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<a name="19981">
</a><h3>Example 7: postgres</h3>
<p><a name="19982">
</a>The following example shows how to create a database driver. This `postgres' module is a database services driver which allows the AOLserver to use the <i>Postgres95</i> database. </p>
<p><a name="19986">
</a>This example can be found in the <code>examples/c/postgres</code> directory.</p>
<pre>    <a name="19987"></a>
    <a name="19988"></a>#include "ns.h"
    <a name="19989"></a>#include "nsdb.h"
    <a name="19990"></a>#include "nstcl.h"
    <a name="19991"></a>#include "libpq-fe.h"
    <a name="19992"></a>#include &lt;string.h&gt;
    <a name="19993"></a>#include &lt;assert.h&gt;
    <a name="19994"></a>
    <a name="19995"></a>/*-
    <a name="19996"></a>
    <a name="19997"></a>What is this?
    <a name="19998"></a>------------
    <a name="19999"></a>
    <a name="20003"></a>This module implements a simple AOLserver database services driver.  A
    <a name="20007"></a>database driver is a module which interfaces between the AOLserver
    <a name="20008"></a>database-independent nsdb module and the API of a particular DBMS.  A
    <a name="20009"></a>database driver's job is to open connections, send SQL statements, and
    <a name="20010"></a>translate the results into the form used by nsdb.  In this case, the
    <a name="20011"></a>driver is for the Postgres95 DBMS from UC Berekely.  Postgres95 can be
    <a name="20012"></a>downloaded and installed on most Unix systems.  To use this driver, you
    <a name="20013"></a>must have Postgres95 installed on your system.  For more information on
    <a name="20014"></a>Postgres95 or to download the code, open:
    <a name="20015"></a>
    <a name="20016"></a>        http://s2k-ftp.cs.berkeley.edu:8000/postgres95
    <a name="20017"></a>
    <a name="20018"></a>
    <a name="20019"></a>How does it work?
    <a name="20020"></a>----------------
    <a name="20021"></a>
    <a name="20025"></a>Driver modules look much like ordinary AOLserver modules but are
    <a name="20026"></a>loaded differently.  Instead of being listed with other modules in the
    <a name="20027"></a>[ns\server\&lt;server-name&gt;\modules] configuration section, a database
    <a name="20028"></a>driver is listed in the [ns\module\nsdb\drivers] section and nsdb does
    <a name="20029"></a>the loading.  The database driver initialization function normally does
    <a name="20030"></a>little more than call the nsdb Ns_DbRegisterDriver() function with an
    <a name="20031"></a>array of pointers to functions.  The functions are then later used by
    <a name="20032"></a>nsdb to open database connections and send and process queries. 
    <a name="20033"></a>In addition to open,
    <a name="20034"></a>select, and getrow functions, the driver also provides system catalog
    <a name="20035"></a>functions and a function for initializing a virtual server.  The
    <a name="20036"></a>virtual server initialization function is called each time nsdb is
    <a name="20037"></a>loaded into a virtual server.  In this case, the server initialization
    <a name="20038"></a>function, Ns_PgServerInit, adds the "ns_pg" Tcl command to the server's
    <a name="20039"></a>Tcl interpreters which can be used to fetch information about an active
    <a name="20040"></a>Postgres95 connection in a Tcl script.
    <a name="20041"></a>
    <a name="20042"></a>*/
    <a name="20043"></a>
    <a name="20044"></a>
    <a name="20045"></a>#define DRIVER_NAME             "Postgres95"
    <a name="20046"></a>
    <a name="20047"></a>static char    *Ns_PgName(Ns_DbHandle *handle);
    <a name="20048"></a>static int      Ns_PgOpenDb(Ns_DbHandle *dbhandle);
    <a name="20049"></a>static int      Ns_PgCloseDb(Ns_DbHandle *dbhandle);
    <a name="20050"></a>static int      Ns_PgCmd(Ns_DbHandle *handle, char *sql);
    <a name="20051"></a>static int      Ns_PgReconnect(Ns_DbHandle *handle);
    <a name="20052"></a>static Ns_Set  *Ns_PgSelect(Ns_DbHandle *handle, char *sql);
    <a name="20053"></a>static int      Ns_PgGetRow(Ns_DbHandle *handle, Ns_Set *row);
    <a name="20054"></a>static int      Ns_PgFlush(Ns_DbHandle *handle);
    <a name="20055"></a>static Ns_DbTableInfo *Ns_PgGetTableInfo(Ns_DbHandle *handle, char *table);
    <a name="20056"></a>static char    *Ns_PgTableList(Ns_DString *pds, Ns_DbHandle *handle, 
    <a name="20057"></a> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;int includesystem);
    <a name="20058"></a>static char    *Ns_PgBestRowId(Ns_DString *pds, Ns_DbHandle *handle, char *table);
    <a name="20059"></a>static int	  &nbsp; &nbsp;Ns_PgServerInit(char *hServer, char *hModule, char *hDriver);
    <a name="20060"></a>static char    *pgName = DRIVER_NAME;
    <a name="20061"></a>static unsigned int	pgCNum = 0;
    <a name="20062"></a>
    <a name="20063"></a>
    <a name="20064"></a>/*-
    <a name="20065"></a> * 
    <a name="20066"></a> * The NULL-terminated PgProcs[] array of Ns_DbProc structures is the
    <a name="20067"></a> * method by which the function pointers are passed to the nsdb module
    <a name="20068"></a> * through the Ns_DbRegisterDriver() function.  Each Ns_DbProc includes
    <a name="20069"></a> * the function id (i.e., DbFn_OpenDb, DbFn_CloseDb, etc.) and the
    <a name="20070"></a> * cooresponding driver function pointer (i.e., Ns_PgOpendb, Ns_PgCloseDb,
    <a name="20071"></a> * etc.).  See nsdb.h for a complete list of function ids.
