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- fixed dblink invalid pointer causing corrupt elog message - fixed dblink_tok improper handling of null results - fixed examples in README.dblink Joe Conway
285 lines
6.7 KiB
C
285 lines
6.7 KiB
C
/*
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* dblink.c
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*
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* Functions returning results from a remote database
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*
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* Copyright (c) Joseph Conway <joe.conway@mail.com>, 2001;
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*
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* Permission to use, copy, modify, and distribute this software and its
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* documentation for any purpose, without fee, and without a written agreement
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* is hereby granted, provided that the above copyright notice and this
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* paragraph and the following two paragraphs appear in all copies.
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*
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* IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
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* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
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* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIMS ANY WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
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* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
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*
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*/
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#include "dblink.h"
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PG_FUNCTION_INFO_V1(dblink);
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Datum
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dblink(PG_FUNCTION_ARGS)
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{
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PGconn *conn = NULL;
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PGresult *res = NULL;
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dblink_results *results;
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char *optstr;
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char *sqlstatement;
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char *curstr = "DECLARE mycursor CURSOR FOR ";
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char *execstatement;
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char *msg;
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int ntuples = 0;
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ReturnSetInfo *rsi;
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if (PG_ARGISNULL(0) || PG_ARGISNULL(1)) {
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elog(ERROR, "dblink: NULL arguments are not permitted");
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}
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if (fcinfo->resultinfo == NULL || ! IsA(fcinfo->resultinfo, ReturnSetInfo)) {
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elog(ERROR, "dblink: function called in context that does not accept a set result");
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}
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optstr = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0))));
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sqlstatement = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(1))));
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if (fcinfo->flinfo->fn_extra == NULL) {
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conn = PQconnectdb(optstr);
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if (PQstatus(conn) == CONNECTION_BAD)
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{
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msg = pstrdup(PQerrorMessage(conn));
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PQfinish(conn);
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elog(ERROR, "dblink: connection error: %s", msg);
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}
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res = PQexec(conn, "BEGIN");
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if (PQresultStatus(res) != PGRES_COMMAND_OK)
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{
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msg = pstrdup(PQerrorMessage(conn));
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PQclear(res);
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PQfinish(conn);
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elog(ERROR, "dblink: begin error: %s", msg);
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}
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PQclear(res);
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execstatement = (char *) palloc(strlen(curstr) + strlen(sqlstatement) + 1);
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if (execstatement != NULL) {
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strcpy(execstatement, curstr);
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strcat(execstatement, sqlstatement);
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strcat(execstatement, "\0");
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} else {
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elog(ERROR, "dblink: insufficient memory" );
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}
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res = PQexec(conn, execstatement);
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if (!res || (PQresultStatus(res) != PGRES_COMMAND_OK && PQresultStatus(res) != PGRES_TUPLES_OK))
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{
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msg = pstrdup(PQerrorMessage(conn));
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PQclear(res);
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PQfinish(conn);
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elog(ERROR, "dblink: sql error: %s", msg);
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} else {
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/*
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* got results, start fetching them
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*/
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PQclear(res);
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res = PQexec(conn, "FETCH ALL in mycursor");
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if (!res || PQresultStatus(res) != PGRES_TUPLES_OK) {
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msg = pstrdup(PQerrorMessage(conn));
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PQclear(res);
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PQfinish(conn);
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elog(ERROR, "dblink: sql error: %s", msg);
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}
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ntuples = PQntuples(res);
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if (ntuples > 0) {
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results = init_dblink_results(fcinfo->flinfo->fn_mcxt);
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results->tup_num = 0;
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results->res = res;
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res = NULL;
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(dblink_results *) fcinfo->flinfo->fn_extra = results;
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results = NULL;
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results = fcinfo->flinfo->fn_extra;
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/* close the cursor */
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res = PQexec(conn, "CLOSE mycursor");
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PQclear(res);
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/* commit the transaction */
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res = PQexec(conn, "COMMIT");
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PQclear(res);
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/* close the connection to the database and cleanup */
