Merge lp:~akopytov/percona-server/bug915814-5.5 into lp:percona-server/5.5

[Alexey Kopytov]

[Alexey Kopytov (akopytov)]

http://jenkins.percona.com/view/Percona%20Server%205.5/job/percona-server-5.5-param/303/

[Alexey Kopytov (akopytov)]

There was another problem with the old patch that was caught by Jenkins. Link for the fixed version: http://jenkins.percona.com/view/Percona%20Server%205.5/job/percona-server-5.5-param/305/

[Laurynas Biveinis (laurynas-biveinis)]

I'd prefer to have a #define or enum constant for the query buffer length, together with the layout-explaining comment, instead of two separate copies at around diff lines 348 and 942.

review: Needs Fixing

[Alexey Kopytov (akopytov)]

On 25.03.12 14:16, Laurynas Biveinis wrote:
> I'd prefer to have a #define or enum constant for the query buffer length

Done.
http://jenkins.percona.com/view/Percona%20Server%205.5/job/percona-server-5.5-param/306/

[Laurynas Biveinis (laurynas-biveinis)]

review: Approve

=== modified file 'patches/query_cache_enhance.patch'
--- patches/query_cache_enhance.patch	2012-02-02 07:11:59 +0000
+++ patches/query_cache_enhance.patch	2012-03-25 11:37:19 +0000
@@ -1,4 +1,4 @@
-# name       : query_cache_enhance.patch
+# name       : query_cache_with_comments.patch
 # introduced : 11 or before
 # maintainer : Oleg
 #
@@ -25,7 +25,7 @@
 +2010-11 - Ported to 5.5
 --- a/sql/mysqld.cc
 +++ b/sql/mysqld.cc
-@@ -909,6 +909,7 @@
+@@ -915,6 +915,7 @@
  #endif
  #ifdef HAVE_QUERY_CACHE
  ulong query_cache_min_res_unit= QUERY_CACHE_MIN_RESULT_DATA_SIZE;
@@ -43,510 +43,252 @@
  extern ulonglong log_output_options;
  extern ulong log_backup_output_options;
  extern my_bool opt_log_queries_not_using_indexes;
+--- /dev/null
++++ b/sql/query_strip_comments.h
+@@ -0,0 +1,37 @@
++#ifndef _SQL_QUERY_STRIPC_COMMENTS_H_
++#define _SQL_QUERY_STRIPC_COMMENTS_H_
++#ifdef HAVE_QUERY_CACHE
++
++// implemented in sql_cache.cc
++class QueryStripComments
++{
++private:
++  QueryStripComments(const QueryStripComments&);
++  QueryStripComments& operator=(const QueryStripComments&);
++public:
++  QueryStripComments();
++  ~QueryStripComments();
++  void set(const char* a_query, uint a_query_length, uint a_additional_length);
++  
++  char* query()        { return buffer; }
++  uint  query_length() { return length; }
++private:
++  void cleanup();
++private:
++  char* buffer;
++  uint  length /*query length, not buffer length*/;
++  uint  buffer_length;
++};
++class QueryStripComments_Backup
++{
++public:
++  QueryStripComments_Backup(THD* a_thd,QueryStripComments* qsc);
++  ~QueryStripComments_Backup();
++private:
++  THD*  thd;
++  char* query;
++  uint  length;
++};
++
++#endif // HAVE_QUERY_CACHE
++#endif // _SQL_QUERY_STRIPC_COMMENTS_H_
 --- a/sql/sql_cache.cc
 +++ b/sql/sql_cache.cc
-@@ -344,6 +344,496 @@
+@@ -344,6 +344,198 @@
  #include "probes_mysql.h"
  #include "transaction.h"
  
