iOS sqlite blob write fails with 'unknown error'

Question

I have an SQLite-based app that works fine on Windows, Android and Java. I am trying to port it to iOS: the device is running iOS 9.3.1.

Everything else works apart from the blob write, which fails on the sqlite_step call with an "unknown error". The code is based on this SE post.

This is a stripped-down version of the low-level SQLite interface: the query comes from the next level up.

NSLog (@"Preparing query {%s}", query);
rc = sqlite3_prepare_v2 (hdb, query, -1, &stmt, &tail);
if (rc == SQLITE_OK) {
   NSLog (@"Binding blob: size= %d", (int)[blob length]);
   rc = sqlite3_bind_blob (stmt, 1, [blob bytes], (int) [blob length], SQLITE_STATIC);
   if (rc == SQLITE_OK) {
      rc = sqlite3_step (stmt);
      if (rc != SQLITE_OK)
        [self sql_error: @"sqlDo" line: __LINE__];
   }
   if (sqlite3_finalize (stmt) != SQLITE_OK)
     [self sql_error: @"sqlEndQuery" line: __LINE__];

 }

This is the NSLog output:

Preparing query {INSERT OR REPLACE INTO xxx VALUES (18356, '', ?)}
Binding blob: size= 5388
SQL error at line 157 in sqlDo: query:{INSERT OR REPLACE INTO xxx VALUES (18356, '', ?)} message:{unknown error}

@rmaddy: That is the actual query, apart from replacing the table name by xxx for reasons of confidentiality. — JavaLatte
– JavaLatte, Commented Apr 7, 2016 at 16:45
Do you list three column names after the table name? ... INTO FOO (Col1, Col2, Col3) VALUES .... — rmaddy
– rmaddy, Commented Apr 7, 2016 at 16:46
I am writing all of the columns, so the column names are optional. here is the structure of the table: CREATE TABLE [xxx] ( [field1] INTEGER PRIMARY KEY, [field2] TEXT, [field3] BLOB); — JavaLatte
– JavaLatte, Commented Apr 7, 2016 at 16:55
@Rob, it will still break, but in a subtler way. I'd rather have it crash and burn while I'm testing than risk shipping a production system that's writing records with fields missing. — JavaLatte
– JavaLatte, Commented Apr 7, 2016 at 17:03

Rob · Accepted Answer · 2016-04-07 16:55:33Z

1

After performing a sqlite3_step of an INSERT statement, the result is SQLITE_DONE, not SQLITE_OK.

So, you want:

rc = sqlite3_step(stmt);
if (rc != SQLITE_DONE)
    [self sql_error: @"sqlDo" line: __LINE__];

answered Apr 7, 2016 at 16:55

Rob

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