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PQfinish(conn);
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rsi = (ReturnSetInfo *)fcinfo->resultinfo;
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rsi->isDone = ExprMultipleResult;
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PG_RETURN_POINTER(results);
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} else {
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PQclear(res);
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/* close the cursor */
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res = PQexec(conn, "CLOSE mycursor");
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PQclear(res);
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/* commit the transaction */
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res = PQexec(conn, "COMMIT");
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PQclear(res);
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/* close the connection to the database and cleanup */
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PQfinish(conn);
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rsi = (ReturnSetInfo *)fcinfo->resultinfo;
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rsi->isDone = ExprEndResult ;
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PG_RETURN_NULL();
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}
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}
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} else {
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/*
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* check for more results
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*/
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results = fcinfo->flinfo->fn_extra;
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results->tup_num++;
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ntuples = PQntuples(results->res);
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if (results->tup_num < ntuples) {
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/*
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* fetch them if available
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*/
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rsi = (ReturnSetInfo *)fcinfo->resultinfo;
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rsi->isDone = ExprMultipleResult;
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PG_RETURN_POINTER(results);
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} else {
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/*
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* or if no more, clean things up
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*/
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results = fcinfo->flinfo->fn_extra;
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PQclear(results->res);
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rsi = (ReturnSetInfo *)fcinfo->resultinfo;
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rsi->isDone = ExprEndResult ;
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PG_RETURN_NULL();
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}
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}
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PG_RETURN_NULL();
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}
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/*
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* dblink_tok
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* parse dblink output string
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* return fldnum item (0 based)
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* based on provided field separator
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*/
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PG_FUNCTION_INFO_V1(dblink_tok);
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Datum
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dblink_tok(PG_FUNCTION_ARGS)
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{
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dblink_results *results;
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int fldnum;
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text *result_text;
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char *result;
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int nfields = 0;
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int text_len = 0;
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if (PG_ARGISNULL(0) || PG_ARGISNULL(1)) {
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elog(ERROR, "dblink: NULL arguments are not permitted");
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}
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results = (dblink_results *) PG_GETARG_POINTER(0);
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if (results == NULL) {
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elog(ERROR, "dblink: function called with invalid result pointer");
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}
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fldnum = PG_GETARG_INT32(1);
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if (fldnum < 0) {
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elog(ERROR, "dblink: field number < 0 not permitted");
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}
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nfields = PQnfields(results->res);
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if (fldnum > (nfields - 1)) {
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elog(ERROR, "dblink: field number %d does not exist", fldnum);
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}
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if (PQgetisnull(results->res, results->tup_num, fldnum) == 1) {
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PG_RETURN_NULL();
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} else {
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text_len = PQgetlength(results->res, results->tup_num, fldnum);
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result = (char *) palloc(text_len + 1);
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if (result != NULL) {
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strcpy(result, PQgetvalue(results->res, results->tup_num, fldnum));
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strcat(result, "\0");
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} else {
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elog(ERROR, "dblink: insufficient memory" );
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}
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result_text = DatumGetTextP(DirectFunctionCall1(textin, CStringGetDatum(result)));
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PG_RETURN_TEXT_P(result_text);
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}
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}
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/*
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* internal functions
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*/
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/*
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* init_dblink_results
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* - create an empty dblink_results data structure
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*/
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dblink_results *
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init_dblink_results(MemoryContext fn_mcxt)
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{
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MemoryContext oldcontext;
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dblink_results *retval;
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oldcontext = MemoryContextSwitchTo(fn_mcxt);
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retval = (dblink_results *) palloc(sizeof(dblink_results));
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MemSet(retval, 0, sizeof(dblink_results));
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retval->tup_num = -1;
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retval->res = NULL;
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MemoryContextSwitchTo(oldcontext);
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return retval;
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}
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