MDEV-32157 MDEV-28856 Spider: Tests, documentation, small fixes and cleanups

Removed some redundant hint related string literals from
spd_db_conn.cc

Clean up SPIDER_PARAM_*_[CHAR]LEN[S]

Adding tests covering monitoring_kind=2. What it does is that it reads
from mysql.spider_link_mon_servers with matching db_name, table_name,
link_id, and does not do anything about that...

How monitoring_* can be useful: in the deprecated spider high
availability feature, when one remote fails, spider will try another
remote, which apparently makes use of these table parameters.

A test covering the query_cache_sync table param. Some further tests
on some spider table params.

Wrapper should be case insensitive.

Code documentation on spider priority binary tree.

Add an assertion that static_key_cardinality is always -1. All tests
pass still

storage/spider/ha_spider.cc

@@ -6934,6 +6934,10 @@ ha_rows ha_spider::records_in_range(
   dbton_id = share->sql_dbton_ids[search_link_idx];
   dbton_hdl = dbton_handler[dbton_id];
   crd_mode = dbton_hdl->crd_mode_exchange(crd_mode);
+  /* This assertion simply demonstrates that the
+  static_key_cardinality field is unused. It will be deprecated
+  (MDEV-28861) and removed (MDEV-31146). */
+  DBUG_ASSERT(share->static_key_cardinality[inx] == -1);
   if (crd_mode == 1 || crd_mode == 2)
   {
     DBUG_PRINT("info", ("spider static_key_cardinality[%u]=%lld", inx,