-+
-+namespace query_comments_parser
-+{
-+
-+
-+enum Kind
-+{
-+  /* 'Empty' symbol - epsilon in classic parsers */
-+  Empty,
-+  /*
-+    Special symbols:
-+      * exclamation comment: slash-star-exclamation comment-body star-slash
-+      * single-line and multi-line comments
-+  */
-+  Special,
-+  /* Whitespaces: ' ' \t \r \n */
-+  WhiteSpace,
-+  /*
-+    1) C-style comment (slash-star comment-body star-slash)
-+    2) signle-line comment:
-+      * sharp comment (sharp comment-body new-line)
-+      * minus-minus comment (minus-minus comment-body new-line)
-+  */
-+  Comment,
-+  /* Not a special symbols (this symbols can't be before SELECT ). */
-+  Another,
-+  /* Error: not-closed quotes, not-closed C-style comment, end-of-query */
-+  Error
-+};
-+
-+
-+/**
-+  Analyze kind of prefix of input string.
-+
-+  @param where pointer to pointer to begin of string. After analyzing input
-+  string function skip analyzed prefix and return pointer to the next part
-+  of string in the @param where.
-+
-+  @return kind of analyzed prefix.
++#include "query_strip_comments.h"
++
++/*
++  Number of bytes to be allocated in a query cache buffer in addition to the
++  query string length.
++
++  The query buffer layout is:
++
++  buffer :==
++    <statement>   The input statement(s)
++    '\0'          Terminating null char
++    <db_length>   Length of following current database name (size_t)
++    <db_name>     Name of current database
++    <flags>       Flags struct
 +*/
-+static Kind analyze(const char **where, const char *const end)
-+{
-+  DBUG_ASSERT(where != NULL);
-+  DBUG_ASSERT(*where != NULL);
-+  const char*&to= *where;
-+  /* if empty */
-+  if (*to == '\0')
-+  {
-+    return Empty;
-+  }
-+
-+  /* current symbol */
-+  char current= *to;
-+
-+  switch (current)
-+  {
-+  case '\'':
-+  case '"':
-+    /* skip quote */
-+    to++;
-+    /* search pair */
-+    while (true)
++#define QUERY_BUFFER_ADDITIONAL_LENGTH(db_length)               \
++  (1 + sizeof(size_t) + db_length + QUERY_CACHE_FLAGS_SIZE)
++
++QueryStripComments::QueryStripComments()
++{
++  buffer = 0;
++  length = 0;
++  buffer_length = 0;
++}
++QueryStripComments::~QueryStripComments()
++{
++  cleanup();
++}
++
++inline bool query_strip_comments_is_white_space(char c)
++{
++  return ((' ' == c) || ('\t' == c) || ('\r' == c) || ('\n' ==c ));
++}
++void QueryStripComments::set(const char* query, uint query_length, uint additional_length)
++{
++  uint new_buffer_length = query_length + additional_length;
++  if(new_buffer_length > buffer_length)
++  {
++    cleanup();
++    buffer = (char*)my_malloc(new_buffer_length,MYF(0));
++  }
++  uint query_position = 0;
++  uint position = 0;
++  // Skip whitespaces from begin
++  while((query_position < query_length) && query_strip_comments_is_white_space(query[query_position]))
++  {
++    ++query_position;
++  }
++  long int last_space = -1;
++  while(query_position < query_length)
++  {
++    char current = query[query_position];
++    bool insert_space = false; // insert space to buffer, (IMPORTANT) don't update query_position
++    switch(current)
 +    {
-+      /* check for pair of quote */
-+      if (*to == current)
-+      {
-+        /* skip second quote */
-+        to++;
-+        /* check for same symbol after second quote */
-+        if (to < end && *to == current)
-+        {
-+          /* same symbol, skip it */
-+          to++;
-+          /* check for end-of-line */
-+          if (to == end)
-+          {
-+            /* not found - not closed quote */
-+            return Error;
-+          }
-+          else
-+          {
-+            /* continue search of pair */
++    case '\'':
++    case '"':
++      {
++        buffer[position++] = query[query_position++]; // copy current symbol
++        while(query_position < query_length)
++        {
++          if(current == query[query_position]) // found pair quote
++          {
++            break;
++          }
++          buffer[position++] = query[query_position++]; // copy current symbol
++        }
++        break;
++      }
++    case '/':
++      {
++        if(((query_position + 2) < query_length) && ('*' == query[query_position+1]) && ('!' != query[query_position+2]))
++        {
++          query_position += 2; // skip "/*"
