/* * testlibpq.c * * Test the C version of libpq,the Postgresql frontend library. */#include <stdio.h>#include <stdlib.h>#include <libpq-fe.h>static voIDexit_nicely(PGconn *conn){ PQfinish(conn); exit(1);}intmain(int argc,char **argv){ const char *conninfo; PGconn *conn; PGresult *res; int nFIElds; int i,j; /* * If the user supplIEs a parameter on the command line,use it as the * conninfo string; otherwise default to setting dbname=postgres and using * environment variables or defaults for all other connection parameters. */ if (argc > 1) conninfo = argv[1]; else conninfo = "dbname = postgres"; /* Make a connection to the database */ conn = PQconnectdb(conninfo); /* Check to see that the backend connection was successfully made */ if (PQstatus(conn) != CONNECTION_OK) { fprintf(stderr,"Connection to database Failed: %s",PQerrorMessage(conn)); exit_nicely(conn); } /* * Our test case here involves using a cursor,for which we must be insIDe * a transaction block. We Could do the whole thing with a single * PQexec() of "select * from pg_database",but that's too trivial to make * a good example. */ /* Start a transaction block */ res = PQexec(conn,"BEGIN"); if (PQresultStatus(res) != PGRES_COMMAND_OK) { fprintf(stderr,"BEGIN command Failed: %s",PQerrorMessage(conn)); PQclear(res); exit_nicely(conn); } /* * Should PQclear PGresult whenever it is no longer needed to avoID memory * leaks */ PQclear(res); /* * Fetch rows from pg_database,the system catalog of databases */ res = PQexec(conn,"DECLARE myportal CURSOR FOR select * from pg_database"); if (PQresultStatus(res) != PGRES_COMMAND_OK) { fprintf(stderr,"DECLARE CURSOR Failed: %s",PQerrorMessage(conn)); PQclear(res); exit_nicely(conn); } PQclear(res); res = PQexec(conn,"FETCH ALL in myportal"); if (PQresultStatus(res) != PGRES_TUPLES_OK) { fprintf(stderr,"FETCH ALL Failed: %s",PQerrorMessage(conn)); PQclear(res); exit_nicely(conn); } /* first,print out the attribute names */ nFIElds = PQnfIElds(res); for (i = 0; i < nFIElds; i++) printf("%-15s",PQfname(res,i)); printf("\n\n"); /* next,print out the rows */ for (i = 0; i < PQntuples(res); i++) { for (j = 0; j < nFIElds; j++) printf("%-15s",PQgetvalue(res,i,j)); printf("\n"); } PQclear(res); /* close the portal ... we don't bother to check for errors ... */ res = PQexec(conn,"CLOSE myportal"); PQclear(res); /* end the transaction */ res = PQexec(conn,"END"); PQclear(res); /* close the connection to the database and cleanup */ PQfinish(conn); return 0;}
/* * testlibpq2.c * Test of the asynchronous notification interface * * Start this program,then from psql in another window do * NOTIFY TBL2; * Repeat four times to get this program to exit. * * Or,if you want to get fancy,try this: * populate a database with the following commands * (provIDed in src/test/examples/testlibpq2.sql): * * CREATE table TBL1 (i int4); * * CREATE table TBL2 (i int4); * * CREATE RulE r1 AS ON INSERT TO TBL1 DO * (INSERT INTO TBL2 VALUES (new.i); NOTIFY TBL2); * * and do this four times: * * INSERT INTO TBL1 VALUES (10); */#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#include <sys/time.h>#include <libpq-fe.h>static voIDexit_nicely(PGconn *conn){ PQfinish(conn); exit(1);}intmain(int argc,char **argv){ const char *conninfo; PGconn *conn; PGresult *res; PGnotify *notify; int nnotifIEs; /* * If the user supplIEs a parameter on the command line,PQerrorMessage(conn)); exit_nicely(conn); } /* * Issue ListEN command to enable notifications from the rule's NOTIFY. */ res = PQexec(conn,"ListEN TBL2"); if (PQresultStatus(res) != PGRES_COMMAND_OK) { fprintf(stderr,"ListEN command Failed: %s",PQerrorMessage(conn)); PQclear(res); exit_nicely(conn); } /* * should PQclear PGresult whenever it is no longer needed to avoID memory * leaks */ PQclear(res); /* Quit after four notifIEs are received. */ nnotifIEs = 0; while (nnotifIEs < 4) { /* * Sleep until something happens on the connection. We use select(2) * to wait for input,but you Could also use poll() or similar * facilitIEs. */ int sock; fd_set input_mask; sock = PQsocket(conn); if (sock < 0) break; /* shouldn't happen */ FD_ZERO(&input_mask); FD_SET(sock,&input_mask); if (select(sock + 1,&input_mask,NulL,NulL) < 0) { fprintf(stderr,"select() Failed: %s\n",strerror(errno)); exit_nicely(conn); } /* Now check for input */ PQconsumeinput(conn); while ((notify = PQnotifIEs(conn)) != NulL) { fprintf(stderr,"ASYNC NOTIFY of '%s' received from backend PID %d\n",notify->relname,notify->be_pID); PQfreemem(notify); nnotifIEs++; } } fprintf(stderr,"Done.\n"); /* close the connection to the database and cleanup */ PQfinish(conn); return 0;}
