PostgreSQL

  +
  Transmits the `+COPY+` data in the specified _`+buffer+`_, of length _`+nbytes+`_, to the server. The result is 1 if the data was queued, zero if it was not queued because of full buffers (this will only happen in nonblocking mode), or -1 if an error occurred. (Use `+PQerrorMessage+` to retrieve details if the return value is -1. If the value is zero, wait for write-ready and try again.)
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  The application can divide the `+COPY+` data stream into buffer loads of any convenient size. Buffer-load boundaries have no semantic significance when sending. The contents of the data stream must match the data format expected by the `+COPY+` command; see link:sql-copy.html[[.refentrytitle]#COPY#] for details.
[.term]#`+PQputCopyEnd+` ::
  Sends end-of-data indication to the server during `+COPY_IN+` state.
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Ends the `+COPY_IN+` operation successfully if _`+errormsg+`_ is `+NULL+`. If _`+errormsg+`_ is not `+NULL+` then the `+COPY+` is forced to fail, with the string pointed to by _`+errormsg+`_ used as the error message. (One should not assume that this exact error message will come back from the server, however, as the server might have already failed the `+COPY+` for its own reasons. Also note that the option to force failure does not work when using pre-3.0-protocol connections.)
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The result is 1 if the termination message was sent; or in nonblocking mode, this may only indicate that the termination message was successfully queued. (In nonblocking mode, to be certain that the data has been sent, you should next wait for write-ready and call `+PQflush+`, repeating until it returns zero.) Zero indicates that the function could not queue the termination message because of full buffers; this will only happen in nonblocking mode. (In this case, wait for write-ready and try the `+PQputCopyEnd+` call again.) If a hard error occurs, -1 is returned; you can use `+PQerrorMessage+` to retrieve details.
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After successfully calling `+PQputCopyEnd+`, call `+PQgetResult+` to obtain the final result status of the `+COPY+` command. One can wait for this result to be available in the usual way. Then return to normal operation.

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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 should be freed using `+PQfreemem+` when no longer needed.
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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).
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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.
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After `+PQgetCopyData+` returns -1, call `+PQgetResult+` to obtain the final result status of the `+COPY+` command. One can wait for this result to be available in the usual way. Then return to normal operation.

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  This function copies up to _`+length+`_-1 characters into the buffer and converts the terminating newline into a zero byte. `+PQgetline+` returns `+EOF+` at the end of input, 0 if the entire line has been read, and 1 if the buffer is full but the terminating newline has not yet been read.
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  Note that the application must check to see if a new line consists of the two characters `+\.+`, which indicates that the server has finished sending the results of the `+COPY+` command. If the application might receive lines that are more than _`+length+`_-1 characters long, care is needed to be sure it recognizes the `+\.+` line correctly (and does not, for example, mistake the end of a long data line for a terminator line).
[.term]#`+PQgetlineAsync+` ::
  Reads a row of `+COPY+` data (transmitted by the server) into a buffer without blocking.
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  This function is similar to `+PQgetline+`, but it can be used by applications that must read `+COPY+` data asynchronously, that is, without blocking. Having issued the `+COPY+` command and gotten a `+PGRES_COPY_OUT+` response, the application should call `+PQconsumeInput+` and `+PQgetlineAsync+` until the end-of-data signal is detected.
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  Unlike `+PQgetline+`, this function takes responsibility for detecting end-of-data.
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  On each call, `+PQgetlineAsync+` will return data if a complete data row is available in libpq's input buffer. Otherwise, no data is returned until the rest of the row arrives. The function returns -1 if the end-of-copy-data marker has been recognized, or 0 if no data is available, or a positive number giving the number of bytes of data returned. If -1 is returned, the caller must next call `+PQendcopy+`, and then return to normal processing.
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  The data returned will not extend beyond a data-row boundary. If possible a whole row will be returned at one time. But if the buffer offered by the caller is too small to hold a row sent by the server, then a partial data row will be returned. With textual data this can be detected by testing whether the last returned byte is `+\n+` or not. (In a binary `+COPY+`, actual parsing of the `+COPY+` data format will be needed to make the equivalent determination.) The returned string is not null-terminated. (If you want to add a terminating null, be sure to pass a _`+bufsize+`_ one smaller than the room actually available.)
[.term]#`+PQputline+` ::
  Sends a null-terminated string to the server. Returns 0 if OK and `+EOF+` if unable to send the string.
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The `+COPY+` data stream sent by a series of calls to `+PQputline+` has the same format as that returned by `+PQgetlineAsync+`, except that applications are not obliged to send exactly one data row per `+PQputline+` call; it is okay to send a partial line or multiple lines per call.
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[NOTE]
====
==== Note

  Before PostgreSQL protocol 3.0, it was necessary for the application to explicitly send the two characters `+\.+` as a final line to indicate to the server that it had finished sending `+COPY+` data. While this still works, it is deprecated and the special meaning of `+\.+` can be expected to be removed in a future release. It is sufficient to call `+PQendcopy+` after having sent the actual data.
  ====
[.term]#`+PQputnbytes+` ::
  Sends a non-null-terminated string to the server. Returns 0 if OK and `+EOF+` if unable to send the string.
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  This is exactly like `+PQputline+`, except that the data buffer need not be null-terminated since the number of bytes to send is specified directly. Use this procedure when sending binary data.
[.term]#`+PQendcopy+` ::
  Synchronizes with the server.
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This function waits until the server has finished the copying. It should either be issued when the last string has been sent to the server using `+PQputline+` or when the last string has been received from the server using `+PQgetline+`. It must be issued or the server will get [.quote]#“[.quote]#out of sync#”# with the client. Upon return from this function, the server is ready to receive the next SQL command. The return value is 0 on successful completion, nonzero otherwise. (Use `+PQerrorMessage+` to retrieve details if the return value is nonzero.)
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When using `+PQgetResult+`, the application should respond to a `+PGRES_COPY_OUT+` result by executing `+PQgetline+` repeatedly, followed by `+PQendcopy+` after the terminator line is seen. It should then return to the `+PQgetResult+` loop until `+PQgetResult+` returns a null pointer. Similarly a `+PGRES_COPY_IN+` result is processed by a series of `+PQputline+` calls followed by `+PQendcopy+`, then return to the `+PQgetResult+` loop. This arrangement will ensure that a `+COPY+` command embedded in a series of SQL commands will be executed correctly.
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Older applications are likely to submit a `+COPY+` via `+PQexec+` and assume that the transaction is done after `+PQendcopy+`. This will work correctly only if the `+COPY+` is the only SQL command in the command string.