MySQLnd: Support cursors in store/get result

This fixes two related issues:

1. When a PS with cursor is used in store_result/get_result,
   perform a COM_FETCH with maximum number of rows rather than
   silently switching to an unbuffered result set (in the case of
   store_result) or erroring (in the case of get_result).
   In the future, we might want to make get_result unbuffered for
   PS with cursors, as using cursors with buffered result sets
   doesn't really make sense. Unlike store_result, get_result
   isn't very explicit about what kind of result set is desired.
2. If the client did not request a cursor, but the server reports
   that a cursor exists, ignore this and treat the PS as if it
   has no cursor (i.e. to not use COM_FETCH). It appears to be a
   server side bug that a cursor used inside an SP will be reported
   to the client, even though the client cannot use the cursor.

Fixes bug #64638, bug #72862, bug #77935.

Closes GH-6518.

1 files changed, 72 insertions, 59 deletions

diff --git a/ext/mysqlnd/mysqlnd_ps.c b/ext/mysqlnd/mysqlnd_ps.c
index eda9c312d5..12aace6ec2 100644
--- a/ext/mysqlnd/mysqlnd_ps.c
+++ b/ext/mysqlnd/mysqlnd_ps.c
@@ -40,6 +40,36 @@ enum_func_status mysqlnd_stmt_execute_batch_generate_request(MYSQLND_STMT * cons
 static void mysqlnd_stmt_separate_result_bind(MYSQLND_STMT * const stmt);
 static void mysqlnd_stmt_separate_one_result_bind(MYSQLND_STMT * const stmt, const unsigned int param_no);
 
+static enum_func_status mysqlnd_stmt_send_cursor_fetch_command(
+		const MYSQLND_STMT_DATA *stmt, unsigned max_rows)
+{
+	MYSQLND_CONN_DATA *conn = stmt->conn;
+	zend_uchar buf[MYSQLND_STMT_ID_LENGTH /* statement id */ + 4 /* number of rows to fetch */];
+	const MYSQLND_CSTRING payload = {(const char*) buf, sizeof(buf)};
+
+	int4store(buf, stmt->stmt_id);
+	int4store(buf + MYSQLND_STMT_ID_LENGTH, max_rows);
+
+	if (conn->command->stmt_fetch(conn, payload) == FAIL) {
+		COPY_CLIENT_ERROR(stmt->error_info, *conn->error_info);
+		return FAIL;
+	}
+	return PASS;
+}
+
+static zend_bool mysqlnd_stmt_check_state(const MYSQLND_STMT_DATA *stmt)
+{
+	const MYSQLND_CONN_DATA *conn = stmt->conn;
+	if (stmt->state != MYSQLND_STMT_WAITING_USE_OR_STORE) {
+		return 0;
+	}
+	if (stmt->cursor_exists) {
+		return GET_CONNECTION_STATE(&conn->state) == CONN_READY;
+	} else {
+		return GET_CONNECTION_STATE(&conn->state) == CONN_FETCHING_DATA;
+	}
+}
+
 /* {{{ mysqlnd_stmt::store_result */
 static MYSQLND_RES *
 MYSQLND_METHOD(mysqlnd_stmt, store_result)(MYSQLND_STMT * const s)
@@ -60,14 +90,8 @@ MYSQLND_METHOD(mysqlnd_stmt, store_result)(MYSQLND_STMT * const s)
 		DBG_RETURN(NULL);
 	}
 
-	if (stmt->cursor_exists) {
-		/* Silently convert buffered to unbuffered, for now */
-		DBG_RETURN(s->m->use_result(s));
-	}
-
 	/* Nothing to store for UPSERT/LOAD DATA*/
-	if (GET_CONNECTION_STATE(&conn->state) != CONN_FETCHING_DATA || stmt->state != MYSQLND_STMT_WAITING_USE_OR_STORE)
-	{
+	if (!mysqlnd_stmt_check_state(stmt)) {
 		SET_CLIENT_ERROR(conn->error_info, CR_COMMANDS_OUT_OF_SYNC, UNKNOWN_SQLSTATE, mysqlnd_out_of_sync);
 		DBG_RETURN(NULL);
 	}
@@ -78,6 +102,12 @@ MYSQLND_METHOD(mysqlnd_stmt, store_result)(MYSQLND_STMT * const s)
 	SET_EMPTY_ERROR(conn->error_info);
 	MYSQLND_INC_CONN_STATISTIC(conn->stats, STAT_PS_BUFFERED_SETS);
 
