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Prevent command out of sync errors with Prepared Statements #958

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merged 1 commit into from
Apr 7, 2018
Merged

Prevent command out of sync errors with Prepared Statements #958

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43 changes: 32 additions & 11 deletions ext/mysql2/statement.c
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Original file line number Diff line number Diff line change
Expand Up @@ -403,6 +403,38 @@ static VALUE rb_mysql_stmt_execute(int argc, VALUE *argv, VALUE self) {
}
}

// Duplicate the options hash, merge! extra opts, put the copy into the Result object
current = rb_hash_dup(rb_iv_get(stmt_wrapper->client, "@query_options"));
(void)RB_GC_GUARD(current);
Check_Type(current, T_HASH);

// Merge in hash opts/keyword arguments
if (!NIL_P(opts)) {
rb_funcall(current, intern_merge_bang, 1, opts);
}

is_streaming = (Qtrue == rb_hash_aref(current, sym_stream));

// From stmt_execute to mysql_stmt_result_metadata to stmt_store_result, no
// Ruby API calls are allowed so that GC is not invoked. If the connection is
// in results-streaming-mode for Statement A, and in the middle Statement B
// gets garbage collected, a message will be sent to the server notifying it
// to release Statement B, resulting in the following error:
// Commands out of sync; you can't run this command now
//
// In streaming mode, statement execute must return a cursor because we
// cannot prevent other Statement objects from being garbage collected
// between fetches of each row of the result set. The following error
// occurs if cursor mode is not set:
// Row retrieval was canceled by mysql_stmt_close

if (is_streaming) {
unsigned long type = CURSOR_TYPE_READ_ONLY;
if (mysql_stmt_attr_set(stmt, STMT_ATTR_CURSOR_TYPE, &type)) {
rb_raise(cMysql2Error, "Unable to stream prepared statement, could not set CURSOR_TYPE_READ_ONLY");
}
}

if ((VALUE)rb_thread_call_without_gvl(nogvl_stmt_execute, stmt, RUBY_UBF_IO, 0) == Qfalse) {
FREE_BINDS;
rb_raise_mysql2_stmt_error(stmt_wrapper);
Expand All @@ -421,17 +453,6 @@ static VALUE rb_mysql_stmt_execute(int argc, VALUE *argv, VALUE self) {
return Qnil;
}

// Duplicate the options hash, merge! extra opts, put the copy into the Result object
current = rb_hash_dup(rb_iv_get(stmt_wrapper->client, "@query_options"));
(void)RB_GC_GUARD(current);
Check_Type(current, T_HASH);

// Merge in hash opts/keyword arguments
if (!NIL_P(opts)) {
rb_funcall(current, intern_merge_bang, 1, opts);
}

is_streaming = (Qtrue == rb_hash_aref(current, sym_stream));
if (!is_streaming) {
// recieve the whole result set from the server
if (mysql_stmt_store_result(stmt)) {
Expand Down