++          do
++          {
++            if('*' == query[query_position] && '/' == query[query_position+1]) // check for "*/"
++            {
++              query_position += 2; // skip "*/"
++              insert_space = true;
++              break;
++            }
++            else
++            {
++              ++query_position;
++            }
++          }
++          while(query_position < query_length);
++          if(!insert_space)
++          {
 +            continue;
 +          }
 +        }
-+        else
-+        {
-+          return Another;
-+        }
-+      }
-+      /* check for escaped symbols */
-+      if (*to == '\\')
-+      {
-+        /* backslash, skip it */
-+        to++;
-+      }
-+      /* check for end-of-line */
-+      if (to == end)
-+      {
-+        /* not found - not closed quote */
-+        return Error;
-+      }
-+      /* skip current symbol */
-+      to++;
-+    }
-+  case '-':
-+    /* Skip minus */
-+    to++;
-+    /* Check for second minus */
-+    if (*to != '-')
-+    {
-+      /* Just minus */
-+      return Another;
-+    }
-+    else
-+    {
-+      /*
-+        Prefix is  minus-minus, next case-branch is processing
-+        single line comments.
-+      */
-+    }
-+  case '#':
-+    /*
-+      This is single-line comment, it started by "#" or "--".
-+      Skip first symbol.
-+    */
-+    to++;
-+    /* search new-line */
-+    to= strchr(to, '\n');
-+    if (NULL == to)
-+    {
-+      /* not found, end of the comment is the end of the query */
-+      to= end;
-+    }
-+    else
-+    {
-+      /* skip end-of-line */
-+      to++;
-+    }
-+    return Comment;
-+  case '/':
-+    /* skip slash */
-+    to++;
-+    /* check for star */
-+    if (*to == '*')
-+    {
-+      /* skip star */
-+      to++;
-+      /* check for exclamation */
-+      bool exclamation= (*to == '!');
-+      /* search star-slash */
-+      to= strstr(to, "*/");
-+      if (NULL == to)
-+      {
-+        /* not found - not closed comment */
-+        return Error;
-+      }
-+      else
-+      {
-+        /* found */
-+        DBUG_ASSERT(to + 1 < end);
-+        DBUG_ASSERT(0 == strncmp(to, "*/", 2));
-+        /* skip star-slash */
-+        to++;
-+        to++;
-+        return (exclamation ? Special : Comment);
-+      }
-+    }
-+    else
-+    {
-+      /* just slash */
-+      return Another;
-+    }
-+  case ' ':
-+  case '\t':
-+  case '\r':
-+  case '\n':
-+    {
-+      /* skip space */
-+      to++;
-+      return WhiteSpace;
-+    }
-+  case '\\':
-+    {
-+      /* skip backslash */
-+      to++;
-+      if (to == end)
-+      {
-+        /*
-+          query complete by backslash
-+          probable error?
-+        */
-+        return Another;
-+      }
-+      else
-+      {
-+        /* skip after backslash symbol */
-+        to++;
-+        return Another;
-+      }
-+    }
-+  case '(':
-+  case ')':
-+    {
-+      /* skip parenthese */
-+      to++;
-+      return Special;
-+    }
-+  default:
-+    {
-+      /* skip symbol */
-+      to++;
-+      return Another;
-+    }
-+  };
-+}
-+
-+
-+static bool remove_comments_from_query(const char *const query,
-+                                       const size_t       query_length,
-+                                       char       *const result,
-+                                       size_t            *result_length)
-+{
-+  /* pointer to begin of parsed block */
-+  const char *from=  query;
-+  const char *to=    query;
-+  /* pointer to end of the query */
-+  const char *const end= query + query_length;
-+  /* pointer to last space */
-+  const char *space= NULL;
-+  /* current position in result buffer */
-+  char *current= result;
-+  while (true)
-+  {
-+    from= to;
-+    switch (analyze(&to, end))
-+    {
-+    case Empty:
-+      {
-+        /*
-+          parse completed
-+          check for whitespace in the end
-+        */
-+        if (current == space)
-+        {
-+          /* drop whitespace in the end of query */
-+          --current;
-+        }
-+        /* result is null-terminated string */
-+        *current= 0;
-+        /* set result length */
-+        *result_length= current - result;
-+        /* all right */
-+        return true;
-+      }
-+    case Comment:
-+      /* should just insert space instead of comment */
-+    case WhiteSpace:
-+      if (space == current || from == query)
-+      {
-+        /* previous symbol was space */
-+      }
-+      else
-+      {
-+        /* insert space to result buffer */
-+        *current= ' ';
-+        /* switch after inserted space */
-+        current++;
-+      }
-+      /* remember last-after-space position */
-+      space= current;
-+      /* parse again */
-+      continue;
-+    case Special:
-+    case Another:
-+      {
-+        /* calculate parsed block size */
-+        size_t block_size= to - from;
-+        /* copy parsed block to result */
-+        memcpy(current, from, block_size);
-+        /* switch result after copied block */
-+        current+= block_size;
-+        /* switch after parsed block */
-+        from= to;
-+        /* parse again */
-+        continue;
-+      }
-+    case Error:
-+    default:
-+      {
-+        /* bad source query */
-+        return false;
-+      }
-+    }
-+  }
-+}
-+
-+
-+static size_t skip_not_another(const char *const query, size_t query_length)
-+{
-+  const char *from= query;
-+  const char *to=   query;
-+  const char *const end= query + query_length;
-+  while (true)
-+  {
-+    switch (analyze(&to, end))
-+    {
-+    case Error:
-+      return 0;
-+    case Empty:
-+    case Another:
-+      return (from - query);
-+    default:
-+      from= to;
-+      continue;
-+    };
-+  }
-+}
-+
-+
-+static size_t skip_default(const char *const query, size_t /* query_length */)
-+{
-+  size_t query_position= 0;
-+  /*
-+    Skip '(' characters in queries like following:
-+    (select a from t1) union (select a from t1);
-+  */
-+  while (query[query_position]=='(')
-+    query_position++;
-+  return query_position;
-+}
-+
-+
-+} /* namespace query_comments_parser */
-+
-+class Query_Switcher
-+{
-+private:
-+  Query_Switcher(const Query_Switcher&);
-+  Query_Switcher& operator=(const Query_Switcher&);
-+
-+
-+public:
-+  Query_Switcher(THD *thd) :
-+    target_query(&(thd_query_string(thd)->str)),
-+    target_length(&(thd_query_string(thd)->length)),
-+    backup_query(thd->query()),
-+    backup_length(thd->query_length())
-+  {
-+  }
-+
-+  Query_Switcher(char   **query,
-+                 size_t  *length) :
-+    target_query(query),
-+    target_length(length),
-+    backup_query(*query),
-+    backup_length(*length)
-+  {
-+  }
-+public:
-+  void replace(Query_Without_Comments *query_without_comments)
-+  {
-+    *target_query=  query_without_comments->query();
-+    *target_length= query_without_comments->length();
-+  }
-+  void restore()
-+  {
-+    *target_query=  backup_query;
-+    *target_length= backup_length;
-+  }
-+private:
-+  char*  *target_query;
-+  size_t *target_length;
-+public:
-+  char *const  backup_query;
-+  size_t const backup_length;
-+};
-+
-+class Comments_Processor
-+{
-+private:
-+  Comments_Processor(const Comments_Processor&);
-+  Comments_Processor& operator=(const Comments_Processor&);
-+
-+
-+public:
-+  Comments_Processor(THD *thd) :
-+    query_switcher        (thd),
-+    db_length             (thd->db_length),
-+    query_without_comments(&(thd->query_without_comments)),
-+    enabled               (opt_query_cache_strip_comments),
-+    restore               (false)
-+  {
-+  }
-+
-+
-+  Comments_Processor(Query_Without_Comments *current_query_without_comments,
-+                     char                  **query,
-+                     size_t                 *length,
-+                     const size_t            current_db_length) :
-+    query_switcher        (query, length),
-+    db_length             (current_db_length),
-+    query_without_comments(current_query_without_comments),
-+    enabled               (opt_query_cache_strip_comments),
-+    restore               (false)
-+  {
-+  }
-+
-+
-+  ~Comments_Processor()
-+  {
-+    restore_comments();
-+  }
-+
-+
-+  size_t prefix_length()
-+  {
-+    using query_comments_parser::skip_not_another;
-+    using query_comments_parser::skip_default;
-+    if (enabled)
-+    {
-+      return skip_not_another(query_switcher.backup_query,
-+                              query_switcher.backup_length);
-+    }
-+    else
-+    {
-+      return skip_default(query_switcher.backup_query,
