Merge pull request mysql#18 from planetscale/piki/unmetered-vt-for-8.0.28

Cherry-pick mysql#17 for 8.0.28 (unmetered reads prefixes)

Author: piki

storage/innobase/dict/mem.cc

@@ -35,6 +35,7 @@ this program; if not, write to the Free Software Foundation, Inc.,
 other files in library. The code in this file is used to make a library for
 external tools. */
 
+#include <algorithm>
 #include <new>
 
 #include "dict0dict.h"
@@ -147,35 +148,36 @@ void dict_mem_table_free(dict_table_t *table) /*!< in: table */
 }
 
 /** System databases */
-static std::string innobase_system_databases[] = {
-    "mysql/", "information_schema/", "performance_schema/", ""};
+static std::vector<std::string> innobase_system_databases({
+    "mysql/", "information_schema/", "performance_schema/"
+});
 
 /** Determines if a table is a system table
 @param[in]  name  table_name
 @return true if table is system table */
-static bool dict_mem_table_is_system(const std::string name) {
+static bool dict_mem_table_is_system(const std::string &name) {
   /* Table has the following format: database/table and some system table are
   of the form SYS_* */
-  if (name.find('/') != std::string::npos) {
-    size_t table_len = name.length();
-
-    std::string system_db = std::string(innobase_system_databases[0]);
-    int i = 0;
+  if (name.find('/') == std::string::npos)
+    return true;
 
-    while (system_db.compare("") != 0) {
-      size_t len = system_db.length();
+  for (auto p : innobase_system_databases) {
+    if (name.length() > p.length() && name.compare(0, p.length(), p) == 0)
+      return true;
+  }
 
-      if (table_len > len && name.compare(0, len, system_db) == 0) {
-        return true;
-      }
+  return false;
+}
 
-      system_db = std::string(innobase_system_databases[++i]);
-    }
+void dict_add_system_prefix(const char *pfx) {
+  if (!pfx || !pfx[0])
+    return;
 
-    return false;
-  } else {
-    return true;
-  }
+  std::string pfx_s = pfx;
+  if (pfx_s[pfx_s.size()-1] != '/')
+    pfx_s += '/';
+  if (std::find(innobase_system_databases.begin(), innobase_system_databases.end(), pfx_s) == innobase_system_databases.end())
+    innobase_system_databases.push_back(pfx_s);
 }
 
 /** Creates a table memory object.

storage/innobase/dict/mem.h

@@ -91,4 +91,9 @@ const char *dict_add_col_name(const char *col_names, /*!< in: existing column
                               ulint cols, /*!< in: number of existing columns */
                               const char *name,  /*!< in: new column name */
                               mem_heap_t *heap); /*!< in: heap */
+
+/** Add the prefix 'pfx' to the list of database names that count as
+ * system tables, rather than user tables, for the purposes of rows
+ * {read,inserted,updated,deleted} counters. */
+void dict_add_system_prefix(const char *pfx);
 #endif

storage/innobase/handler/ha_innodb.cc

@@ -310,6 +310,10 @@ static ulong innodb_flush_method;
 stopword table to be used */
 static char *innobase_server_stopword_table = nullptr;
 
+/* A comma-separated list of prefixes that designate system (not user) tables
+for metrics accounting.  See also dict_mem_table_is_system. */
+static char *extra_system_table_prefixes = nullptr;
+
 /* Below we have boolean-valued start-up parameters, and their default
 values */
 
@@ -5446,6 +5450,15 @@ static int innobase_init_files(dict_init_mode_t dict_init_mode,
   /* Turn on monitor counters that are default on */
   srv_mon_default_on();
 
+  if (extra_system_table_prefixes) {
+    char *copy = strdup(extra_system_table_prefixes);
+    char *saveptr, *tok;
+    for (tok=my_strtok_r(copy, ",", &saveptr); tok; tok=my_strtok_r(NULL, ",", &saveptr)) {
+      dict_add_system_prefix(tok);
+    }
+    free(copy);
+  }
+
   /* Unit Tests */
 #ifdef UNIV_ENABLE_UNIT_TEST_GET_PARENT_DIR
   unit_test_os_file_get_parent_dir();
@@ -21797,6 +21810,12 @@ static MYSQL_SYSVAR_STR(ft_server_stopword_table,
                         "The user supplied stopword table name.",
                         innodb_stopword_table_validate, nullptr, nullptr);
 
+static MYSQL_SYSVAR_STR(extra_system_table_prefixes,
+                        extra_system_table_prefixes,
+                        PLUGIN_VAR_READONLY | PLUGIN_VAR_NOSYSVAR | PLUGIN_VAR_RQCMDARG,
+                        "Additional prefixes that designate system (not user) tables for metrics accounting.",
+                        nullptr, nullptr, nullptr);
+
 extern uint srv_flush_log_at_timeout;
 static MYSQL_SYSVAR_UINT(flush_log_at_timeout, srv_flush_log_at_timeout,
                          PLUGIN_VAR_OPCMDARG,
@@ -23006,6 +23025,7 @@ static SYS_VAR *innobase_system_variables[] = {
     MYSQL_SYSVAR(ft_aux_table),
     MYSQL_SYSVAR(ft_enable_diag_print),
     MYSQL_SYSVAR(ft_server_stopword_table),
+    MYSQL_SYSVAR(extra_system_table_prefixes),
     MYSQL_SYSVAR(ft_user_stopword_table),
     MYSQL_SYSVAR(disable_sort_file_cache),
     MYSQL_SYSVAR(stats_on_metadata),