Bryan, I am out sick for last couple of days so I haven't been able to follow the entire recent thread about collation support but let me describe to you briefly what I have gathered so far.
Let me talk in terms of SQL datatype CHAR to keep this simple and contained. Similar rules will apply for VARCHAR, LONG VARCHAR and CLOB datatypes. The main issue is as far as the user is concerned, there is one CHAR datatype when s/he defines their tables. But if they have asked for territory based collation, then we want these CHAR datatypes to collate differently than the CHAR datatypes that exist today in 10.2 And if the user hasn't requested territory based collation, then we want these CHAR datatypes to collate the way they do in 10.2 today. So, in short, the CHAR datatype in 10.3 will have different collation behavior depending on what user has requested. But as far as the user is concerned, they are just SQL CHAR datatypes and not new SQL datatypes. In my original proposal, I had proposed to introduce new internal CHAR datatype which extended current CHAR datatype in Derby. I was proposing to implement them by having a new format id associated with the new internal CHAR datatypes. But with my proposal, there is overhead associated with implementing new getter methods in DataValueFactory for this new internal datatype and the type compiler associated with the new internal datatype etc. The other issue with my proposal was that there are many places in the code today where we get character datatypes and all of those cases will have to be inidividually investigated to see which CHAR datatype implementation they should use. So, if the character datatype is getting instantiated for CHAR columns in system tables, then we should use existing CHAR datatype implementation. But, if they were getting instantiated for user table, then the new internal CHAR datatype should be instantiated. AND there will be places where we can't determine which one of the two CHAR implementations should we use, for eg a string value in a query 'abc'. What Dan is proposing is that we should keep in mind that CHAR with territory based collation differ from the CHAR with default collation in only one aspect and ie how they are collated. Rest everything is same. So, as long as we know at the collation time, which kind of collation we are dealing with, we should be fine and hence there is no need to generate new internal CHAR datatypes. Dan is proposing that at compile time, when we associate a DataTypeDescriptor (DTD) with a char column, we tell what kind of collation should be associated with that DTD. The collation associated can be UCS_BASIC/territory base/unknown. Char columns associated with SYS schemas will always have UCS_BASIC in DTD associated with them. Char columns from user schema will have UCS_BASIC/territory based depending on what user has requested through COLLATION attribute in the jdbc url at database create time. Char columns that are not associated with a specific schema will have their DTD marked with collation as unknown and later on, at the actual collation time, for eg like method, compare methods, their collation will be determined depending on what the other operand's collation is. If the collation of other operand is also unknown, then the collation attribute of such Char will default to whatever COLLATION attribute user has requested at database create time. So, as you can see, collation information will be saved at the column level in language layer. Store will follow the same granularity and it will write the collation type for each and every column in it's metadata (ie for char datatypes as well as non-char datatypes). This collation type will make sense for only char datatypes. For the other datatypes, collation type will be ignored. Some of the complexity is coming from the fact that a single database can have 2 different collations associated with it's columns, ie, SYS schema will always use UCS_BASIC for it's collation. But all the user schemas will use either UCS_BASIC/territory based collation. If the collation was of only one type for the entire database, the design/implementation would have been far easier and we could keep collation information at database level rather than column level. Bryan, I might have given more information/depth than what you were looking for but this is also helping me make sure that I am on the same page as rest of the people involved in/following the collation discussion thread. Dan, Mike, Rick, and others following the threads on collation, please feel free to pitch in and add more to what I have covered or correct if I have incorrect information. thanks, Mamta On 3/16/07, Bryan Pendleton <[EMAIL PROTECTED]> wrote:
I'm afraid I struggled a bit to follow all the threads about the new collation support. Would it be possible for someone to briefly summarize: - what the major issues are, and - what the primary proposals are thanks, bryan