+	if (stmt->cursor_exists) {
+		if (mysqlnd_stmt_send_cursor_fetch_command(stmt, -1) == FAIL) {
+			DBG_RETURN(NULL);
+		}
+	}
+
 	result = stmt->result;
 	result->type			= MYSQLND_RES_PS_BUF;
 /*	result->m.row_decoder = php_mysqlnd_rowp_read_binary_protocol; */
@@ -152,19 +182,8 @@ MYSQLND_METHOD(mysqlnd_stmt, get_result)(MYSQLND_STMT * const s)
 		DBG_RETURN(NULL);
 	}
 
-	if (stmt->cursor_exists) {
-		/* Prepared statement cursors are not supported as of yet */
-		char * msg;
-		mnd_sprintf(&msg, 0, "%s() cannot be used with cursors", get_active_function_name());
-		SET_CLIENT_ERROR(stmt->error_info, CR_NOT_IMPLEMENTED, UNKNOWN_SQLSTATE, msg);
-		if (msg) {
-			mnd_sprintf_free(msg);
-		}
-		DBG_RETURN(NULL);
-	}
-
 	/* Nothing to store for UPSERT/LOAD DATA*/
-	if (GET_CONNECTION_STATE(&conn->state) != CONN_FETCHING_DATA || stmt->state != MYSQLND_STMT_WAITING_USE_OR_STORE) {
+	if (!mysqlnd_stmt_check_state(stmt)) {
 		SET_CLIENT_ERROR(stmt->error_info, CR_COMMANDS_OUT_OF_SYNC, UNKNOWN_SQLSTATE, mysqlnd_out_of_sync);
 		DBG_RETURN(NULL);
 	}
@@ -173,6 +192,12 @@ MYSQLND_METHOD(mysqlnd_stmt, get_result)(MYSQLND_STMT * const s)
 	SET_EMPTY_ERROR(conn->error_info);
 	MYSQLND_INC_CONN_STATISTIC(conn->stats, STAT_BUFFERED_SETS);
 
+	if (stmt->cursor_exists) {
+		if (mysqlnd_stmt_send_cursor_fetch_command(stmt, -1) == FAIL) {
+			DBG_RETURN(NULL);
+		}
+	}
+
 	do {
 		result = conn->m->result_init(stmt->result->field_count);
 		if (!result) {
@@ -561,28 +586,30 @@ mysqlnd_stmt_execute_parse_response(MYSQLND_STMT * const s, enum_mysqlnd_parse_e
 			DBG_INF_FMT("server_status=%u cursor=%u", UPSERT_STATUS_GET_SERVER_STATUS(stmt->upsert_status),
 						UPSERT_STATUS_GET_SERVER_STATUS(stmt->upsert_status) & SERVER_STATUS_CURSOR_EXISTS);
 