    <a name="20072"></a> */
    <a name="20073"></a>static Ns_DbProc PgProcs[] = {
    <a name="20074"></a>    {DbFn_Name, (void *) Ns_PgName},
    <a name="20075"></a>    {DbFn_OpenDb, (void *) Ns_PgOpenDb},
    <a name="20076"></a>    {DbFn_CloseDb, (void *) Ns_PgCloseDb},
    <a name="20077"></a>    {DbFn_DML, (void *) Ns_PgCmd},
    <a name="20078"></a>    {DbFn_Select, (void *) Ns_PgSelect},
    <a name="20079"></a>    {DbFn_GetRow, (void *) Ns_PgGetRow},
    <a name="20080"></a>    {DbFn_Flush, (void *) Ns_PgFlush},
    <a name="20081"></a>    {DbFn_Cancel, (void *) Ns_PgFlush},
    <a name="20082"></a>    {DbFn_GetTableInfo, (void *) Ns_PgGetTableInfo},
    <a name="20083"></a>    {DbFn_TableList, (void *) Ns_PgTableList},
    <a name="20084"></a>    {DbFn_BestRowId, (void *) Ns_PgBestRowId},
    <a name="20085"></a>    {DbFn_ServerInit, (void *) Ns_PgServerInit},
    <a name="20086"></a>    {0, NULL}
    <a name="20087"></a>};
    <a name="20088"></a>
    <a name="20089"></a>
    <a name="20090"></a>/*
    <a name="20091"></a> * The NsPgConn structure is connection data specific
    <a name="20092"></a> * to Postgres95. 
    <a name="20093"></a> */ 
    <a name="20094"></a>typedef struct NsPgConn {
    <a name="20095"></a>    PGconn         *conn;
    <a name="20096"></a>    unsigned int    cNum;
    <a name="20097"></a>    PGresult       *res;
    <a name="20098"></a>    int             nCols;
    <a name="20099"></a>    int             nTuples;
    <a name="20100"></a>    int             curTuple;
    <a name="20101"></a>}               NsPgConn;
    <a name="20102"></a>
    <a name="20103"></a>
    <a name="20104"></a>DllExport int   Ns_ModuleVersion = 1;
    <a name="20105"></a>
    <a name="20106"></a>DllExport int
    <a name="20107"></a>Ns_DbDriverInit(char *hDriver, char *configPath)
    <a name="20108"></a>{
    <a name="20109"></a>    /* 
    <a name="20110"></a>     * Register the Postgres95 driver functions with nsdb.
    <a name="20111"></a>     * Nsdb will later call the Ns_PgServerInit() function
    <a name="20112"></a>     * for each virtual server which utilizes nsdb. 
    <a name="20113"></a>     */
    <a name="20115"></a>    if (Ns_DbRegisterDriver(hDriver, &amp;(PgProcs[0])) != NS_OK) {
    <a name="20117"></a>        Ns_Log(Error, "Ns_DbDriverInit(%s):  Could not register the %s driver.",
    <a name="20118"></a>            hDriver, pgName);
    <a name="20119"></a>        return NS_ERROR;
    <a name="20120"></a>    }
    <a name="20121"></a>    Ns_Log(Notice, "%s loaded.", pgName);
    <a name="20122"></a>    return NS_OK;
    <a name="20123"></a>}
    <a name="20124"></a>
    <a name="20125"></a>
    <a name="20126"></a>/*
    <a name="20127"></a> * Ns_PgName - Return the string name which identifies the Postgres95 driver.
