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PostgreSQL Reference Manual - Volume 2 - Programming Guide
by The PostgreSQL Global Development Group
Paperback (6"x9"), 408 pages
ISBN 0954612035
RRP £19.95 ($34.95)

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1.8.2 Functions for Receiving COPY Data

These functions are used to receive data during COPY TO STDOUT. They will fail if called when the connection is not in COPY_OUT state.

PQgetCopyData
Receives data from the server during COPY_OUT state.
int PQgetCopyData(PGconn *conn,
                  char **buffer,
                  int async);
Attempts to obtain another row of data from the server during a COPY. Data is always returned one data row at a time; if only a partial row is available, it is not returned. Successful return of a data row involves allocating a chunk of memory to hold the data. The buffer parameter must be non-NULL. *buffer is set to point to the allocated memory, or to NULL in cases where no buffer is returned. A non-NULL result buffer must be freed using PQfreemem when no longer needed. When a row is successfully returned, the return value is the number of data bytes in the row (this will always be greater than zero). The returned string is always null-terminated, though this is probably only useful for textual COPY. A result of zero indicates that the COPY is still in progress, but no row is yet available (this is only possible when async is true). A result of -1 indicates that the COPY is done. A result of -2 indicates that an error occurred (consult PQerrorMessage for the reason). When async is true (not zero), PQgetCopyData will not block waiting for input; it will return zero if the COPY is still in progress but no complete row is available. (In this case wait for read-ready and then call PQconsumeInput before calling PQgetCopyData again.) When async is false (zero), PQgetCopyData will block until data is available or the operation completes. After PQgetCopyData returns -1, call PQgetResult to obtain the final result status of the COPY command. One may wait for this result to be available in the usual way. Then return to normal operation.
ISBN 0954612035PostgreSQL Reference Manual - Volume 2 - Programming GuideSee the print edition