-			if (UPSERT_STATUS_GET_SERVER_STATUS(stmt->upsert_status) & SERVER_STATUS_CURSOR_EXISTS) {
-				DBG_INF("cursor exists");
-				stmt->cursor_exists = TRUE;
-				SET_CONNECTION_STATE(&conn->state, CONN_READY);
-				/* Only cursor read */
-				stmt->default_rset_handler = s->m->use_result;
-				DBG_INF("use_result");
-			} else if (stmt->flags & CURSOR_TYPE_READ_ONLY) {
-				DBG_INF("asked for cursor but got none");
-				/*
-				  We have asked for CURSOR but got no cursor, because the condition
-				  above is not fulfilled. Then...
-
-				  This is a single-row result set, a result set with no rows, EXPLAIN,
-				  SHOW VARIABLES, or some other command which either a) bypasses the
-				  cursors framework in the server and writes rows directly to the
-				  network or b) is more efficient if all (few) result set rows are
-				  precached on client and server's resources are freed.
-				*/
-				/* preferred is buffered read */
-				stmt->default_rset_handler = s->m->store_result;
-				DBG_INF("store_result");
+			if (stmt->flags & CURSOR_TYPE_READ_ONLY) {
+				if (UPSERT_STATUS_GET_SERVER_STATUS(stmt->upsert_status) & SERVER_STATUS_CURSOR_EXISTS) {
+					DBG_INF("cursor exists");
+					stmt->cursor_exists = TRUE;
+					SET_CONNECTION_STATE(&conn->state, CONN_READY);
+					/* Only cursor read */
+					stmt->default_rset_handler = s->m->use_result;
+					DBG_INF("use_result");
+				} else {
+					DBG_INF("asked for cursor but got none");
+					/*
+					  We have asked for CURSOR but got no cursor, because the condition
+					  above is not fulfilled. Then...
+
+					  This is a single-row result set, a result set with no rows, EXPLAIN,
+					  SHOW VARIABLES, or some other command which either a) bypasses the
+					  cursors framework in the server and writes rows directly to the
+					  network or b) is more efficient if all (few) result set rows are
+					  precached on client and server's resources are freed.
+					*/
+					/* preferred is buffered read */
+					stmt->default_rset_handler = s->m->store_result;
+					DBG_INF("store_result");
+				}
 			} else {
 				DBG_INF("no cursor");
 				/* preferred is unbuffered read */
@@ -940,11 +967,7 @@ MYSQLND_METHOD(mysqlnd_stmt, use_result)(MYSQLND_STMT * s)
 	}
 	DBG_INF_FMT("stmt=%lu", stmt->stmt_id);
 
-	if (!stmt->field_count ||
-		(!stmt->cursor_exists && GET_CONNECTION_STATE(&conn->state) != CONN_FETCHING_DATA) ||
-		(stmt->cursor_exists && GET_CONNECTION_STATE(&conn->state) != CONN_READY) ||
-		(stmt->state != MYSQLND_STMT_WAITING_USE_OR_STORE))
-	{
+	if (!stmt->field_count || !mysqlnd_stmt_check_state(stmt)) {
 		SET_CLIENT_ERROR(conn->error_info, CR_COMMANDS_OUT_OF_SYNC, UNKNOWN_SQLSTATE, mysqlnd_out_of_sync);
 		DBG_ERR("command out of sync");
 		DBG_RETURN(NULL);
@@ -974,7 +997,6 @@ mysqlnd_fetch_stmt_row_cursor(MYSQLND_RES * result, void * param, const unsigned
 	MYSQLND_STMT * s = (MYSQLND_STMT *) param;
 	MYSQLND_STMT_DATA * stmt = s? s->data : NULL;
 	MYSQLND_CONN_DATA * conn = stmt? stmt->conn : NULL;
-	zend_uchar buf[MYSQLND_STMT_ID_LENGTH /* statement id */ + 4 /* number of rows to fetch */];
 	MYSQLND_PACKET_ROW * row_packet;
 
 	DBG_ENTER("mysqlnd_fetch_stmt_row_cursor");
@@ -998,18 +1020,9 @@ mysqlnd_fetch_stmt_row_cursor(MYSQLND_RES * result, void * param, const unsigned
 	SET_EMPTY_ERROR(stmt->error_info);
 	SET_EMPTY_ERROR(conn->error_info);
 
-	int4store(buf, stmt->stmt_id);
-	int4store(buf + MYSQLND_STMT_ID_LENGTH, 1); /* for now fetch only one row */
-
-	{
-		const MYSQLND_CSTRING payload = {(const char*) buf, sizeof(buf)};
-
-		ret = conn->command->stmt_fetch(conn, payload);
-		if (ret == FAIL) {
-			COPY_CLIENT_ERROR(stmt->error_info, *conn->error_info);
-			DBG_RETURN(FAIL);
-		}
-
+	/* for now fetch only one row */
+	if (mysqlnd_stmt_send_cursor_fetch_command(stmt, 1) == FAIL) {
+		DBG_RETURN(FAIL);
 	}
 
 	row_packet->skip_extraction = stmt->result_bind? FALSE:TRUE;