Cursor, seek by key

[Sergei Potapenko]

I created three keys, and seek resource parameters by keys 'uri' and 'id' (like RESTful service)
See code below (based on original example):

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <inttypes.h>
#include <assert.h>

#include "sophia.h"

int main(int argc, char *argv[])
{
    (void)argc;
    (void)argv;

    /* open or create environment and database */
    void *env = sp_env();
    sp_setstring(env, "sophia.path", "./sophia", 0);
    sp_setstring(env, "db", "restful", 0);
    sp_setstring(env, "db.restful.scheme", "uri", 0);
    sp_setstring(env, "db.restful.scheme", "id", 0);
    sp_setstring(env, "db.restful.scheme", "key", 0);
    sp_setstring(env, "db.restful.scheme", "value", 0);
    sp_setstring(env, "db.restful.scheme.uri",  "string,key(0)", 0);
    sp_setstring(env, "db.restful.scheme.id",   "u32,key(1)", 0);
    sp_setstring(env, "db.restful.scheme.key",  "string,key(2)", 0);
    sp_setstring(env, "db.restful.scheme.value", "string", 0);

    void *db = sp_getobject(env, "db.restful");

    int rc = sp_open(env);

    if (rc == -1)
        goto error;

    /* set */
    char* uri[] = { "user", "note", "comment"};
    char* key[] = { "name", "type", "class"};
    char  val[256] ={0};

    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            for (int k = 0; k < 3; k++)
            {
                void *o = sp_document(db);
                sp_setstring(o, "uri",  uri[i], 0);
                sp_setint(o, "id", j);
                sp_setstring(o, "key",  key[k], 0);

                sprintf(val, "%s/%"PRIu32"/%s", uri[i], j, key[k]);

                //fprintf(stderr, "%s\n", val);

                sp_setstring(o, "value",  val, 0);
                rc = sp_set(db, o);
                if (rc == -1)
                    goto error;
            }
        }
    }

    /* do forward iteration */
    void *cursor = sp_cursor(env);
    o = sp_document(db);
    //sp_setstring(o, "order", "=", 0);
    sp_setstring(o, "uri", "user", 0);
    sp_setint(o, "id", 1);
    while ((o = sp_get(cursor, o)))
    {
        int sz;
        char* ptr = sp_getstring(o, "value", &sz);
        int id = sp_getint(o, "id");

        if(ptr)
        {
            memcpy(val, ptr, sz);
            val[sz]=0;
            fprintf(stderr, "[%"PRIu32"] = %s\n", id, val);
        };
    }
    sp_destroy(cursor);

    /* finish work */
    sp_destroy(env);
    return 0;

error:
    ;
    int size;
    char *error = sp_getstring(env, "sophia.error", &size);
    printf("error: %s\n", error);
    free(error);
    sp_destroy(env);
    return 1;
}

I expect to see:

[1] = user/1/class
[1] = user/1/name
[1] = user/1/type

but realy I see:

[1] = user/1/class
[1] = user/1/name
[1] = user/1/type
[2] = user/2/class
[2] = user/2/name
[2] = user/2/type

How to seek items by key? By two keys?
Where can I read further about cursors? I have read here: http://charlesleifer.com/blog/announcing-sophy-fast-python-bindings-for-sophia-database/

Thank you, BR

[Dmitry Simonenko]

Hi,

When multi-part key is not completely specified (and order is default, which is '=') then cursor will be automatically set to >= and non-specified part will be assumed minimal value for the field-type. In other words, sophia will position its cursor for key { a, b, MIN }.

If you need to return only first record which matches non-complete key, you may try to stop iteration after first sp_get(cursor) invocation or you can try not to use cursors and ask database directly, like this:

void *key = sp_document(db);
sp_setstring(key, "uri", ...);
sp_setstring(key, "id", ...);
sp_setstring(key, "order", ">=");
void *result = sp_get(key);
if (result) {
   /* will return first record which matches uri and id */
   sp_destroy(result);
}

Cursor usage documentation is here: http://sophia.systems/v2.2/crud/cursors.html but yet it
might be not complete and lack of such examples, sorry.