storage/spider/mysql-test/spider/bugfix/r/mdev_28856.result

+#
+# MDEV-28856 Spider: Implement more engine-defined options
+#
+for master_1
+for child2
+for child3
+CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+# testing monitoring_*
+INSERT INTO mysql.spider_link_mon_servers
+(db_name, table_name, link_id, sid, server) VALUES
+('test', 't1', '0', 1, 'srv');
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", monitoring_kind "2"';
+/* 1 */ insert into t1 values (42);
+ERROR HY000: Table 'test.t2' get a problem
+/* 2 */ insert into t1 values (42);
+ERROR HY000: All links of 'test.t1' are failed
+create table t2 (c int);
+/* 3 */ insert into t1 values (42);
+ERROR HY000: All links of 'test.t1' are failed
+drop table t1, t2;
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", monitoring_bg_kind "2",
+         monitoring_bg_interval "500000"';
+/* 4 */ insert into t1 values (42);
+ERROR 42S02: Table 'test.t2' doesn't exist
+drop table t1;
+# testing query_cache_sync
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", query_cache_sync "3"';
+create table t2 (c int);
+/* 5 */ insert into t1 values (42);
+select sql_cache * from t1;
+c
+42
+select sql_no_cache * from t1;
+c
+42
+drop table t1, t2;
+# testing tgt_pk_names
+create table t2 (c int);
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+/* 6 */ insert ignore into t1 values (42), (42);
+select * from t1;
+c
+42
+42
+drop table t1, t2;
+create table t2 (c int, primary key (c));
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+/* 7 */ insert ignore into t1 values (42), (42);
+Warnings:
+Warning	1022	Can't write; duplicate key in table 't1'
+select * from t1;
+c
+42
+drop table t1, t2;
+create table t2 (c int, primary key (c));
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+/* 8 */ insert ignore into t1 values (42), (42);
+Warnings:
+Warning	1062	Duplicate entry '42' for key 'PRIMARY'
+select * from t1;
+c
+42
+drop table t1, t2;
+create table t2 (c int, primary key (c));
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "c"';
+/* 9 */ insert ignore into t1 values (42), (42);
+Warnings:
+Warning	1022	Can't write; duplicate key in table 't1'
+select * from t1;
+c
+42
+drop table t1, t2;
+create table t2 (c int, unique key (c));
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "c"';
+/* 9.1 */ insert ignore into t1 values (42), (42);
+Warnings:
+Warning	1062	Duplicate entry '42' for key 'PRIMARY'
+select * from t1;
+c
+42
+drop table t1, t2;
+create table t2 (c int, unique key (c));
+create table t1 (c int, key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "f"';
+/* 10 */ insert ignore into t1 values (42), (42);
+Warnings:
+Warning	1062	Duplicate entry '42' for key 'c'
+select * from t1;
+c
+42
+drop table t1, t2;
+create table t2 (c int, primary key (c));
+create table t1 (c int, key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "blah"';
+/* 11 */ insert ignore into t1 values (42), (42);
+Warnings:
+Warning	1022	Can't write; duplicate key in table 't1'
+select * from t1;
+c
+42
+drop table t1, t2;
+create table t2 (c int, d int, unique key (c), unique key (d));
+create table t1 (c int, d int, key (c), key (d)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "blah"';
+/* 12 */ insert ignore into t1 values (42, 43), (43, 43);
+Warnings:
+Warning	1062	Duplicate entry '43' for key 'd'
+select * from t1;
+c	d
+42	43
+drop table t1, t2;
+# Testing index hint
+create table t2 (c int, d int, primary key (c), key (d));
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c` int(11) NOT NULL,
+  `d` int(11) DEFAULT NULL,
+  PRIMARY KEY (`c`),
+  KEY `d` (`d`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+create table t1 (c int, d int, primary key (c), key (d)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", idx000 "f d"';
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c` int(11) NOT NULL,
+  `d` int(11) DEFAULT NULL,
+  PRIMARY KEY (`c`),
+  KEY `d` (`d`)
+) ENGINE=SPIDER DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", idx000 "f d"'
+/* 13 */ insert into t1 values (42, 23), (37, 93);
+select max(d) from t1;
+max(d)
+93
+drop table t1, t2;
+create table t2 (c int, d int, e int, primary key (c), key (d), unique key (e));
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c` int(11) NOT NULL,
+  `d` int(11) DEFAULT NULL,
+  `e` int(11) DEFAULT NULL,
+  PRIMARY KEY (`c`),
+  UNIQUE KEY `e` (`e`),
+  KEY `d` (`d`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+create table t1 (c int, d int, e int, primary key (c), key (d), unique key (e)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", idx000 "f PRIMARY", idx001 "u d", idx002 "ig e"';
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c` int(11) NOT NULL,
+  `d` int(11) DEFAULT NULL,
+  `e` int(11) DEFAULT NULL,
+  PRIMARY KEY (`c`),
+  UNIQUE KEY `e` (`e`),
+  KEY `d` (`d`)
+) ENGINE=SPIDER DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", idx000 "f PRIMARY", idx001 "u d", idx002 "ig e"'
+/* 14 */ insert into t1 values (42, 23, 89), (37, 93, 47);
+select max(d) from t1;
+max(d)
+93
+drop table t1, t2;
+drop server srv;
+for master_1
+for child2
+for child3
+#
+# end of test mdev_28856
+#

