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>Chapter 33. <SPAN
CLASS="APPLICATION"
>ECPG</SPAN
> - Embedded <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
> in C</TD
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><H1
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><A
NAME="ECPG-LIBRARY"
>33.11. Library Functions</A
></H1
><P
> The <TT
CLASS="FILENAME"
>libecpg</TT
> library primarily contains
<SPAN
CLASS="QUOTE"
>"hidden"</SPAN
> functions that are used to implement the
functionality expressed by the embedded SQL commands. But there
are some functions that can usefully be called directly. Note that
this makes your code unportable.
</P
><P
></P
><UL
><LI
><P
> <CODE
CLASS="FUNCTION"
>ECPGdebug(int <TT
CLASS="REPLACEABLE"
><I
>on</I
></TT
>, FILE
*<TT
CLASS="REPLACEABLE"
><I
>stream</I
></TT
>)</CODE
> turns on debug
logging if called with the first argument non-zero. Debug logging
is done on <TT
CLASS="REPLACEABLE"
><I
>stream</I
></TT
>. The log contains
all <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
> statements with all the input
variables inserted, and the results from the
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> server. This can be very
useful when searching for errors in your <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
>
statements.
</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
> On Windows, if the <SPAN
CLASS="APPLICATION"
>ecpg</SPAN
> libraries and an application are
compiled with different flags, this function call will crash the
application because the internal representation of the
<TT
CLASS="LITERAL"
>FILE</TT
> pointers differ. Specifically,
multithreaded/single-threaded, release/debug, and static/dynamic
flags should be the same for the library and all applications using
that library.
</P
></BLOCKQUOTE
></DIV
></LI
><LI
><P
> <CODE
CLASS="FUNCTION"
>ECPGget_PGconn(const char *<TT
CLASS="REPLACEABLE"
><I
>connection_name</I
></TT
>)
</CODE
> returns the library database connection handle identified by the given name.
If <TT
CLASS="REPLACEABLE"
><I
>connection_name</I
></TT
> is set to <TT
CLASS="LITERAL"
>NULL</TT
>, the current
connection handle is returned. If no connection handle can be identified, the function returns
<TT
CLASS="LITERAL"
>NULL</TT
>. The returned connection handle can be used to call any other functions
from <SPAN
CLASS="APPLICATION"
>libpq</SPAN
>, if necessary.
</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
> It is a bad idea to manipulate database connection handles made from <SPAN
CLASS="APPLICATION"
>ecpg</SPAN
> directly
with <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> routines.
</P
></BLOCKQUOTE
></DIV
></LI
><LI
><P
> <CODE
CLASS="FUNCTION"
>ECPGtransactionStatus(const char *<TT
CLASS="REPLACEABLE"
><I
>connection_name</I
></TT
>)</CODE
>
returns the current transaction status of the given connection identified by <TT
CLASS="REPLACEABLE"
><I
>connection_name</I
></TT
>.
See <A
HREF="libpq-status.html"
>Section 31.2</A
> and libpq's <CODE
CLASS="FUNCTION"
>PQtransactionStatus()</CODE
> for details about the returned status codes.
</P
></LI
><LI
><P
> <CODE
CLASS="FUNCTION"
>ECPGstatus(int <TT
CLASS="REPLACEABLE"
><I
>lineno</I
></TT
>,
const char* <TT
CLASS="REPLACEABLE"
><I
>connection_name</I
></TT
>)</CODE
>
returns true if you are connected to a database and false if not.
<TT
CLASS="REPLACEABLE"
><I
>connection_name</I
></TT
> can be <TT
CLASS="LITERAL"
>NULL</TT
>
if a single connection is being used.
</P
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