    <a name="20128"></a> */
    <a name="20129"></a>static char    *
    <a name="20130"></a>Ns_PgName(Ns_DbHandle *ignored)
    <a name="20131"></a>{
    <a name="20132"></a>    return pgName;
    <a name="20133"></a>}
    <a name="20134"></a>
    <a name="20135"></a>
    <a name="20136"></a>
    <a name="20137"></a>
    <a name="20138"></a>
    <a name="20139"></a>/*
    <a name="20140"></a> * Ns_PgOpenDb - Open an Postgres95 connection on an nsdb handle. The
    <a name="20141"></a> * datasource for Postgres95 is in the form "host:port:database".
    <a name="20142"></a> */
    <a name="20143"></a>static int
    <a name="20144"></a>Ns_PgOpenDb(Ns_DbHandle *handle)
    <a name="20145"></a>{
    <a name="20146"></a>    NsPgConn       *nsConn;
    <a name="20147"></a>    PGconn         *pgConn;
    <a name="20148"></a>    char           *host;
    <a name="20149"></a>    char           *port;
    <a name="20150"></a>    char           *db;
    <a name="20151"></a>    int             status;
    <a name="20152"></a>
    <a name="20153"></a>    assert(handle != NULL);
    <a name="20154"></a>
    <a name="20155"></a>    status = NS_ERROR;
    <a name="20156"></a>    host = handle-&gt;datasource;
    <a name="20157"></a>    port = strchr(handle-&gt;datasource, `:');
    <a name="20158"></a>    if (port == NULL || ((db = strchr(port + 1, `:')) == NULL)) {
    <a name="20159"></a>        Ns_Log(Error, "Ns_PgOpenDb(%s):  Malformed datasource:  %s",
    <a name="20160"></a>	    handle-&gt;driver, handle-&gt;datasource);
    <a name="20161"></a>    } else {
    <a name="20162"></a>        *port++ = `\0';
    <a name="20163"></a>        *db++ = `\0';
    <a name="20164"></a>        Ns_Log(Notice, "Opening %s on %s, %s", db, host, port);
    <a name="20165"></a>        pgConn = PQsetdb(host, port, NULL, NULL, db);
    <a name="20166"></a>        *--db = `:';
    <a name="20167"></a>        *--port = `:';
    <a name="20168"></a>        if (PQstatus(pgConn) == CONNECTION_OK) {
    <a name="20170"></a>            Ns_Log(Notice, "Ns_PgOpenDb(%s):  Openned connection to %s.",
    <a name="20171"></a>		handle-&gt;driver, handle-&gt;datasource);
    <a name="20173"></a>            nsConn = ns_malloc(sizeof(NsPgConn));
    <a name="20174"></a>	    nsConn-&gt;cNum = pgCNum++;
    <a name="20175"></a>            nsConn-&gt;conn = pgConn;
    <a name="20176"></a>            nsConn-&gt;res = NULL;
    <a name="20177"></a>            nsConn-&gt;nCols = nsConn-&gt;nTuples = nsConn-&gt;curTuple = 0;
    <a name="20178"></a>            handle-&gt;connection = nsConn;
    <a name="20179"></a>            status = NS_OK;
    <a name="20180"></a>        } else {
    <a name="20181"></a>            Ns_Log(Error, "Ns_PgOpenDb(%s):  Could not connect to %s:  %s", 
    <a name="20182"></a> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;handle-&gt;driver, handle-&gt;datasource, PQerrorMessage(pgConn));
    <a name="20183"></a>            PQfinish(pgConn);
    <a name="20184"></a>	    return NS_ERROR;
    <a name="20185"></a>        }
    <a name="20186"></a>    }
    <a name="20187"></a>    return NS_OK;
    <a name="20188"></a>}
    <a name="20189"></a>
    <a name="20190"></a>
    <a name="20191"></a>/*
    <a name="20192"></a> * Ns_PgCloseDb - Close an Postgres95 connection on an nsdb handle.