storage/spider/mysql-test/spider/bugfix/t/mdev_28856.test

+--echo #
+--echo # MDEV-28856 Spider: Implement more engine-defined options
+--echo #
+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+# This test covers some table params under consideration for inclusion
+# in the engine-defined options to be implemented in MDEV-28856.
+evalp CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+
+--echo # testing monitoring_*
+INSERT INTO mysql.spider_link_mon_servers
+(db_name, table_name, link_id, sid, server) VALUES
+('test', 't1', '0', 1, 'srv');
+
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", monitoring_kind "2"';
+
+--error 12511
+/* 1 */ insert into t1 values (42);
+--error 12514
+/* 2 */ insert into t1 values (42);
+create table t2 (c int);
+# Even though the table is available now, we still get "all links
+# failed" error
+--error 12514
+/* 3 */ insert into t1 values (42);
+drop table t1, t2;
+
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", monitoring_bg_kind "2",
+         monitoring_bg_interval "500000"';
+
+# The monitoring thread was killed before it could ping the remote
+# table, so the error is not 12511 or 12514
+--error ER_NO_SUCH_TABLE
+/* 4 */ insert into t1 values (42);
+drop table t1;
+
+--echo # testing query_cache_sync
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", query_cache_sync "3"';
+create table t2 (c int);
+/* 5 */ insert into t1 values (42);
+select sql_cache * from t1;
+select sql_no_cache * from t1;
+
+drop table t1, t2;
+
+--echo # testing tgt_pk_names
+# can insert duplicates...
+create table t2 (c int);
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+/* 6 */ insert ignore into t1 values (42), (42);
+select * from t1;
+
+drop table t1, t2;
+
+# pk_names not used because no key declared in t1, 1022
+create table t2 (c int, primary key (c));
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+/* 7 */ insert ignore into t1 values (42), (42);
+select * from t1;
+
+drop table t1, t2;
+
+# pk_name is the default "PRIMARY", 1062
+create table t2 (c int, primary key (c));
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+/* 8 */ insert ignore into t1 values (42), (42);
+select * from t1;
+
+drop table t1, t2;
+
+# key name c does not match PRIMARY, 1022
+create table t2 (c int, primary key (c));
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "c"';
+/* 9 */ insert ignore into t1 values (42), (42);
+select * from t1;
+
+drop table t1, t2;
+
+# local primary key name c matches remote unique key name c, 1062 but
+# warning says PRIMARY instead of c, because key->name is PRIMARY
+# instead of c
+create table t2 (c int, unique key (c));
+create table t1 (c int, primary key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "c"';
+/* 9.1 */ insert ignore into t1 values (42), (42);
+select * from t1;
+
+drop table t1, t2;
+
+# key name f does not match t2 key name, but it is not used any way
+# because there's no primary key, 1062
+create table t2 (c int, unique key (c));
+create table t1 (c int, key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "f"';
+/* 10 */ insert ignore into t1 values (42), (42);
+select * from t1;
+
+drop table t1, t2;
+
+# key name blah does not match t2 error key name PRIMARY, and the
+# non-primary key-route does not return PRIMARY, 1022
+create table t2 (c int, primary key (c));
+create table t1 (c int, key (c)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "blah"';
+/* 11 */ insert ignore into t1 values (42), (42);
+select * from t1;
+
+drop table t1, t2;
+
+# key name blah does not match t2 key name, but still 1062, because we
+# go through the non-primary key route
+create table t2 (c int, d int, unique key (c), unique key (d));
+create table t1 (c int, d int, key (c), key (d)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", pk_name "blah"';
+/* 12 */ insert ignore into t1 values (42, 43), (43, 43);
+select * from t1;
+
+drop table t1, t2;
+
+--echo # Testing index hint
+create table t2 (c int, d int, primary key (c), key (d));
+show create table t2;
+create table t1 (c int, d int, primary key (c), key (d)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", idx000 "f d"';
+show create table t1;
+/* 13 */ insert into t1 values (42, 23), (37, 93);
+select max(d) from t1;
+
+drop table t1, t2;
+
+# multiple indices
+create table t2 (c int, d int, e int, primary key (c), key (d), unique key (e));
+show create table t2;
+create table t1 (c int, d int, e int, primary key (c), key (d), unique key (e)) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", idx000 "f PRIMARY", idx001 "u d", idx002 "ig e"';
+show create table t1;
+/* 14 */ insert into t1 values (42, 23, 89), (37, 93, 47);
+select max(d) from t1;
+
+drop table t1, t2;
+
+drop server srv;
+
+--disable_query_log
+--disable_result_log
+--source ../../t/test_deinit.inc
+--enable_result_log
+--enable_query_log
+--echo #
+--echo # end of test mdev_28856
+--echo #

storage/spider/spd_conn.cc

@@ -1552,6 +1552,11 @@ void spider_conn_set_timeout_from_direct_sql(
   DBUG_VOID_RETURN;
 }
 
+/**
+  Insert a connection to a binary tree ordered by priority
+
+  Starting from `top', find the correct spot for `conn' and insert it.
+*/
 void spider_tree_insert(
   SPIDER_CONN *top,
   SPIDER_CONN *conn
@@ -1589,6 +1594,7 @@ void spider_tree_insert(
   DBUG_VOID_RETURN;
 }
 
+/* Returns the connection with the smallest priority in a tree */
 SPIDER_CONN *spider_tree_first(
   SPIDER_CONN *top
 ) {
@@ -1604,6 +1610,7 @@ SPIDER_CONN *spider_tree_first(
   DBUG_RETURN(current);
 }
 
+/* Returns the connection with the biggest priority in a tree */
 SPIDER_CONN *spider_tree_last(
   SPIDER_CONN *top
 ) {
@@ -1619,6 +1626,12 @@ SPIDER_CONN *spider_tree_last(
   DBUG_RETURN(current);
 }
 