/* * testlibpq3.c * Test out-of-line parameters and binary I/O. * * Before running this,populate a database with the following commands * (provIDed in src/test/examples/testlibpq3.sql): * * CREATE table test1 (i int4,t text,b bytea); * * INSERT INTO test1 values (1,'joe''s place','\000\001\002\003\004'); * INSERT INTO test1 values (2,'ho there','\004\003\002\001\000'); * * The expected output is: * * tuple 0: got * i = (4 bytes) 1 * t = (11 bytes) 'joe's place' * b = (5 bytes) */0#include 1#include 2#include 3string4 * * tuple 0: got * i = (4 bytes) 2 * t = (8 bytes) 'ho there' * b = (5 bytes) #include 4#include 3/*2 for ntohl/htonl 1*/0 #include in<stdio.h>#include <stdlib.h>static<voID.h>exit_nicely(PGconn <sys/types.h>conn){ PQfinish(conn); exit(<libpq-fe.h>1);}/* * This function prints a query result that is a binary-format fetch from * a table defined as in the comment above. We split it out because the * main() function uses it twice. <netinet/*/.h>static<arpa/inet.h>voID show_binary_results(PGresult res){ *int i,j; int i_fnum,t_fnum,b_fnum; /* Use PQfnumber to avoID assumptions about fIEld order in result */ i_fnum "*i"); t_fnum "t"); b_fnum "b= PQfnumber(res,"); for0= PQfnumber(res,) { chariptr; char= PQfnumber(res,tptr; charbptr; int blen; (i = int; i < PQntuples(res); i++ ival; /* * Get the fIEld values (we ignore possibility they are null!) */ * iptr PQgetvalue(res,i_fnum); tptr * PQgetvalue(res,t_fnum); bptr PQgetvalue(res,b_fnum); /* * The binary representation of INT4 is in network byte order,which * we'd better coerce to the local byte order. */ ival ) iptr)); /* * The binary representation of TEXT is,well,text,and since libpq * was nice enough to append a zero byte to it,it'll work just fine * as a C string. * * The binary representation of BYTEA is a bunch of bytes,which Could * include embedded nulls so we have to pay attention to fIEld length. =*/= blen = PQgetlength(res,b_fnum); printf("tuple %d: got\n",i); printf(= ntohl(*((uint32_t *" i = (%d bytes) %d\n",PQgetlength(res,i_fnum),ival); printf("= t = (%d bytes) '%s'\n",t_fnum),tptr); printf(" b = (%d bytes) ",blen); for0) printf("\%03o",bptr[j]); printf("\n\n"); }} (j = int; j < blen; j++main(intcharargv){ constcharconninfo; PGconn conn; PGresult res; constchar1 argc,]; **int1 ]; *int*1*]; uint32_t binaryIntVal; /* * If the user supplIEs a parameter on the command line,PQerrorMessage(conn)); exit_nicely(conn); } *paramValues[/* * The point of this program is to illustrate use of PQexecParams() with * out-of-line parameters,as well as binary transmission of data. * * This first example transmits the parameters as text,but receives the * results in binary format. By using out-of-line parameters we can * avoID a lot of tedious mucking about with quoting and escaPing,even * though the data is text. Notice how we don't have to do anything * special with the quote mark in the parameter value. */ paramLengths[/* Here is our out-of-line parameter value */ paramFormats[ paramValues[0"joe's place"; res PQexecParams(conn, "SELECT * FROM test1 WHERE t = ",1] = /* one param */ NulL,=/* let the backend deduce param type */ paramValues,/* don't need param lengths since text ,*/ NulL,/* default to all text params */1/* ask for binary results */if PGRES_TUPLES_OK) { fprintf(stderr,"SELECT Failed: %s",PQerrorMessage(conn)); PQclear(res); exit_nicely(conn); } show_binary_results(res); PQclear(res); /*); * In this second example we transmit an integer parameter in binary * form,and again retrIEve the results in binary form. * * Although we tell PQexecParams we are letting the backend deduce * parameter type,we really force the decision by casting the parameter * symbol in the query text. This is a good safety measure when sending * binary parameters. *//* Convert integer value "2" to network byte order (PQresultStatus(res) !=*/ binaryIntVal 2); /* Set up parameter arrays for PQexecParams */ paramValues[ 0charbinaryIntVal; paramLengths[0= htonl((uint32_t) sizeof(binaryIntVal); paramFormats[01/* binary */] = ( res *) & PQexecParams(conn,"] = SELECT * FROM test1 WHERE i = ::int4",paramLengths,paramFormats,] = 1; /* ask for binary results */if= PGRES_TUPLES_OK) { fprintf(stderr,PQerrorMessage(conn)); PQclear(res); exit_nicely(conn); } show_binary_results(res); PQclear(res); /* close the connection to the database and cleanup */ PQfinish(conn); return); 0;} (PQresultStatus(res) !=总结
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