Perhaps because you are committing the transaction? > -----Original Message----- > From: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] > On Behalf Of Yuri > Sent: Sunday, 5 March, 2017 02:27 > To: SQLite mailing list > Subject: Re: [sqlite] Can sqlite3_blob_write be done through SQL? > > 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; > } > > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
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