+/*
+  Returns the next connection
+
+  Find the connection in the tree with the smallest priority that is
+  bigger than that of the current connection.
+*/
 SPIDER_CONN *spider_tree_next(
   SPIDER_CONN *current
 ) {

storage/spider/spd_copy_tables.cc

@@ -71,7 +71,7 @@ int spider_udf_set_copy_tables_param_default(
   DBUG_RETURN(0);
 }
 
-#define SPIDER_PARAM_STR_LEN(name) name ## _length
+#define SPIDER_PARAM_LEN(name) name ## _length
 #define SPIDER_PARAM_STR(title_name, param_name)                        \
   if (!strncasecmp(parse.start_title, title_name, title_length))        \
   {                                                                     \
@@ -80,8 +80,7 @@ int spider_udf_set_copy_tables_param_default(
     {                                                                   \
       if ((copy_tables->param_name = spider_create_string(parse.start_value, \
                                                           value_length))) \
-        copy_tables->SPIDER_PARAM_STR_LEN(param_name) = \
-          strlen(copy_tables->param_name); \
+        copy_tables->SPIDER_PARAM_LEN(param_name) = strlen(copy_tables->param_name); \
       else {                                                            \
         error_num= parse.fail(true);                                    \
         goto error;                                                     \

storage/spider/spd_db_conn.cc

@@ -51,12 +51,6 @@ extern SPIDER_DBTON spider_dbton[SPIDER_DBTON_SIZE];
 #define SPIDER_SQL_COALESCE_LEN (sizeof(SPIDER_SQL_COALESCE_STR) - 1)
 #define SPIDER_SQL_HEX_STR "0x"
 #define SPIDER_SQL_HEX_LEN (sizeof(SPIDER_SQL_HEX_STR) - 1)
-#define SPIDER_SQL_SQL_FORCE_IDX_STR " force index("
-#define SPIDER_SQL_SQL_FORCE_IDX_LEN (sizeof(SPIDER_SQL_SQL_FORCE_IDX_STR) - 1)
-#define SPIDER_SQL_SQL_USE_IDX_STR " use index("
-#define SPIDER_SQL_SQL_USE_IDX_LEN (sizeof(SPIDER_SQL_SQL_USE_IDX_STR) - 1)
-#define SPIDER_SQL_SQL_IGNORE_IDX_STR " ignore index("
-#define SPIDER_SQL_SQL_IGNORE_IDX_LEN (sizeof(SPIDER_SQL_SQL_IGNORE_IDX_STR) - 1)
 
