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[datatype] fix equals method for udt datatypes across schema upgrades #531

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[datatype] fix equals method for udt datatypes across schema upgrades #531

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14 changes: 10 additions & 4 deletions src/data_type.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,8 @@
#include "types.hpp"
#include "vector.hpp"

#include <algorithm>

namespace datastax { namespace internal { namespace core {

class Collection;
Expand Down Expand Up @@ -365,11 +367,15 @@ class UserType : public DataType {
return false;
}

if (fields_.size() != user_type->fields_.size()) {
return false;
}

for (size_t i = 0; i < fields_.size(); ++i) {
// UDT's can be considered equal as long as the mutual first fields shared
// between them are equal. UDT's are append only as far as fields go, so a
// newer 'version' of the UDT data type after a schema change event should be
// treated as equivalent in this scenario, by simply looking at the first N
// mutual fields they should share.
size_t min_fields_size = std::min(fields_.size(), user_type->fields_.size());
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This seems reasonable to me. It does seem that after creating a type that a type can only be altered in the following ways:

  • Rename field: ALTER TYPE address RENAME zip TO zipcode AND street_name TO street
  • Add a field: ALTER TYPE address ADD country text

It'd be nice to have some tests that verify this is a correct assumption.

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It'd be nice to have some tests that verify this is a correct assumption.

I'm not entirely sure how we would test that? Are you suggesting we try to test that the database rejects invalid DDL?

There is a third way, you can change the type of a field ALTER field_name TYPE new_cql_datatype - however, I think if you're doing this, you probably need to redeploy your application anyways since the types are changing.


for (size_t i = 0; i < min_fields_size; ++i) {
if (fields_[i].name != user_type->fields_[i].name ||
!fields_[i].type->equals(user_type->fields_[i].type)) {
return false;
Expand Down