On 03/04/2017 23:08, Clemens Ladisch wrote:
I think you can work around these problems by moving the blob value into
a separate table.
I thought so too. However, even updates to other tables invalidate the
blob handle. Please see the example below.
Variable breakMe breaks the second sqlite3_blob_write call, even though
the added update statement is for the other table.
Yuri
#include <stdio.h>
#include <stdlib.h>
#include "sqlite3.h"
int breakMe = 1;
char *exec_errmsg;
void execSql(sqlite3 *db, const char *sql) {
int rc;
if (SQLITE_OK != (rc = sqlite3_exec(db, sql, NULL, NULL,
&exec_errmsg))) {
fprintf(stderr, "Error while executing sql=%s, error=%d\n", sql, rc);
exit(1);
}
}
int main(int argc, char **argv) {
sqlite3 *db = NULL;
int rc;
rc = sqlite3_open(argv[1], &db);
if (SQLITE_OK != rc) {
fprintf(stderr, "Can't open database %s (%i): %s\n", argv[1], rc,
sqlite3_errmsg(db));
exit(1);
}
execSql(db, "CREATE TABLE fragmented_data ( friend_id INTEGER NOT
NULL, frags_id INTEGER NOT NULL, message BLOB, PRIMARY KEY (
friend_id, frags_id));");
execSql(db, "CREATE TABLE fragmented_meta ( friend_id INTEGER NOT
NULL, frags_id INTEGER NOT NULL, timestamp_first INTEGER NOT
NULL, timestamp_last INTEGER NOT NULL, frags_done INTEGER NOT
NULL, frags_num INTEGER NOT NULL, message BLOB, PRIMARY
KEY ( friend_id, frags_id));");
execSql(db, "INSERT INTO fragmented_data (friend_id, frags_id,
message) SELECT 0, 1488703606591, zeroblob(2070) WHERE NOT EXISTS
(SELECT 1 FROM fragmented_meta WHERE friend_id=0 AND
frags_id=1488703606591);");
execSql(db, "INSERT INTO fragmented_meta (friend_id, frags_id,
timestamp_first, timestamp_last, frags_done, frags_num) SELECT 0,
1488703606591, 1488703647556, 1488703647556, 0, 2 WHERE NOT EXISTS
(SELECT 1 FROM fragmented_meta WHERE friend_id=0 AND
frags_id=1488703606591);");
sqlite3_blob *blob1;
rc = sqlite3_blob_open(db, "main", "fragmented_data", "message", 1,
1, &blob1);
if (SQLITE_OK != rc) {
fprintf(stderr, "Couldn't get blob handle (%i): %s\n", rc,
sqlite3_errmsg(db));
exit(1);
}
if (SQLITE_OK != (rc = sqlite3_blob_write(blob1, "1", 1, 0x10))) {
fprintf(stderr, "Error writing to blob handle #1. rc=%d\n", rc);
exit(1);
}
if (breakMe)
execSql(db, "UPDATE fragmented_meta SET
timestamp_last=max(timestamp_last,1488703647556), frags_done =
frags_done+1 WHERE friend_id=0 AND frags_id=1488703606591;");
if (SQLITE_OK != (rc = sqlite3_blob_write(blob1, "2", 1, 0x250))) {
fprintf(stderr, "Error writing to blob handle #2. rc=%d\n", rc);
exit(1);
}
sqlite3_blob_close(blob1);
printf("Successfully wrote to blob\n");
sqlite3_close(db);
return 0;
}
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