[reshke]

ALTER COLUMN TYPE looked up a default hash operator class without checking whether its support functions can hash the concrete element or field types. For example, this left an empty table distributed by money[]:

CREATE TABLE t (k int[]) DISTRIBUTED BY (k);
ALTER TABLE t ALTER COLUMN k TYPE money[] USING k::money[];
INSERT INTO t VALUES (ARRAY[1::money]);
ERROR: could not identify a hash function for type money

Both array types select array_ops, so ATPrepAlterColumnType considered their distribution compatible even though money has no default hash support. Use cdb_default_distribution_opclass_for_type, as CREATE TABLE does, so the existing incompatible-type handling also covers containers: reject the change on a populated table, or switch an empty table to random distribution.

Add coverage for both cases and for a compatible int[] to bigint[] change.

Fixes #ISSUE_Number

What does this PR do?

Type of Change

• Bug fix (non-breaking change)
• New feature (non-breaking change)
• Breaking change (fix or feature with breaking changes)
• Documentation update

Breaking Changes

Test Plan

• Unit tests added/updated
• Integration tests added/updated
• Passed make installcheck
• Passed make -C src/test installcheck-cbdb-parallel

Impact

Performance:

User-facing changes:

Dependencies:

Checklist

• Followed contribution guide
• Added/updated documentation
• Reviewed code for security implications
• This PR contains AI-assisted code generation
• Requested review from cloudberry committers

Additional Context

CI Skip Instructions

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[my-ship-it]

LGTM ,thanks

[my-ship-it]

Some cases not covered:

case 1

SET gp_use_legacy_hashops = on;
CREATE TABLE lm (m money, x int) DISTRIBUTED BY (m); 
CREATE TABLE c AS SELECT * FROM lm; 
ERROR:  cache lookup failed for opclass 0 (lsyscache.c:1365)

case 2

CREATE TYPE ct AS (a int);
CREATE TABLE tc (c ct, x int) DISTRIBUTED BY (c);
ALTER TYPE ct ADD ATTRIBUTE m money; 
INSERT INTO tc VALUES (ROW(2, 2::money)::ct, 2);
ERROR:  could not identify a hash function for type money
SELECT count(*) FROM tc WHERE c = ROW(1,NULL)::ct;
ERROR:  could not identify a hash function for type money

[reshke]

Some cases not covered:

case 1

SET gp_use_legacy_hashops = on;
CREATE TABLE lm (m money, x int) DISTRIBUTED BY (m); 
CREATE TABLE c AS SELECT * FROM lm; 
ERROR:  cache lookup failed for opclass 0 (lsyscache.c:1365)

case 2

CREATE TYPE ct AS (a int);
CREATE TABLE tc (c ct, x int) DISTRIBUTED BY (c);
ALTER TYPE ct ADD ATTRIBUTE m money; 
INSERT INTO tc VALUES (ROW(2, 2::money)::ct, 2);
ERROR:  could not identify a hash function for type money
SELECT count(*) FROM tc WHERE c = ROW(1,NULL)::ct;
ERROR:  could not identify a hash function for type money

Yes, thx, this report looks related, will fix inside this PR