    <a name="20193"></a> */
    <a name="20194"></a>static int
    <a name="20195"></a>Ns_PgCloseDb(Ns_DbHandle *handle)
    <a name="20196"></a>{
    <a name="20197"></a>    NsPgConn       *nsConn;
    <a name="20198"></a>
    <a name="20199"></a>    assert(handle != NULL);
    <a name="20200"></a>
    <a name="20201"></a>    nsConn = handle-&gt;connection;
    <a name="20202"></a>    if (handle-&gt;verbose) {
    <a name="20203"></a>	Ns_Log(Notice, "Ns_PgCloseDb(%d):  Closing connection:  %s",
    <a name="20204"></a>	    nsConn-&gt;cNum, handle-&gt;datasource);
    <a name="20205"></a>    }
    <a name="20206"></a>    PQfinish(nsConn-&gt;conn);
    <a name="20207"></a>    nsConn-&gt;conn = NULL;
    <a name="20208"></a>    nsConn-&gt;nCols = nsConn-&gt;nTuples = nsConn-&gt;curTuple = 0;
    <a name="20210"></a>    ns_free(nsConn);
    <a name="20211"></a>    handle-&gt;connection = NULL;
    <a name="20212"></a>    return NS_OK;
    <a name="20213"></a>}
    <a name="20214"></a>
    <a name="20215"></a>
    <a name="20216"></a>/*
    <a name="20217"></a> * Ns_PgExec - Send a Postgres95 query.  This function does not
    <a name="20218"></a> * implement an nsdb function but is used internally by the Postgres95
    <a name="20219"></a> * driver.
    <a name="20220"></a> */
    <a name="20221"></a>static int
    <a name="20222"></a>Ns_PgExec(Ns_DbHandle *handle, char *sql)
    <a name="20223"></a>{
    <a name="20224"></a>    NsPgConn       *nsConn;
    <a name="20225"></a>    Ns_DString      dsSql;
    <a name="20226"></a>    int             status;
    <a name="20227"></a>
    <a name="20228"></a>    assert(handle != NULL);
    <a name="20229"></a>    assert(sql != NULL);
    <a name="20230"></a>
    <a name="20231"></a>    status = NS_ERROR;
    <a name="20232"></a>    nsConn = handle-&gt;connection;
    <a name="20234"></a>    Ns_DStringInit(&amp;dsSql);
    <a name="20236"></a>    Ns_DStringAppend(&amp;dsSql, sql);
    <a name="20237"></a>    while (dsSql.length &gt; 0 &amp;&amp; isspace(dsSql.string[dsSql.length - 1])) {
    <a name="20238"></a>        dsSql.string[--dsSql.length] = `\0';
    <a name="20239"></a>    }
    <a name="20240"></a>    if (dsSql.length &gt; 0 &amp;&amp; dsSql.string[dsSql.length - 1] != `;') {
    <a name="20242"></a>        Ns_DStringNAppend(&amp;dsSql, ";", 1);
    <a name="20243"></a>    }
    <a name="20244"></a>    nsConn-&gt;res = PQexec(nsConn-&gt;conn, dsSql.string);
    <a name="20246"></a>    Ns_DStringFree(&amp;dsSql);
    <a name="20247"></a>    if (nsConn-&gt;res == NULL) {
    <a name="20249"></a>        Ns_Log(Error, "Ns_PgExec(%s):  Could not send query `%s':  %s",
    <a name="20250"></a>            handle-&gt;datasource, sql, PQerrorMessage(nsConn-&gt;conn));
    <a name="20251"></a>        return NS_ERROR;
    <a name="20252"></a>    }
    <a name="20253"></a>    return NS_OK;
    <a name="20254"></a>}
    <a name="20255"></a>
    <a name="20256"></a>
    <a name="20257"></a>/*
    <a name="20258"></a> * Ns_PgCmd - Send a query which should return a command result.
    <a name="20259"></a> */
    <a name="20260"></a>static int
    <a name="20261"></a>Ns_PgCmd(Ns_DbHandle *handle, char *sql)
    <a name="20262"></a>{
    <a name="20263"></a>    int             status;
    <a name="20264"></a>    NsPgConn       *nsConn;
    <a name="20265"></a>
    <a name="20266"></a>    assert(handle != NULL);
    <a name="20267"></a>    assert(sql != NULL);
    <a name="20268"></a>
    <a name="20269"></a>    nsConn = handle-&gt;connection;
    <a name="20270"></a>    status = Ns_PgExec(handle, sql);
    <a name="20271"></a>    if (status == NS_OK) {
    <a name="20272"></a>        if (PQresultStatus(nsConn-&gt;res) != PGRES_COMMAND_OK) {
    <a name="20273"></a>            Ns_Log(Error, 
    <a name="20274"></a> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;"Ns_PgCmd(%s):  Query `%s' did not return PGRES_COMMAND_OK status.",
    <a name="20275"></a>                handle-&gt;datasource, sql);
    <a name="20276"></a>            status = NS_ERROR;
    <a name="20277"></a>        }
    <a name="20278"></a>	nsConn-&gt;nCols = 0;
    <a name="20279"></a>        PQclear(nsConn-&gt;res);
    <a name="20280"></a>	nsConn-&gt;res = NULL;
    <a name="20281"></a>    }
    <a name="20282"></a>    return status;
    <a name="20283"></a>}
    <a name="20284"></a>
    <a name="20285"></a>
    <a name="20286"></a>
    <a name="20287"></a>/*
    <a name="20288"></a> * Ns_PgSelect - Send a query which should return rows.
