Support duplicate column names in SDKs

[rekby]

For prevent customer unexpected issues after #3553

If result has duplicate column names and user access to one of them by name - SK must return error.
If user access to the column by index, or access to other columns (without name duplications) - sdk must work fine.

• feat: Support duplicated column names in result ydb-go-sdk#1204
• feature: Support duplicated column names in result ydb-python-sdk#419
• Support duplicated column names in result ydb-java-sdk#261
• Support duplicated column names in result (C++ SDK) #3886
• feat: Support duplicated column names in result ydb-php-sdk#138
• feat: Support duplicated column names in result ydb-nodejs-sdk#376
• Support duplicated column names in result ydb-dotnet-sdk#74
• Support duplicated column names in result ydb-rs-sdk#194

[alex268]

Why we must return error? It brokes some conversations like JDBC standard. From here Column names used as input to getter methods are case insensitive. When a getter method is called with a column name and several columns have the same name, the value of the first matching column will be returned.

[Zork33]

It's worth to discus. Since currently i.e. NodeJS SDK has no mechanism to fetch columns by index at all. As a solution, we could think about adding an index to the column name if the name is duplicated

[rekby]

Why we must return error? It brokes some conversations like JDBC standard.

This behavour will be at server queries and it is safest way - we always can start to support duplicated names, but it is difficult to change behavior.

may be reaction way need more research.

Main idea was:

1. Now we don't support duplicated names on server side
2. We will support duplicated names on server side in results
3. Safest way - deny use unexpected column

[alex268]

Our API has always supported the columns with any names, including duplicated. So these is no difference - does server support it or doesn't, the SDKs have to support it already. The only think we have to decide - the behavior of various SDKs must be equal. I checked Java SDK and it returns the last matching column - but it seems very as non conversational behavior. What about others SDK?

[rekby]

I think about it will be better to sync not only SDK, but server too - for have same behaviour of SDK and YQL/SQL.