 #define SPIDER_SQL_SET_NAMES_STR "set names "
 #define SPIDER_SQL_SET_NAMES_LEN sizeof(SPIDER_SQL_SET_NAMES_STR) - 1
@@ -1484,34 +1478,37 @@ int spider_db_append_key_hint(
   if (hint_str_len >= 2 &&
     (hint_str[0] == 'f' || hint_str[0] == 'F') && hint_str[1] == ' '
   ) {
-    if (str->reserve(hint_str_len - 2 +
-      SPIDER_SQL_SQL_FORCE_IDX_LEN + SPIDER_SQL_CLOSE_PAREN_LEN))
+    if (str->reserve(
+          hint_str_len - 2 + SPIDER_SQL_INDEX_FORCE_LEN +
+          SPIDER_SQL_OPEN_PAREN_LEN + SPIDER_SQL_CLOSE_PAREN_LEN))
       DBUG_RETURN(HA_ERR_OUT_OF_MEM);
     hint_str += 2;
-    str->q_append(SPIDER_SQL_SQL_FORCE_IDX_STR, SPIDER_SQL_SQL_FORCE_IDX_LEN);
+    str->q_append(SPIDER_SQL_INDEX_FORCE_STR, SPIDER_SQL_INDEX_FORCE_LEN);
+    str->q_append(SPIDER_SQL_OPEN_PAREN_STR, SPIDER_SQL_OPEN_PAREN_LEN);
     str->q_append(hint_str, hint_str_len - 2);
     str->q_append(SPIDER_SQL_CLOSE_PAREN_STR, SPIDER_SQL_CLOSE_PAREN_LEN);
   } else if (hint_str_len >= 2 &&
     (hint_str[0] == 'u' || hint_str[0] == 'U') && hint_str[1] == ' '
   ) {
-    if (str->reserve(hint_str_len - 2 +
-      SPIDER_SQL_SQL_USE_IDX_LEN + SPIDER_SQL_CLOSE_PAREN_LEN))
-      DBUG_RETURN(HA_ERR_OUT_OF_MEM);
+    if (str->reserve(
+          hint_str_len - 2 + SPIDER_SQL_INDEX_USE_LEN +
+          SPIDER_SQL_OPEN_PAREN_LEN + SPIDER_SQL_CLOSE_PAREN_LEN))
     hint_str += 2;
-    str->q_append(SPIDER_SQL_SQL_USE_IDX_STR, SPIDER_SQL_SQL_USE_IDX_LEN);
+    str->q_append(SPIDER_SQL_INDEX_USE_STR, SPIDER_SQL_INDEX_USE_LEN);
+    str->q_append(SPIDER_SQL_OPEN_PAREN_STR, SPIDER_SQL_OPEN_PAREN_LEN);
     str->q_append(hint_str, hint_str_len - 2);
     str->q_append(SPIDER_SQL_CLOSE_PAREN_STR, SPIDER_SQL_CLOSE_PAREN_LEN);
   } else if (hint_str_len >= 3 &&
     (hint_str[0] == 'i' || hint_str[0] == 'I') &&
     (hint_str[1] == 'g' || hint_str[1] == 'G') && hint_str[2] == ' '
   ) {
-    if (str->reserve(hint_str_len - 3 +
-      SPIDER_SQL_SQL_IGNORE_IDX_LEN + SPIDER_SQL_CLOSE_PAREN_LEN))
-      DBUG_RETURN(HA_ERR_OUT_OF_MEM);
+    if (str->reserve(
+          hint_str_len - 3 + SPIDER_SQL_INDEX_IGNORE_LEN +
+          SPIDER_SQL_OPEN_PAREN_LEN + SPIDER_SQL_CLOSE_PAREN_LEN))
     hint_str += 3;
-    str->q_append(
-      SPIDER_SQL_SQL_IGNORE_IDX_STR, SPIDER_SQL_SQL_IGNORE_IDX_LEN);
-    str->q_append(hint_str, hint_str_len - 3);
+    str->q_append(SPIDER_SQL_INDEX_IGNORE_STR, SPIDER_SQL_INDEX_IGNORE_LEN);
+    str->q_append(SPIDER_SQL_OPEN_PAREN_STR, SPIDER_SQL_OPEN_PAREN_LEN);
+    str->q_append(hint_str, hint_str_len - 2);
     str->q_append(SPIDER_SQL_CLOSE_PAREN_STR, SPIDER_SQL_CLOSE_PAREN_LEN);
   } else if (str->reserve(hint_str_len + SPIDER_SQL_SPACE_LEN))
     DBUG_RETURN(HA_ERR_OUT_OF_MEM);

storage/spider/spd_direct_sql.cc

@@ -814,7 +814,7 @@ int spider_udf_direct_sql_get_server(
   DBUG_RETURN(error_num);
 }
 
-#define SPIDER_PARAM_STR_LEN(name) name ## _length
+#define SPIDER_PARAM_LEN(name) name ## _length
 #define SPIDER_PARAM_STR(title_name, param_name)                        \
   if (!strncasecmp(parse.start_title, title_name, title_length))        \
   {                                                                     \
@@ -823,7 +823,7 @@ int spider_udf_direct_sql_get_server(
     {                                                                   \
       if ((direct_sql->param_name = spider_create_string(parse.start_value, \
                                                          value_length))) \
-        direct_sql->SPIDER_PARAM_STR_LEN(param_name) = strlen(direct_sql->param_name); \
+        direct_sql->SPIDER_PARAM_LEN(param_name) = strlen(direct_sql->param_name); \
       else {                                                            \
         error_num= parse.fail(true);                                    \
         goto error;                                                     \

