Yan Yan created SPARK-56652:
-------------------------------
Summary: DESCRIBE EXTENDED should always emit RELY/NORELY for
constraints, matching SHOW CREATE TABLE
Key: SPARK-56652
URL: https://issues.apache.org/jira/browse/SPARK-56652
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 4.2.0
Reporter: Yan Yan
After SPARK-52141 (DESCRIBE EXTENDED constraint output) and SPARK-52142
(SHOW CREATE TABLE constraint output) landed, the two surfaces render
the same constraint asymmetrically:
|| Constraint state || DESCRIBE EXTENDED || SHOW CREATE TABLE ||
| PRIMARY KEY (default) | {{PRIMARY KEY (a) NOT ENFORCED}} | {{PRIMARY KEY (a)
NOT ENFORCED NORELY}} |
| PRIMARY KEY with RELY | {{PRIMARY KEY (a) NOT ENFORCED RELY}} | {{PRIMARY KEY
(a) NOT ENFORCED RELY}} |
| CHECK (default) | {{CHECK (...) ENFORCED}} | {{CHECK (...) ENFORCED NORELY}} |
{{BaseConstraint.toDescription()}} (used by {{DescribeTableExec}})
skips the {{NORELY}} token when {{rely=false}}, while
{{BaseConstraint.toDDL()}} (used by {{ShowCreateTableExec}}) always
emits {{RELY|NORELY}}.
The original review on [PR
#51577|https://github.com/apache/spark/pull/51577#discussion_r2223415193]
suggested skipping both {{NOT ENFORCED}} and {{NORELY}} when at the
default value. The implementation only skipped {{NORELY}} (because
{{ENFORCED}}'s default is per-subclass and not visible to
{{BaseConstraint}}), leaving {{NOT ENFORCED}} always emitted. The
result is a confusing user experience where the rely state is hidden
in DESCRIBE EXTENDED but exposed in SHOW CREATE TABLE for the same
constraint.
This issue proposes making {{toDescription()}} always emit
{{RELY|NORELY}}, so both surfaces consistently render the full
enforcement and rely state. The natural invariant becomes:
{code:java}
toDDL == "CONSTRAINT " + name + " " + toDescription
{code}
User-facing impact: DESCRIBE EXTENDED for default-rely constraints
will now print {{NORELY}} explicitly. Example before/after:
{code}
-- before
DESC EXTENDED tbl
...
# Constraints
pk_table_pk PRIMARY KEY (id) NOT ENFORCED
uk_b UNIQUE (b) NOT ENFORCED
c1 CHECK (c IS NOT NULL) ENFORCED
-- after
DESC EXTENDED tbl
...
# Constraints
pk_table_pk PRIMARY KEY (id) NOT ENFORCED NORELY
uk_b UNIQUE (b) NOT ENFORCED NORELY
c1 CHECK (c IS NOT NULL) ENFORCED NORELY
{code}
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