    <a name="20289"></a> */
    <a name="20290"></a>static Ns_Set  *
    <a name="20291"></a>Ns_PgSelect(Ns_DbHandle *handle, char *sql)
    <a name="20292"></a>{
    <a name="20293"></a>    Ns_Set         *row;
    <a name="20294"></a>    NsPgConn       *nsConn;
    <a name="20295"></a>    int             i;
    <a name="20296"></a>
    <a name="20297"></a>    assert(handle != NULL);
    <a name="20298"></a>    assert(sql != NULL);
    <a name="20299"></a>
    <a name="20300"></a>    row = NULL;
    <a name="20301"></a>    nsConn = handle-&gt;connection;
    <a name="20302"></a>    if (Ns_PgExec(handle, sql) == NS_OK) {
    <a name="20303"></a>	if (PQresultStatus(nsConn-&gt;res) == PGRES_TUPLES_OK) {
    <a name="20304"></a>            nsConn-&gt;curTuple = 0;
    <a name="20305"></a>            nsConn-&gt;nCols = PQnfields(nsConn-&gt;res);
    <a name="20306"></a>            nsConn-&gt;nTuples = PQntuples(nsConn-&gt;res);
    <a name="20307"></a>	    row = handle-&gt;row;
    <a name="20308"></a>            for (i = 0; i &lt; nsConn-&gt;nCols; ++i) {
    <a name="20310"></a>                Ns_SetPut(row, PQfname(nsConn-&gt;res, i), NULL);
    <a name="20311"></a>            }
    <a name="20312"></a>        } else {
    <a name="20313"></a>	    Ns_Log(Error, "Ns_PgSelect(%s):  Query did not return rows:  %s",
    <a name="20314"></a>		handle-&gt;datasource, sql);
    <a name="20315"></a>	}
    <a name="20316"></a>    }
    <a name="20317"></a>    return row;
    <a name="20318"></a>}
    <a name="20319"></a>
    <a name="20320"></a>
    <a name="20321"></a>/*
    <a name="20322"></a> * Ns_PgGetRow - Fetch rows after an Ns_PgSelect.
    <a name="20323"></a> */
    <a name="20324"></a>static int
    <a name="20325"></a>Ns_PgGetRow(Ns_DbHandle *handle, Ns_Set *row)
    <a name="20326"></a>{
    <a name="20327"></a>    NsPgConn       *nsConn;
    <a name="20328"></a>    int             status;
    <a name="20329"></a>    int             i;
    <a name="20330"></a>
    <a name="20331"></a>    assert(handle != NULL);
    <a name="20332"></a>    assert(row != NULL);
    <a name="20333"></a>    assert(handle-&gt;connection != NULL);
    <a name="20334"></a>
    <a name="20335"></a>    nsConn = handle-&gt;connection;
    <a name="20336"></a>    if (nsConn-&gt;nCols == 0) {
    <a name="20337"></a>        Ns_Log(Error, "Ns_PgGetRow(%s):  Get row called outside a fetch row loop.",
    <a name="20338"></a>	    handle-&gt;datasource);
    <a name="20339"></a>        status = NS_ERROR;
    <a name="20340"></a>    } else if (nsConn-&gt;curTuple == nsConn-&gt;nTuples) {
    <a name="20341"></a>        PQclear(nsConn-&gt;res);
    <a name="20342"></a>	nsConn-&gt;res = NULL;
    <a name="20343"></a>        nsConn-&gt;nCols = nsConn-&gt;nTuples = nsConn-&gt;curTuple = 0;
    <a name="20344"></a>        status = NS_END_DATA;
    <a name="20345"></a>    } else {
    <a name="20346"></a>        for (i = 0; i &lt; nsConn-&gt;nCols; i++) {
    <a name="20348"></a>            Ns_SetPutValue(row, (int) i, PQgetvalue(nsConn-&gt;res, 
    <a name="20349"></a> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;nsConn-&gt;curTuple, i));
    <a name="20350"></a>        }
    <a name="20351"></a>        ++nsConn-&gt;curTuple;
    <a name="20352"></a>        return NS_OK;
    <a name="20353"></a>    }
    <a name="20354"></a>    return status;
    <a name="20355"></a>}
    <a name="20356"></a>
    <a name="20357"></a>
    <a name="20358"></a>/*
    <a name="20359"></a> * Ns_PgFlush - Flush any waiting rows not needed after an Ns_DbSelect().
