Add C/PostgreSQL version

Makefile

@@ -0,0 +1,6 @@
+CFLAGS=-I/usr/include/postgresql -O3
+
+all: dcb_c_psql
+
+dcb_c_psql: dcb_c_psql.o
+	$(CC) -o $@ $^ -lpq

dcb_c_psql.c

@@ -0,0 +1,88 @@
+/*
+ * This program is based on
+ * src/test/examples/testlibpq.c (example 33.1)
+ * from section 33.21 of the PostgreSQL documentation
+ * (https://www.postgresql.org/docs/13/libpq-example.html)
+ *
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include "libpq-fe.h"
+
+static void
+exit_nicely(PGconn *conn)
+{
+    PQfinish(conn);
+    exit(1);
+}
+
+int
+main(int argc, char **argv)
+{
+    const char *conninfo;
+    PGconn     *conn;
+    PGresult   *res;
+    int         nFields;
+    int         i,
+                j;
+    struct timespec ts0, ts1, ts2, ts3, ts4;
+
+    /*
+     * 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 = "";
+
+    clock_gettime(CLOCK_MONOTONIC, &ts0);
+
+    /* 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);
+    }
+    clock_gettime(CLOCK_MONOTONIC, &ts1);
+
+    res = PQexec(conn, "select current_timestamp");
+    if (PQresultStatus(res) != PGRES_TUPLES_OK)
+    {
+        fprintf(stderr, "Select command 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);
+    clock_gettime(CLOCK_MONOTONIC, &ts2);
+
+    /* close the connection to the database and cleanup */
+    PQfinish(conn);
+    clock_gettime(CLOCK_MONOTONIC, &ts3);
+    printf("%f connect\n", (ts1.tv_sec - ts0.tv_sec) + (ts1.tv_nsec - ts0.tv_nsec) * 1E-9);
+    printf("%f session\n", (ts3.tv_sec - ts0.tv_sec) + (ts3.tv_nsec - ts0.tv_nsec) * 1E-9);
+
+    return 0;
+}
+