-+                          query_switcher.backup_length);
-+    }
-+  }
-+
-+
-+  bool remove_comments()
-+  {
-+    if (!enabled || restore)
-+    {
-+      return true;
-+    }
-+    /* Allocate memory for query rewrite */
-+    if (!query_without_comments->allocate(query_switcher.backup_length,
-+                                          db_length))
-+    {
-+      return false;
-+    }
-+    /* Remove comment from query */
-+    size_t result_length;
-+    using query_comments_parser::remove_comments_from_query;
-+    if (!(restore= remove_comments_from_query(query_switcher.backup_query,
-+                                              query_switcher.backup_length,
-+                                              query_without_comments->query(),
-+                                              &result_length)))
-+    {
-+      return false;
-+    }
-+    query_without_comments->set_length(result_length);
-+    size_t db_length_from_query=
-+        *((size_t*)(query_switcher.backup_query +
-+                    query_switcher.backup_length + 1));
-+    *((size_t*)(query_without_comments->query() +
-+                result_length + 1))= db_length_from_query;
-+    /* Replace original query by striped */
-+    query_switcher.replace(query_without_comments);
-+    return restore;
-+  }
-+
-+
-+  void restore_comments()
-+  {
-+    if (enabled && restore)
-+    {
-+      /* Replace striped query by original */
-+      query_switcher.restore();
-+
-+      /* Clean query_without_comments */
-+      query_without_comments->set_length(0);
-+
-+      /* Mark as restored */
-+      restore= false;
-+    }
-+  }
-+private:
-+  Query_Switcher query_switcher;
-+private:
-+  const size_t db_length;
-+private:
-+  Query_Without_Comments *query_without_comments;
-+  bool                    enabled;
-+  bool                    restore;
-+};
++        break;
++      }
++    case '-':
++      {
++        if(query[query_position+1] == '-')
++        {
++          ++query_position; // skip "-", and go to search of "\n"
++        }
++        else
++        {
++          break;
++        }
++      }
++    case '#':
++      {
++        do
++        {
++          ++query_position; // skip current symbol (# or -)
++          if('\n' == query[query_position])  // check for '\n'
++          {
++            ++query_position; // skip '\n'
++            insert_space = true;
++            break;
++          }
++        }
++        while(query_position < query_length);
++        if(insert_space)
++        {
++          break;
++        }
++        else
++        {
++          continue;
++        }
++      }
++    default:
++      if(query_strip_comments_is_white_space(current))
++      {
++        insert_space = true;
++        ++query_position;
++      }
++      break; // make gcc happy
++    }
++    if(insert_space)
++    {
++      if((uint) (last_space + 1) != position)
++      {
++        last_space = position;
++        buffer[position++] = ' ';
++      }
++    }
++    else if (query_position < query_length)
++    {
++      buffer[position++] = query[query_position++];
++    }
++  }
++  while((0 < position) && query_strip_comments_is_white_space(buffer[position - 1]))
++  {
++    --position;
++  }
++  buffer[position] = 0;
++  length = position;
++}
++void QueryStripComments::cleanup()
++{
++  if(buffer)
++  {
++    my_free(buffer);
++  }
++  buffer        = 0;
++  length        = 0;
++  buffer_length = 0;
++}
++QueryStripComments_Backup::QueryStripComments_Backup(THD* a_thd,QueryStripComments* qsc)
++{
++  if(opt_query_cache_strip_comments)
++  {
++    thd = a_thd;
++    query = thd->query();
++    length = thd->query_length();
++    qsc->set(query, length, QUERY_BUFFER_ADDITIONAL_LENGTH(thd->db_length));
++    *(size_t *) (qsc->query() + qsc->query_length() + 1)= thd->db_length;
++    thd->set_query(qsc->query(),qsc->query_length());
++  }
++  else
++  {
++    thd = 0;
++    query = 0;
++    length = 0;
++  }
++}
++QueryStripComments_Backup::~QueryStripComments_Backup()
++{
++  if(thd)
++  {
++    thd->set_query(query,length);
++  }
++}
 +
  #ifdef EMBEDDED_LIBRARY
  #include "emb_qcache.h"
  #endif
-@@ -454,7 +944,12 @@
+@@ -454,7 +646,12 @@
    Query_cache_wait_state wait_state(thd, __func__, __FILE__, __LINE__);
    DBUG_ENTER("Query_cache::try_lock");
  