    <a name="20360"></a> */
    <a name="20361"></a>static int
    <a name="20362"></a>Ns_PgFlush(Ns_DbHandle *handle)
    <a name="20363"></a>{
    <a name="20364"></a>    NsPgConn       *nsConn;
    <a name="20365"></a>
    <a name="20366"></a>    assert(handle != NULL);
    <a name="20367"></a>    assert(handle-&gt;connection != NULL);
    <a name="20368"></a>
    <a name="20369"></a>    nsConn = handle-&gt;connection;
    <a name="20370"></a>    if (nsConn-&gt;nCols &gt; 0) {
    <a name="20371"></a>        PQclear(nsConn-&gt;res);
    <a name="20372"></a>	nsConn-&gt;res = NULL;
    <a name="20373"></a>        nsConn-&gt;nCols = nsConn-&gt;nTuples = nsConn-&gt;curTuple = 0;
    <a name="20374"></a>    }
    <a name="20375"></a>    return NS_OK;
    <a name="20376"></a>}
    <a name="20377"></a>
    <a name="20378"></a>
    <a name="20379"></a>/*
    <a name="20380"></a> * Ns_DbTableInfo - Return system catalog information (columns, types, etc.)
    <a name="20381"></a> * about a table.
    <a name="20382"></a> */
    <a name="20383"></a>static Ns_DbTableInfo *
    <a name="20384"></a>Ns_PgGetTableInfo(Ns_DbHandle *handle, char *table)
    <a name="20385"></a>{
    <a name="20386"></a>    Ns_Set         *row;
    <a name="20387"></a>    Ns_Set         *col;
    <a name="20388"></a>    Ns_DString      ds;
    <a name="20389"></a>    Ns_DbTableInfo *tinfo;
    <a name="20390"></a>    int             status;
    <a name="20391"></a>    char           *name;
    <a name="20392"></a>    char           *type;
    <a name="20393"></a>
    <a name="20394"></a>
    <a name="20396"></a>    Ns_DStringInit(&amp;ds);
    <a name="20398"></a>    Ns_DStringVarAppend(&amp;ds, "SELECT a.attname, t.typname "
    <a name="20399"></a>        "FROM pg_class c, pg_attribute a, pg_type t "
    <a name="20400"></a>        "WHERE c.relname = `", table, "` "
    <a name="20401"></a>        "and a.attnum &gt; 0 and a.attrelid = c.oid "
    <a name="20402"></a>        "and a.atttypid = t.oid ORDER BY attname", NULL);
    <a name="20403"></a>
    <a name="20405"></a>    row = Ns_DbSelect(handle, ds.string);
    <a name="20407"></a>    Ns_DStringFree(&amp;ds);
    <a name="20408"></a>    tinfo = NULL;
    <a name="20409"></a>    if (row != NULL) {
    <a name="20410"></a>        while ((status = Ns_PgGetRow(handle, row)) == NS_OK) {
    <a name="20411"></a>            name = row-&gt;fields[0].value;
    <a name="20412"></a>            type = row-&gt;fields[1].value;
    <a name="20413"></a>            if (name == NULL || type == NULL) {
    <a name="20414"></a>                Ns_Log(Error, 
    <a name="20415"></a> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;"Ns_PgGetTableInfo(%s):  Invalid `pg_attribute' entry for table:  %s",
    <a name="20416"></a>                    handle-&gt;datasource, table);
    <a name="20417"></a>                break;
    <a name="20418"></a>            }
    <a name="20419"></a>
    <a name="20420"></a>            /*
    <a name="20421"></a>             * NB:  Move the fields directly from the row
    <a name="20422"></a>	     * Ns_Set to the col Ns_Set to avoid a data copy.
    <a name="20423"></a>             */
    <a name="20425"></a>            col = Ns_SetCreate(NULL);
    <a name="20426"></a>            col-&gt;name = name;
    <a name="20428"></a>            Ns_SetPut(col, "type", NULL);
    <a name="20429"></a>            col-&gt;fields[0].value = type;
    <a name="20430"></a>            row-&gt;fields[0].value = NULL;
    <a name="20431"></a>            row-&gt;fields[1].value = NULL;
    <a name="20432"></a>            if (tinfo == NULL) {
    <a name="20434"></a>                tinfo = Ns_DbNewTableInfo(table);
    <a name="20435"></a>            }
    <a name="20437"></a>            Ns_DbAddColumnInfo(tinfo, col);
    <a name="20438"></a>        }
    <a name="20439"></a>        if (status != NS_END_DATA &amp;&amp; tinfo != NULL) {
    <a name="20441"></a>            Ns_DbFreeTableInfo(tinfo);
    <a name="20442"></a>            tinfo = NULL;
    <a name="20443"></a>        }
    <a name="20444"></a>    }
    <a name="20445"></a>    return tinfo;
    <a name="20446"></a>}
    <a name="20447"></a>
    <a name="20448"></a>
    <a name="20449"></a>
    <a name="20450"></a>
    <a name="20451"></a>
    <a name="20452"></a>/*
    <a name="20453"></a> * Ns_PgTableList - Return a list of tables in the database.
