database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-30 16:24:05 +03:00
Code Activity

MDEV-19237 Skip sending metadata when possible for binary protocol.

Browse Source 
Do not resend metadata, if metadata does not change between prepare and
execute of prepared statement, or between executes.

Currently, metadata of *every* prepared statement will be checksummed,
and change is detected once checksum changes.

This is not from ideal, performance-wise. The code for
better/faster detection of unchanged metadata, is already in place, but
currently disabled due to PS bugs, such as MDEV-23913.
This commit is contained in:
Vladislav Vaintroub
2020-11-23 19:24:31 +01:00
parent a62a675fd2
commit 295f3e4cfb
8 changed files with 450 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
sql/sql_class.h
View File

@ -929,6 +929,12 @@ typedef struct system_status_var
ulong access_denied_errors;
ulong lost_connections;
ulong max_statement_time_exceeded;
/*
Number of times where column info was not
sent with prepared statement metadata.
*/
ulong skip_metadata_count;
/*
Number of statements sent from the client
*/
@ -948,6 +954,7 @@ typedef struct system_status_var
ulonglong table_open_cache_hits;
ulonglong table_open_cache_misses;
ulonglong table_open_cache_overflows;
ulonglong send_metadata_skips;
double last_query_cost;
double cpu_time, busy_time;
uint32 threads_running;
@ -1193,6 +1200,38 @@ public:
class Server_side_cursor;
/*
Struct to catch changes in column metadata that is sent to client.
in the "result set metadata". Used to support
MARIADB_CLIENT_CACHE_METADATA.
*/
struct send_column_info_state
{
/* Last client charset (affects metadata) */
CHARSET_INFO *last_charset= nullptr;
/* Checksum, only used to check changes if 'immutable' is false*/
uint32 checksum= 0;
/*
Column info can only be changed by PreparedStatement::reprepare()
There is a class of "weird" prepared statements like SELECT ? or SELECT @a
that are not immutable, and depend on input parameters or user variables
*/
bool immutable= false;
bool initialized= false;
/* Used by PreparedStatement::reprepare()*/
void reset()
{
initialized= false;
checksum= 0;
}
};
/**
@class Statement
@brief State of a single command executed against this connection.
@ -1282,6 +1321,8 @@ public:
LEX_CSTRING db;
send_column_info_state column_info_state;
/* This is set to 1 of last call to send_result_to_client() was ok */
my_bool query_cache_is_applicable;
@ -2385,6 +2426,8 @@ public:
/* Last created prepared statement */
Statement *last_stmt;
Statement *cur_stmt= 0;
inline void set_last_stmt(Statement *stmt)
{ last_stmt= (is_error() ? NULL : stmt); }
inline void clear_last_stmt() { last_stmt= NULL; }