-+  const char *old_proc_info= thd->proc_info;
++  const char* old_proc_info= thd->proc_info;
 +  thd_proc_info(thd,"Waiting on query cache mutex");
 +  DEBUG_SYNC(thd, "before_query_cache_mutex");
    mysql_mutex_lock(&structure_guard_mutex);
@@ -555,171 +297,191 @@
    while (1)
    {
      if (m_cache_lock_status == Query_cache::UNLOCKED)
-@@ -1274,6 +1769,8 @@
+@@ -1274,6 +1471,8 @@
        unlock();
        DBUG_VOID_RETURN;
      }
-+    Comments_Processor comments_processor(thd);
-+    comments_processor.remove_comments();
++    QueryStripComments *query_strip_comments = &(thd->query_strip_comments);
++    QueryStripComments_Backup backup(thd,query_strip_comments);
  
      /* Key is query + database + flag */
      if (thd->db_length)
-@@ -1440,7 +1937,7 @@
- */
- 
- int
--Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length)
-+Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length_uint)
- {
-   ulonglong engine_data;
-   Query_cache_query *query;
-@@ -1452,6 +1949,11 @@
+@@ -1451,6 +1650,9 @@
+   Query_cache_block_table *block_table, *block_table_end;
    ulong tot_length;
    Query_cache_query_flags flags;
++  QueryStripComments *query_strip_comments = &(thd->query_strip_comments);
++  char *sql_backup          = sql;
++  uint  query_length_backup = query_length;
    DBUG_ENTER("Query_cache::send_result_to_client");
-+  size_t query_length= query_length_uint;
-+  Comments_Processor comments_processor(&(thd->query_without_comments),
-+                                        &sql,
-+                                        &query_length,
-+                                        thd->db_length);
  
