Sophie: libpq++-devel-4.0-12mdv2008.0 i586

libpq++-devel-4.0-12mdv2008.0.i586.rpm

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>Functions Associated with the COPY Command</TITLE
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><H1
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><A
NAME="libpqpp-copy"
>1.7. Functions Associated with the COPY Command</A
></H1
>   
   
   <P
>    The <TT
CLASS="COMMAND"
>COPY</TT
> command in <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> 
    has options to read from or write to the network
    connection used by <SPAN
CLASS="APPLICATION"
>libpq++</SPAN
>.  
    Therefore, functions are necessary to
    access this network connection directly so applications may take full
    advantage of this capability.
    
    <P
></P
></P><UL
><LI
>      <P
>       <TT
CLASS="FUNCTION"
>PgDatabase::GetLine</TT
>
       reads a newline-terminated line of characters (transmitted by the
       backend server) into a buffer 
       <TT
CLASS="REPLACEABLE"
><I
>string</I
></TT
>
       of size <TT
CLASS="REPLACEABLE"
><I
>length</I
></TT
>.
</P><PRE
CLASS="SYNOPSIS"
>int PgDatabase::GetLine(char* string, int length)</PRE
><P>
      </P
>

      <P
>       Like the Unix system routine
       <TT
CLASS="FUNCTION"
>fgets()</TT
>,
       this routine copies up to 
       <TT
CLASS="LITERAL"
><TT
CLASS="REPLACEABLE"
><I
>length</I
></TT
>-1</TT
>
       characters into 
       <TT
CLASS="REPLACEABLE"
><I
>string</I
></TT
>.
       It is like 
       <TT
CLASS="FUNCTION"
>gets()</TT
>,
       however, in that it converts the terminating newline into a zero byte.
      </P
>
      <P
>       <TT
CLASS="FUNCTION"
>PgDatabase::GetLine</TT
>
       returns <TT
CLASS="SYMBOL"
>EOF</TT
> at end of file, 0 if the entire line has been read, and 1 if the
       buffer is full but the terminating newline has not yet been read.
      </P
>
      <P
>       Notice that the application must check to see if a new line consists
       of a backslash followed by a period (<TT
CLASS="LITERAL"
>\.</TT
>), which indicates
       that the backend
       server has finished sending the results of the 
       <TT
CLASS="COMMAND"
>COPY</TT
>.
       Therefore, if the application ever expects to receive lines
       that are more than
       <TT
CLASS="LITERAL"
><TT
CLASS="REPLACEABLE"
><I
>length</I
></TT
>-1</TT
>
       characters long, the application must be sure to check the return
       value of <TT
CLASS="FUNCTION"
>PgDatabase::GetLine</TT
> very carefully.
      </P
>
     </LI
><LI
>      <P
>       <TT
CLASS="FUNCTION"
>PgDatabase::PutLine</TT
>
       Sends a null-terminated <TT
CLASS="REPLACEABLE"
><I
>string</I
></TT
>
       to the backend server.
</P><PRE
CLASS="SYNOPSIS"
>void PgDatabase::PutLine(char* string)</PRE
><P>
      </P
>
      <P
>       The application must explicitly send the characters <TT
CLASS="LITERAL"
>\.</TT
>
       to indicate to the backend that it has finished sending its data.
      </P
>
     </LI
><LI
>      <P
>       <TT
CLASS="FUNCTION"
>PgDatabase::EndCopy</TT
>
       synchronizes with the backend.
</P><PRE
CLASS="SYNOPSIS"
>int PgDatabase::EndCopy()</PRE
><P>
       This function waits until the backend has
       finished processing the <TT
CLASS="COMMAND"
>COPY</TT
>.
       It should either be issued when the
       last string has been sent to the backend using
       <TT
CLASS="FUNCTION"
>PgDatabase::PutLine</TT
>
       or when the last string has been received from the backend using
       <TT
CLASS="FUNCTION"
>PgDatabase::GetLine</TT
>.
       It must be issued or the backend may get <SPAN
CLASS="QUOTE"
>"out of sync"</SPAN
> with
       the frontend.  Upon return from this function, the backend is ready to
       receive the next command.
      </P
>	    
      <P
>       The return value is 0 on successful completion, nonzero otherwise.
      </P
>
     </LI
></UL
><P>
   </P
>

   <P
>    As an example:
    
</P><PRE
CLASS="PROGRAMLISTING"
>PgDatabase data;
data.Exec("CREATE TABLE foo (a int4, b char(16), d double precision)");
data.Exec("COPY foo FROM STDIN");
data.PutLine("3\tHello World\t4.5\n");
data.PutLine("4\tGoodbye World\t7.11\n");
...
data.PutLine("\\.\n");
data.EndCopy();</PRE
><P>
   </P
>
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