No comment? Do I need to recast the problem or something?
Thanks,
scott
On Fri, Apr 26, 2013 at 9:54 PM, Scott Hess <sh...@google.com> wrote:
> Someone over here was trying to use a shared-cache in-memory database with
> two connections, one a read-write connection for purposes of populating
> things, the other a read-only connection for purposes of letting a (trusted)
> user make queries. They were surprised to find out that they could run
> write queries against the read-only handle (the insert query in my example).
> Also, if you flip the order of the opens so that the read-only open happens
> first, then the create statement fails with SQLITE_READONLY.
>
> [Aside: I suggested that it might be more appropriate to use an authorizer,
> rather than try to open an in-memory database read-only.]
>
> A couple minutes in the code makes me think that the sense of "cache=shared"
> is implemented at the btree.c layer, so it is somewhat unlikely that this is
> reasonable to actually support. That said, it is unexpected. It seems like
> the library should throw something like SQLITE_MISUSE when you request a
> shared-cache open incompatible with previous opens. WDYT?
>
> The same basic problem also appears to happen for on-disk databases, which
> makes me wonder if we're just doing something wrong.
>
> Thanks,
> scott
>
> ---
> /* gcc -g -o sqlmem sqlmem.c sqlite3.c */
>
> #include "sqlite3.h"
> #include <stdio.h>
>
> int main(int argc, char** argv) {
> sqlite3* rw;
> sqlite3* ro;
> int rc;
> char* err;
>
> rc = sqlite3_open_v2("file::memory:?cache=shared", &rw,
> SQLITE_OPEN_READWRITE | SQLITE_OPEN_URI, NULL);
> if (rc!=SQLITE_OK) {
> fprintf(stderr, "rw rc==%d\n", rc);
> return 1;
> }
>
> rc = sqlite3_open_v2("file::memory:?cache=shared", &ro,
> SQLITE_OPEN_READONLY | SQLITE_OPEN_URI, NULL);
> if (rc!=SQLITE_OK) {
> fprintf(stderr, "ro rc==%d\n", rc);
> return 1;
> }
>
> rc = sqlite3_exec(rw, "CREATE TABLE t (a TEXT)", NULL, NULL, &err);
> if (rc!=SQLITE_OK) {
> fprintf(stderr, "rw create error: %d/%s\n", rc, err);
> return 1;
> }
>
> rc = sqlite3_exec(ro, "SELECT 1", NULL, NULL, &err);
> if (rc!=SQLITE_OK) {
> fprintf(stderr, "ro select error: %d/%s\n", rc, err);
> return 1;
> }
>
> rc = sqlite3_exec(ro, "INSERT INTO t (a) VALUES ('a')", NULL, NULL, &err);
> if (rc!=SQLITE_OK) {
> fprintf(stderr, "ro insert error: %d/%s\n", rc, err);
> return 1;
> } else {
> fprintf(stderr, "ro insert succeeeded?\n");
> return 1;
> }
> }
>
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