    /*
-     Testing 'query_cache_size' without a lock here is safe: the thing
-@@ -1471,13 +1973,7 @@
-   }
+@@ -1472,21 +1674,103 @@
  
    {
--    uint i= 0;
+     uint i= 0;
 -    /*
 -      Skip '(' characters in queries like following:
 -      (select a from t1) union (select a from t1);
 -    */
 -    while (sql[i]=='(')
 -      i++;
-+    size_t i= comments_processor.prefix_length();
- 
-     /*
-       Test if the query is a SELECT
-@@ -1487,10 +1983,11 @@
-       frequently appeared in real life, consequently we can
-       check all such queries, too.
-     */
--    if ((my_toupper(system_charset_info, sql[i])     != 'S' ||
--         my_toupper(system_charset_info, sql[i + 1]) != 'E' ||
--         my_toupper(system_charset_info, sql[i + 2]) != 'L') &&
--        sql[i] != '/')
-+    if (!((i + 2 < query_length) &&
-+          ((my_toupper(system_charset_info, sql[i])     == 'S' &&
-+            my_toupper(system_charset_info, sql[i + 1]) == 'E' &&
-+            my_toupper(system_charset_info, sql[i + 2]) == 'L') ||
-+           sql[i] == '/')))
-     {
-       DBUG_PRINT("qcache", ("The statement is not a SELECT; Not cached"));
-       goto err;
-@@ -1543,6 +2040,7 @@
++    if(opt_query_cache_strip_comments)
++    {
++      /* Skip all comments and non-letter symbols */
++      uint& query_position = i;
++      char* query = sql;
++      while(query_position < query_length)
++      {
++        bool check = false;
++        char current = query[query_position];
++        switch(current)
++        {
++        case '/':
++          if(((query_position + 2) < query_length) && ('*' == query[query_position+1]) && ('!' != query[query_position+2]))
++          {
++            query_position += 2; // skip "/*"
++            do
++            {
++              if('*' == query[query_position] && '/' == query[query_position+1]) // check for "*/" (without space)
++              {
++                query_position += 2; // skip "*/" (without space)
++                break;
++              }
++              else
++              {
++                ++query_position;
++              }
++            }
++            while(query_position < query_length);
++            continue; // analyze current symbol
++          }
++          break;
++        case '-':
++          if(query[query_position+1] == '-')
++          {
++            ++query_position; // skip "-"
++          }
++          else
++          {
++            break;
++          }
++        case '#':
++          do
++          {
++            ++query_position; // skip current symbol
++            if('\n' == query[query_position])  // check for '\n'
++            {
++              ++query_position; // skip '\n'
++              break;
++            }
++          }
++          while(query_position < query_length);
++          continue; // analyze current symbol
++        case '\r':
++        case '\n':
++        case '\t':
++        case ' ':
++        case '(':
++        case ')':
++          break;
++        default:
++          check = true;
++          break; // make gcc happy
++        } // switch(current)
++        if(check)
++        {
++          if(query_position + 2 < query_length)
++          {
++            // cacheable
++            break;
++          }
++          else
++          {
++            DBUG_PRINT("qcache", ("The statement is not a SELECT; Not cached"));
++            goto err;
++          }
++        } // if(check)
++        ++query_position;
++      } // while(query_position < query_length)
++    }
++    else // if(opt_query_cache_strip_comments)
++    {
++      /*
++        Skip '(' characters in queries like following:
++        (select a from t1) union (select a from t1);
++      */
++      while (sql[i]=='(')
++        i++;
+ 
+-    /*
+-      Test if the query is a SELECT
+-      (pre-space is removed in dispatch_command).
++    } // if(opt_query_cache_strip_comments)    
++      /*
++        Test if the query is a SELECT
++        (pre-space is removed in dispatch_command).
+ 
+-      First '/' looks like comment before command it is not
+-      frequently appeared in real life, consequently we can
+-      check all such queries, too.
+-    */
++        First '/' looks like comment before command it is not
++        frequently appeared in real life, consequently we can
++        check all such queries, too.
++      */
+     if ((my_toupper(system_charset_info, sql[i])     != 'S' ||
+          my_toupper(system_charset_info, sql[i + 1]) != 'E' ||
+          my_toupper(system_charset_info, sql[i + 2]) != 'L') &&
+@@ -1543,6 +1827,14 @@
      goto err_unlock;
  