storage/spider/spd_include.h

@@ -364,9 +364,18 @@ typedef struct st_spider_conn
   THD                *thd;
   void               *another_ha_first;
   void               *another_ha_last;
+  /* Exactly one of p_small and p_big is not null */
+  /* The parent node in the binary tree ordered by priority with a
+  smaller or equal priority */
   st_spider_conn     *p_small;
+  /* The parent node in the binary tree ordered by priority with a
+  bigger priority */
   st_spider_conn     *p_big;
+  /* The child node in the binary tree ordered by priority with a
+  smaller priority */
   st_spider_conn     *c_small;
+  /* The child node in the binary tree ordered by priority with a
+  bigger or equal priority */
   st_spider_conn     *c_big;
   longlong           priority;
   bool               server_lost;

storage/spider/spd_table.cc

@@ -1595,7 +1595,9 @@ static int spider_set_ll_value(
   DBUG_RETURN(error_num);
 }
 
-#define SPIDER_PARAM_STR_LEN(name) name ## _length
+#define SPIDER_PARAM_LEN(name) name ## _length
+#define SPIDER_PARAM_LENS(name) name ## _lengths
+#define SPIDER_PARAM_CHARLEN(name) name ## _charlen
 #define SPIDER_PARAM_STR(title_name, param_name)                        \
   if (!strncasecmp(parse.start_title, title_name, title_length))        \
   {                                                                     \
@@ -1604,7 +1606,7 @@ static int spider_set_ll_value(
     {                                                                   \
       if ((share->param_name = spider_create_string(parse.start_value,  \
                                                     value_length)))     \
-        share->SPIDER_PARAM_STR_LEN(param_name) = strlen(share->param_name); \
+        share->SPIDER_PARAM_LEN(param_name) = strlen(share->param_name); \
       else {                                                            \
         error_num= parse.fail(true);                                    \
         goto error;                                                     \
@@ -1613,8 +1615,6 @@ static int spider_set_ll_value(
     } \
     break; \
   }
-#define SPIDER_PARAM_STR_LENS(name) name ## _lengths
-#define SPIDER_PARAM_STR_CHARLEN(name) name ## _charlen
 #define SPIDER_PARAM_STR_LIST(title_name, param_name)         \
   SPIDER_PARAM_STR_LIST_CHECK(title_name, param_name, FALSE)
 #define SPIDER_PARAM_STR_LIST_CHECK(title_name, param_name, already_set) \
@@ -1628,16 +1628,16 @@ static int spider_set_ll_value(
     }                                                                   \
     if (!share->param_name)                                             \
     {                                                                   \
-      share->SPIDER_PARAM_STR_CHARLEN(param_name)= value_length;        \
+      share->SPIDER_PARAM_CHARLEN(param_name)= value_length;            \
       if ((error_num= spider_create_string_list(                        \
              &share->param_name,                                        \
-             &share->SPIDER_PARAM_STR_LENS(param_name),                 \
-             &share->SPIDER_PARAM_STR_LEN(param_name),                  \
+             &share->SPIDER_PARAM_LENS(param_name),                     \
+             &share->SPIDER_PARAM_LEN(param_name),                      \
              parse.start_value,                                         \
-             share->SPIDER_PARAM_STR_CHARLEN(param_name))))             \
+             share->SPIDER_PARAM_CHARLEN(param_name))))                 \
         goto error;                                                     \
       THD *thd= current_thd;                                            \
-      if (share->SPIDER_PARAM_STR_LEN(param_name) > 1 && create_table)  \
+      if (share->SPIDER_PARAM_LEN(param_name) > 1 && create_table)      \
       {                                                                 \
         push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,        \
                             HA_ERR_UNSUPPORTED,                         \
@@ -1703,7 +1703,6 @@ static int spider_set_ll_value(
     } \
     break; \
   }
-#define SPIDER_PARAM_LONG_LEN(name) name ## _length
 #define SPIDER_PARAM_LONG_LIST_WITH_MAX(title_name, param_name,   \
                                         min_val, max_val)         \
   if (!strncasecmp(parse.start_title, title_name, title_length))  \
@@ -1713,7 +1712,7 @@ static int spider_set_ll_value(
     {                                                             \
       if ((error_num = spider_create_long_list(                   \
              &share->param_name,                                  \
-             &share->SPIDER_PARAM_LONG_LEN(param_name), \
+             &share->SPIDER_PARAM_LEN(param_name),                \
              parse.start_value,                                   \
              value_length,                                        \
              min_val, max_val)))                                  \
@@ -1721,7 +1720,6 @@ static int spider_set_ll_value(
     }                                                             \
     break;                                                        \
   }
-#define SPIDER_PARAM_LONGLONG_LEN(name) name ## _length
 #define SPIDER_PARAM_LONGLONG_LIST_WITH_MAX(title_name, param_name, \
                                             min_val, max_val)       \
   if (!strncasecmp(parse.start_title, title_name, title_length))    \
@@ -1731,7 +1729,7 @@ static int spider_set_ll_value(
     {                                                               \
       if ((error_num = spider_create_longlong_list(                 \
              &share->param_name,                                    \
-             &share->SPIDER_PARAM_LONGLONG_LEN(param_name), \
+             &share->SPIDER_PARAM_LEN(param_name),                  \
              parse.start_value,                                     \
              value_length,                                          \
              min_val, max_val)))                                    \
@@ -1808,21 +1806,25 @@ static int spider_set_ll_value(
 /*
   Set a given engine-defined option, which holds a string list, to the
   corresponding attribute of SPIDER_SHARE.
-*/
+  */
 #define SPIDER_OPTION_STR_LIST(title_name, option_name, param_name)   \
   if (option_struct && option_struct->option_name)                    \
   {                                                                   \
     DBUG_PRINT("info", ("spider " title_name " start overwrite"));    \
-    share->SPIDER_PARAM_STR_CHARLEN(param_name)=                        \
+    share->SPIDER_PARAM_CHARLEN(param_name)=                          \
       strlen(option_struct->option_name);                             \
     if ((error_num= spider_create_string_list(                        \
-           &share->param_name, &share->SPIDER_PARAM_STR_LENS(param_name), \
-           &share->SPIDER_PARAM_STR_LEN(param_name),                    \
+           &share->param_name, &share->SPIDER_PARAM_LENS(param_name), \
+           &share->SPIDER_PARAM_LEN(param_name),                      \
            option_struct->option_name,                                \
-           share->SPIDER_PARAM_STR_CHARLEN(param_name))))               \
+           share->SPIDER_PARAM_CHARLEN(param_name))))                 \
       goto error;                                                     \
   }
 
