BUFFER-COPY statement

Performs a bulk copy of a source record to a target record by copying each source field to the target field of the same name. You can specify a list of fields to exclude from the bulk copy, or a list of fields to include in the bulk copy. You can also specify WHEN...THEN phrases. For each such phrase, BUFFER-COPY executes the THEN portion if the corresponding WHEN portion evaluates to TRUE.

Syntax


BUFFER-COPY `source` [ { EXCEPT \| USING } `field` ... ] TO `target` [ ASSIGN `assign-expression` ... ] [ NO-LOBS ] [ NO-ERROR ]

source

The source database table, buffer, temp-table, or work table.

EXCEPT field ...

A list of space-separated source fields to exclude from the bulk copy.

USING field ...

A list of space-separated source fields to include in the bulk copy. The USING option is simply a positive version of the EXCEPT option.

TO target

The source database table, buffer, temp-table, or work table.

ASSIGN assign-expression

A space-separated list of any valid ABL ASSIGN statements (without the EXCEPT option, which BUFFER-COPY already provides). BUFFER-COPY performs each assign-expression and automatically excludes the field on the left side (“destination”) of each assign-expression from the bulk copy-except for field extents (subscripted fields). If a field extent appears on the left side of an assign-expression, BUFFER-COPY does not automatically exclude that extent (such as customer.mnth-sales[1]) or the field as a whole (such as customer.mnth-sales) from the bulk copy.

NO-LOBS

Directs the AVM to ignore large object data when copying records that contain BLOB or CLOB fields.

Caution: Using this option can create the potential for errors in your data and lead to inappropriate results. Therefore, before using this option, you must understand the nature of your data and be sure that logic using this option will not result in inconsistent or out-of-date data in the database.

NO-ERROR

Suppresses ABL errors or error messages that would otherwise occur and diverts them to the ERROR-STATUS system handle. If an error occurs, the action of the statement is not done and execution continues with the next statement. If the statement fails, any persistent side-effects of the statement are backed out. If the statement includes an expression that contains other executable elements, like methods, the work performed by these elements may or may not be done, depending on the order the AVM resolves the expression elements and the occurrence of the error.

To check for errors after a statement that uses the NO-ERROR option:

Check the ERROR-STATUS:ERROR attribute to see if the AVM raised the ERROR condition.

Check if the ERROR-STATUS:NUM-MESSAGES attribute is greater than zero to see if the AVM generated error messages. ABL handle methods used in a block without a CATCH end block treat errors as warnings and do not raise ERROR, do not set the ERROR-STATUS:ERROR attribute, but do add messages to the ERROR-STATUS system handle. Therefore, this test is the better test for code using handle methods without CATCH end blocks. ABL handle methods used in a block with a CATCH end block raise ERROR and add messages to the error object generated by the AVM. In this case, the AVM does not update the ERROR-STATUS system handle.

Use ERROR-STATUS:GET-MESSAGE( message-num ) to retrieve a particular message, where message-num is 1 for the first message.

If the statement does not include the NO-ERROR option, you can use a CATCH end block to handle errors raised by the statement.

Some other important usage notes on the NO-ERROR option:

NO-ERROR does not suppress errors that raise the STOP or QUIT condition.

A CATCH statement, which introduces a CATCH end block, is analogous to a NO-ERROR option in that it also suppresses errors, but it does so for an entire block of code. It is different in that the error messages are contained in a class-based error object (generated by the AVM or explicitly thrown), as opposed to the ERROR-STATUS system handle. Also, if errors raised in the block are not handled by a compatible CATCH block, ON ERROR phrase, or UNDO statement, then the error is not suppressed, but handled with the default error processing for that block type.

When a statement contains the NO-ERROR option and resides in a block with a CATCH end block, the NO-ERROR option takes precedence over the CATCH block. That is, an error raised on the statement with the NO-ERROR option will not be handled by a compatible CATCH end block. The error is redirected to the ERROR-STATUS system handle as normal.

If an error object is thrown to a statement that includes the NO-ERROR option, then the information and messages in the error object will be used to set the ERROR-STATUS system handle. This interoperability feature is important for those integrating code that uses the traditional NO-ERROR technique with the newer, structured error handling that features error objects and CATCH end blocks.

Notes

At compile time, BUFFER-COPY:

Fails to compile if any source-target field pair is not type compatible

Excludes from the bulk copy all EXCEPT field fields, and all assign-expression fields on the left side of the assignment

Automatically excludes fields that appear in the source but not the target from the bulk copy

Tries to bind unqualified field names that appear in the EXCEPT and USING options to the source buffer

At run time, BUFFER-COPY:

Creates a target record if none already exists and executes any applicable CREATE triggers

Assigns all matching fields that do not appear in the EXCEPT or ASSIGN options

Performs each assign-expression in the ASSIGN option, one-by-one

The BUFFER-COPY statement, like the VALIDATE statement, must appear within the scope of a FIND, a FOR EACH, or a CREATE statement that references the source table.

If a BUFFER-COPY statement references a target buffer for the first time, ABL regards this reference as a “free reference” and scopes the buffer to the nearest enclosing block that can scope records. For more information on free references, see the chapter on block properties in OpenEdge Getting Started: ABL Essentials.

With respect to transaction processing, ABL treats a BUFFER-COPY statement the same way it would treat equivalent ASSIGN statements. For more information on transaction processing, see the chapter on transactions in OpenEdge Getting Started: ABL Essentials.

The compiler’s XREF facility automatically creates a REFERENCE for each field in the fields list, a TABLE-REFERENCE for the source and target buffers, ACCESS and UPDATE references for any fields in the ASSIGN option, and ACCESS (or UPDATE) references for each source (or target) field that participates in the bulk copy.

When copying records that contain a BLOB or CLOB field, the AVM copies the object data associated with the source record to the target record. If the BLOB or CLOB field in the source record contains the Unknown value (?), the AVM stores the Unknown value (?) in the BLOB or CLOB field of the target record. If the target record already has object data associated with it, the AVM deletes that object data before copying the new object data.

Use the NO-LOBS option with the BUFFER-COPY statement to ignore large object data when copying records that contain BLOB or CLOB fields. More specifically:

When you copy a source record to a new target record, the AVM sets the value of the BLOB or CLOB field in the target record to the Unknown value (?).

When you copy a source record to an existing target record, the AVM does not change the value of the BLOB or CLOB field in the existing target record.

You can also use the EXCEPT option to exclude BLOB and CLOB fields from the copy.