mysql/MysqlSerializer.java:
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@@ -218,8 +220,10 @@ public void writeField(String db, String table, Column
column, boolean sendDefau
writeInt4(getMysqlTypeLength(column.getType()));
// Column type: one byte integer
writeInt1(getMysqlResultType(column.getType()).getCode());
- // Flags: two byte integer
- writeInt2(getMysqlFlags(column.getType()));
+ // Flags: two byte integer. Callers pass either the read or the
display schema column, so the
+ // NOT_NULL flag describes exactly the schema view this packet
carries: a COM_FIELD_LIST built from
+ // the display columns reports the same NOT NULL as SHOW COLUMNS.
+ writeInt2(getMysqlFlags(column.getType()) | (column.isAllowNull() ? 0
: NOT_NULL_FLAG));
Review Comment:
[P2] Preserve result nullability in prepared-statement metadata
This overload is also used by `MysqlResultSender.sendStmtPrepareOK()` with
`slotReference.getOriginalColumn()` and `sendDefault=false`. For `SELECT r.id
FROM l LEFT JOIN r ON l.id = r.id` with `r.id NOT NULL`,
`JoinUtils.getJoinOutput()` makes the output slot nullable but
`SlotReference.withNullable()` retains the non-nullable original column. The
new flag therefore tells `COM_STMT_PREPARE` clients that `r.id` cannot be NULL,
even though unmatched rows return NULL. Keep the declared-column flag confined
to `COM_FIELD_LIST`, or pass the output slot's nullability on the prepare path,
and add a packet assertion for the nullable side of an outer join.
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