+/**
+  Assign -1 to some `SPIDER_SHARE' numeric fields, to indicate they
+  have not been specified by the user yet.
+*/
 static void spider_minus_1(SPIDER_SHARE *share, TABLE_SHARE *table_share)
 {
   share->sts_bg_mode = -1;
@@ -2160,6 +2162,8 @@ int spider_parse_connect_info(
     ("spider s->normalized_path=%s", table_share->normalized_path.str));
   spider_get_partition_info(share->table_name, share->table_name_length,
     table_share, part_info, &part_elem, &sub_elem);
+  /* Find the correct table options, depending on if we are parsing a
+  table, a partition, or a sub-partition. */
   if (part_info)
     if (part_info->is_sub_partitioned())
       option_struct= sub_elem->option_struct;
@@ -2176,6 +2180,7 @@ int spider_parse_connect_info(
       connect_string = NULL;
     }
 
+    /* Get the correct connect info for the current level. */
     int error_num_1 = spider_get_connect_info(i, part_elem, sub_elem,
                                               table_share, connect_string);
     if (error_num_1 == 1)
@@ -3168,7 +3173,7 @@ int spider_parse_connect_info(
       {
         if (
           spider_dbton[roop_count2].wrapper &&
-          !strcmp(share->tgt_wrappers[roop_count],
+          !strcasecmp(share->tgt_wrappers[roop_count],
             spider_dbton[roop_count2].wrapper)
         ) {
           break;
@@ -4002,7 +4007,7 @@ int spider_create_conn_keys(
           spider_dbton[dbton_idx].wrapper : "NULL"));
       if (
         spider_dbton[dbton_idx].wrapper &&
-        !strcmp(share->tgt_wrappers[all_link_idx],
+        !strcasecmp(share->tgt_wrappers[all_link_idx],
           spider_dbton[dbton_idx].wrapper)
       ) {
         spider_set_bit(share->dbton_bitmap, dbton_idx);