From 6b8d34fe0d5e73a469383bcb0818d3ff91ed9a84 Mon Sep 17 00:00:00 2001
From: Alexey Botchkov <holyfoot@askmonty.org>
Date: Tue, 12 Jun 2018 12:36:51 +0400
Subject: [PATCH] MDEV-14668 ADD PRIMARY KEY IF NOT EXISTS on composite key.

Check the name of the primary key to be 'PRIMARY'. Than
differs it from any implicit primary keys created by an engine.
---
 mysql-test/r/alter_table.result | 23 +++++++++++++++++++++++
 mysql-test/t/alter_table.test   | 16 ++++++++++++++++
 sql/sql_table.cc                |  4 +++-
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/mysql-test/r/alter_table.result b/mysql-test/r/alter_table.result
index bb78df907ad..c6e3c7e31d9 100644
--- a/mysql-test/r/alter_table.result
+++ b/mysql-test/r/alter_table.result
@@ -2225,3 +2225,26 @@ t1	CREATE TABLE `t1` (
   `b` int(11) DEFAULT NULL
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 DROP TABLE t1;
+#
+# MDEV-14668 ADD PRIMARY KEY IF NOT EXISTS on composite key
+#
+CREATE TABLE t1 (
+`ID` BIGINT(20) NOT NULL,
+`RANK` MEDIUMINT(4) NOT NULL,
+`CHECK_POINT` BIGINT(20) NOT NULL,
+UNIQUE INDEX `HORIZON_UIDX01` (`ID`, `RANK`)
+) ENGINE=InnoDB;
+ALTER TABLE t1 ADD PRIMARY KEY IF NOT EXISTS (`ID`, `CHECK_POINT`);
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `ID` bigint(20) NOT NULL,
+  `RANK` mediumint(4) NOT NULL,
+  `CHECK_POINT` bigint(20) NOT NULL,
+  PRIMARY KEY (`ID`,`CHECK_POINT`),
+  UNIQUE KEY `HORIZON_UIDX01` (`ID`,`RANK`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+ALTER TABLE t1 ADD PRIMARY KEY IF NOT EXISTS (`ID`, `CHECK_POINT`);
+Warnings:
+Note	1061	Multiple primary key defined
+DROP TABLE t1;
diff --git a/mysql-test/t/alter_table.test b/mysql-test/t/alter_table.test
index 585a272de9b..28d8c5bf5e9 100644
--- a/mysql-test/t/alter_table.test
+++ b/mysql-test/t/alter_table.test
@@ -1841,3 +1841,19 @@ CREATE TABLE t1 (a INT, b INT) ENGINE=InnoDB;
 ALTER TABLE t1 DROP INDEX IF EXISTS fk, DROP COLUMN IF EXISTS c;
 SHOW CREATE TABLE t1;
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-14668 ADD PRIMARY KEY IF NOT EXISTS on composite key
+--echo #
+CREATE TABLE t1 (
+        `ID` BIGINT(20) NOT NULL,
+            `RANK` MEDIUMINT(4) NOT NULL,
+                `CHECK_POINT` BIGINT(20) NOT NULL,
+                    UNIQUE INDEX `HORIZON_UIDX01` (`ID`, `RANK`)
+    ) ENGINE=InnoDB;
+
+ALTER TABLE t1 ADD PRIMARY KEY IF NOT EXISTS (`ID`, `CHECK_POINT`);
+SHOW CREATE TABLE t1;
+ALTER TABLE t1 ADD PRIMARY KEY IF NOT EXISTS (`ID`, `CHECK_POINT`);
+DROP TABLE t1;
+
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 376c1362cc7..6c71067d51b 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -5930,7 +5930,9 @@ drop_create_field:
 
       /* Check if the table already has a PRIMARY KEY */
       if (key->type == Key::PRIMARY &&
-          table->s->primary_key != MAX_KEY)
+          table->s->primary_key != MAX_KEY &&
+          (keyname=  table->s->key_info[table->s->primary_key].name) &&
+          my_strcasecmp(system_charset_info, keyname, primary_key_name) == 0)
       {
         push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
             ER_DUP_KEYNAME, ER(ER_MULTIPLE_PRI_KEY));