MFH:

Fix a bug with mysqlnd_fetch_field(_direct()). With mysqlnd the optimised
function was called, which however, doesn't respect that during store the
raw data is not unpacked, to be lazy. The data is unpacked to zvals later,
during every row fetch. However, this way max_length won't be calculated
correctly. So, if a mysqlnd_fetch_field(_direct) call comes we need to
unpack everything and then calculate max_length...and that is expensive,
defies our lazy unpacking optimisation.

1 files changed, 20 insertions, 0 deletions

diff --git a/ext/mysqlnd/mysqlnd_result.c b/ext/mysqlnd/mysqlnd_result.c
index e2c8c2c0af..f791fd0fb5 100644
--- a/ext/mysqlnd/mysqlnd_result.c
+++ b/ext/mysqlnd/mysqlnd_result.c
@@ -1736,6 +1736,16 @@ MYSQLND_METHOD(mysqlnd_res, fetch_field)(MYSQLND_RES * const result TSRMLS_DC)
 {
 	DBG_ENTER("mysqlnd_res::fetch_field");
 	if (result->meta) {
+		/*
+		  We optimize the result set, so we don't convert all the data from raw buffer format to
+		  zval arrays during store. In the case someone doesn't read all the lines this will
+		  save time. However, when a metadata call is done, we need to calculate max_length.
+		  We don't have control whether max_length will be used, unfortunately. Otherwise we
+		  could have been able to skip that step.
+		  Well, if the mysqli API switches from returning stdClass to class like mysqli_field_metadata,
+		  then we can have max_length as dynamic property, which will be calculated during runtime and
+		  not during mysqli_fetch_field() time.
+		*/
 		if (result->stored_data && (result->stored_data->initialized_rows < result->stored_data->row_count)) {
 			/* we have to initialize the rest to get the updated max length */
 			mysqlnd_res_initialize_result_set_rest(result TSRMLS_CC);
@@ -1754,6 +1764,16 @@ MYSQLND_METHOD(mysqlnd_res, fetch_field_direct)(MYSQLND_RES * const result,
 {
 	DBG_ENTER("mysqlnd_res::fetch_field_direct");
 	if (result->meta) {
+		/*
+		  We optimize the result set, so we don't convert all the data from raw buffer format to
+		  zval arrays during store. In the case someone doesn't read all the lines this will
+		  save time. However, when a metadata call is done, we need to calculate max_length.
+		  We don't have control whether max_length will be used, unfortunately. Otherwise we
+		  could have been able to skip that step.
+		  Well, if the mysqli API switches from returning stdClass to class like mysqli_field_metadata,
+		  then we can have max_length as dynamic property, which will be calculated during runtime and
+		  not during mysqli_fetch_field_direct() time.
+		*/
 		if (result->stored_data && (result->stored_data->initialized_rows < result->stored_data->row_count)) {
 			/* we have to initialized the rest to get the updated max length */
 			mysqlnd_res_initialize_result_set_rest(result TSRMLS_CC);