    <a name="20454"></a> */ 
    <a name="20455"></a>static char    *
    <a name="20456"></a>Ns_PgTableList(Ns_DString *pds, Ns_DbHandle *handle, int fSystemTables)
    <a name="20457"></a>{
    <a name="20458"></a>    Ns_Set         *row;
    <a name="20459"></a>    Ns_DString      ds;
    <a name="20460"></a>    char           *table;
    <a name="20461"></a>    int             status;
    <a name="20462"></a>
    <a name="20464"></a>    Ns_DStringInit(&amp;ds);
    <a name="20466"></a>    Ns_DStringAppend(&amp;ds, "SELECT relname FROM pg_class "
    <a name="20467"></a>        "WHERE relkind = `r' and relname !~ `^Inv' ");
    <a name="20468"></a>    if (!fSystemTables) {
    <a name="20469"></a>        Ns_DStringAppend(&amp;ds, "and relname !~ `^pg_' ");
    <a name="20470"></a>    }
    <a name="20471"></a>    Ns_DStringAppend(&amp;ds, "ORDER BY relname");
    <a name="20473"></a>    row = Ns_DbSelect(handle, ds.string);
    <a name="20474"></a>    Ns_DStringFree(&amp;ds);
    <a name="20475"></a>    status = NS_ERROR;
    <a name="20476"></a>    if (row != NULL) {
    <a name="20478"></a>        while ((status = Ns_DbGetRow(handle, row)) == NS_OK) {
    <a name="20479"></a>            table = row-&gt;fields[0].value;
    <a name="20480"></a>            if (table == NULL) {
    <a name="20482"></a>                Ns_Log(Warning, 
    <a name="20483"></a> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;"Ns_PgTableList(%s):  NULL relname in `pg_class' table.",
    <a name="20484"></a>		     handle-&gt;datasource);
    <a name="20485"></a>            } else {
    <a name="20486"></a>                Ns_DStringNAppend(pds, table, strlen(table) + 1);
    <a name="20487"></a>            }
    <a name="20488"></a>        }
    <a name="20489"></a>    }
    <a name="20490"></a>    if (status == NS_END_DATA) {
    <a name="20491"></a>        return pds-&gt;string;
    <a name="20492"></a>    }
    <a name="20493"></a>    return NULL;
    <a name="20494"></a>}
    <a name="20495"></a>
    <a name="20496"></a>
    <a name="20497"></a>/*
    <a name="20498"></a> * Ns_PgBestRowId - Return the primary key of a table.  If a table
    <a name="20502"></a> * has a primary key, the AOLserver can perform row updates and
    <a name="20503"></a> * deletes.  In the case of Postgres95, the "oid" system column is alwasy
    <a name="20504"></a> * unique so we just return it instead of looking for an actual
    <a name="20505"></a> * primary key.
    <a name="20506"></a> */
    <a name="20507"></a>static char    *
    <a name="20508"></a>Ns_PgBestRowId(Ns_DString *pds, Ns_DbHandle *handle, char *table)
    <a name="20509"></a>{
    <a name="20511"></a>    Ns_DStringNAppend(pds, "oid", 4);
    <a name="20512"></a>    return pds-&gt;string;
    <a name="20513"></a>}
    <a name="20514"></a>
    <a name="20515"></a>
    <a name="20516"></a>
    <a name="20517"></a>/*
    <a name="20518"></a> * PgCmd - This function implements the "ns_pg" Tcl command installed into
    <a name="20519"></a> * each interpreter of each virtual server.  It provides access to features
    <a name="20520"></a> * specific to the Postgres95 driver.
    <a name="20521"></a> */
    <a name="20522"></a>static int
    <a name="20523"></a>PgCmd(ClientData dummy, Tcl_Interp *interp, int argc, char **argv)
    <a name="20524"></a>{
    <a name="20525"></a>    Ns_DbHandle    *handle;
    <a name="20526"></a>    NsPgConn        *pgconn;
    <a name="20527"></a>
    <a name="20528"></a>    if (argc != 3) {
    <a name="20530"></a>        Tcl_AppendResult(interp, "wrong # args: should be \"",
    <a name="20531"></a>            argv[0], " command dbId\"", NULL);
    <a name="20532"></a>        return TCL_ERROR;
    <a name="20533"></a>    }
    <a name="20535"></a>    if (Ns_TclDbGetHandle(interp, argv[2], &amp;handle) != TCL_OK) {
    <a name="20536"></a>        return TCL_ERROR;
    <a name="20537"></a>    }
    <a name="20538"></a>
    <a name="20539"></a>    /*
    <a name="20540"></a>     * Make sure this is a Postgres95 handle before accessing
    <a name="20541"></a>     * handle-&gt;connection as an NsPgConn.
    <a name="20542"></a>     */
    <a name="20544"></a>    if (Ns_DbDriverName(handle) != pgName) {
    <a name="20546"></a>        Tcl_AppendResult(interp, "handle \"", argv[1], "\" is not of type \"",
    <a name="20547"></a>            pgName, "\"", NULL);
    <a name="20548"></a>        return TCL_ERROR;
    <a name="20549"></a>    }
    <a name="20550"></a>    pgconn = (NsPgConn *) handle-&gt;connection;
    <a name="20551"></a>    if (!strcmp(argv[1], "db")) {
    <a name="20553"></a>	Tcl_SetResult(interp, PQdb(pgconn-&gt;conn), TCL_STATIC);
    <a name="20554"></a>    } else if (!strcmp(argv[1], "host")) {
    <a name="20555"></a>	Tcl_SetResult(interp, PQhost(pgconn-&gt;conn), TCL_STATIC);
    <a name="20556"></a>    } else if (!strcmp(argv[1], "options")) {
    <a name="20557"></a>	Tcl_SetResult(interp, PQoptions(pgconn-&gt;conn), TCL_STATIC);
    <a name="20558"></a>    } else if (!strcmp(argv[1], "port")) {
    <a name="20559"></a>	Tcl_SetResult(interp, PQport(pgconn-&gt;conn), TCL_STATIC);
    <a name="20560"></a>    } else if (!strcmp(argv[1], "number")) {
    <a name="20561"></a>	sprintf(interp-&gt;result, "%u", pgconn-&gt;cNum);
    <a name="20562"></a>    } else if (!strcmp(argv[1], "error")) {
    <a name="20563"></a>	Tcl_SetResult(interp, PQerrorMessage(pgconn-&gt;conn), TCL_STATIC);
    <a name="20564"></a>    } else if (!strcmp(argv[1], "status")) {
    <a name="20565"></a>	if (PQstatus(pgconn-&gt;conn) == CONNECTION_OK) {
    <a name="20566"></a>	    interp-&gt;result = "ok";
    <a name="20567"></a>	} else {
    <a name="20568"></a>	    interp-&gt;result = "bad";
    <a name="20569"></a>	}
    <a name="20570"></a>    } else {
    <a name="20572"></a>        Tcl_AppendResult(interp, "unknown command \"", argv[2],
    <a name="20573"></a>            "\": should be db, host, options, port, error or status.", NULL);
    <a name="20574"></a>        return TCL_ERROR;
    <a name="20575"></a>    }
    <a name="20576"></a>    return TCL_OK;
    <a name="20577"></a>}
    <a name="20578"></a>
    <a name="20579"></a>
    <a name="20580"></a>/*
    <a name="20581"></a> * Ns_PgInterpInit - Add the "ns_pg" command to a single Tcl interpreter.
    <a name="20582"></a> */
    <a name="20583"></a>static int
    <a name="20584"></a>Ns_PgInterpInit(Tcl_Interp *interp, void *ignored)
    <a name="20585"></a>{
    <a name="20587"></a>    Tcl_CreateCommand(interp, "ns_pg", PgCmd, NULL, NULL);
    <a name="20588"></a>    return NS_OK;
    <a name="20589"></a>}
    <a name="20590"></a>
    <a name="20591"></a>
    <a name="20592"></a>/*
    <a name="20593"></a> * Ns_PgServerInit - Have Ns_PgInterpInit called for each interpreter in
    <a name="20594"></a> * the virtual server which is being intialized.
    <a name="20595"></a> */
    <a name="20596"></a>static int
    <a name="20597"></a>Ns_PgServerInit(char *hServer, char *hModule, char *hDriver)
    <a name="20598"></a>{
    <a name="20600"></a>    return Ns_TclInitInterps(hServer, Ns_PgInterpInit, NULL);
    <a name="20601"></a>}
    <a name="17669"></a>
</pre><p>

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