    Query_cache_block *query_block;
-+  comments_processor.remove_comments();
++  if(opt_query_cache_strip_comments)
++  {
++    query_strip_comments->set(sql, query_length,
++                              QUERY_BUFFER_ADDITIONAL_LENGTH(thd->db_length));
++    sql          = query_strip_comments->query();
++    query_length = query_strip_comments->query_length();
++    *(size_t *) (sql + query_length + 1)= thd->db_length;
++  }
  
    tot_length= query_length + 1 + sizeof(size_t) + 
                thd->db_length + QUERY_CACHE_FLAGS_SIZE;
-@@ -1611,6 +2109,7 @@
+@@ -1611,6 +1903,8 @@
  	 (uchar*) &flags, QUERY_CACHE_FLAGS_SIZE);
    query_block = (Query_cache_block *)  my_hash_search(&queries, (uchar*) sql,
                                                        tot_length);
-+  comments_processor.restore_comments();
++  sql          = sql_backup;
++  query_length = query_length_backup;
    /* Quick abort on unlocked data */
    if (query_block == 0 ||
        query_block->query()->result() == 0 ||
 --- a/sql/sql_class.h
 +++ b/sql/sql_class.h
-@@ -1485,6 +1485,74 @@
- 
- extern "C" void my_message_sql(uint error, const char *str, myf MyFlags);
- 
-+
-+#ifdef HAVE_QUERY_CACHE
-+
-+
-+/*
-+  @class Query_Without_Comments
-+  This class provides way for safety (re)allocation
-+  a memory for a query without comments.
-+*/
-+class Query_Without_Comments
-+{
-+private:
-+  /*
-+    Denied copy and assigment for object of this class.
-+  */
-+  Query_Without_Comments(const Query_Without_Comments&);
-+  Query_Without_Comments& operator=(const Query_Without_Comments&);
-+
-+
-+public:
-+  /*
-+    Constructor is filling fields by zero (no allocation).
-+  */
-+  Query_Without_Comments();
-+
-+
-+  /*
-+    Destructor clean allocated memory
-+  */
-+  ~Query_Without_Comments();
-+public:
-+
-+
-+/*
-+    (Re)allocate memory for query. Query length after that is 0.
-+  */
-+  bool allocate(size_t query_length, size_t db_length);
-+
-+
-+  /*
-+    Set result query length, when query
-+    without comments is copied to buffer.
-+  */
-+  void set_length(size_t query_length);
-+
-+
-+public:
-+  /*
-+    Result query.
-+  */
-+  char*  query();
-+
-+
-+  /*
-+    Result query length
-+  */
-+  size_t length();
-+
-+
-+private:
-+  char* buffer;
-+  size_t q_length;
-+  size_t b_length;
-+};
-+
-+
-+#endif /* HAVE_QUERY_CACHE */
-+
- /**
-   @class THD
-   For each client connection we create a separate thread with THD serving as
-@@ -1542,6 +1610,7 @@
-   struct st_mysql_stmt *current_stmt;
- #endif
- #ifdef HAVE_QUERY_CACHE
-+  Query_Without_Comments query_without_comments;
-   Query_cache_tls query_cache_tls;
- #endif
-   NET	  net;				// client connection descriptor
+@@ -40,6 +40,9 @@
+ #include "thr_lock.h"             /* thr_lock_type, THR_LOCK_DATA,
+                                      THR_LOCK_INFO */
+ 
++#ifdef HAVE_QUERY_CACHE
++#include "query_strip_comments.h"
++#endif // HAVE_QUERY_CACHE
+ 
+ class Reprepare_observer;
+ class Relay_log_info;
+@@ -766,6 +769,9 @@
+     statement lifetime. FIXME: must be const
+   */
+    ulong id;
++#ifdef HAVE_QUERY_CACHE
++  QueryStripComments query_strip_comments; // see sql_cache.cc
++#endif //HAVE_QUERY_CACHE
+ 
+   /*
+     MARK_COLUMNS_NONE:  Means mark_used_colums is not set and no indicator to
 --- a/sql/sys_vars.cc
 +++ b/sql/sys_vars.cc
-@@ -1888,6 +1888,11 @@
+@@ -1895,6 +1895,11 @@
         NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
         ON_UPDATE(fix_query_cache_size));
  
@@ -733,7 +495,7 @@
         "Don't cache results that are bigger than this",
 --- /dev/null
 +++ b/mysql-test/include/percona_query_cache_with_comments.inc
-@@ -0,0 +1,117 @@
+@@ -0,0 +1,95 @@
 +--source include/percona_query_cache_with_comments_clear.inc
 +let $query=/* with comment first */select * from t1;
 +eval $query;
@@ -827,30 +589,8 @@
 +;
 +--source include/percona_query_cache_with_comments_eval.inc
 +
-+let $query=select */* a comment \*/from t1;
-+--source include/percona_query_cache_with_comments_eval.inc
-+
-+let $query=select *# a comment \\
-+from t1;
-+--source include/percona_query_cache_with_comments_eval.inc
-+
-+let $query=select *-- a comment \\
-+from t1;
-+--source include/percona_query_cache_with_comments_eval.inc
-+
-+let $query=select "\\\\"" /* not a comment */" from t1;
-+--source include/percona_query_cache_with_comments_eval.inc
-+
-+let $query=select "\\\\"" /*! not a comment */" from t1;
-+--source include/percona_query_cache_with_comments_eval.inc
-+
-+# following two queries related to bug #856404.
-+# There are different queries, but opt_query_cache_strip_comments thinks that they are equal.
 +let $query=select ' \'  ' from t1;
 +--source include/percona_query_cache_with_comments_eval.inc
-+
-+let $query=select ' \' /* comment inside quotes with internal backslash quote */' from t1;
-+--source include/percona_query_cache_with_comments_eval.inc
 --- /dev/null
 +++ b/mysql-test/include/percona_query_cache_with_comments_begin.inc
 @@ -0,0 +1,12 @@
@@ -903,7 +643,7 @@
 +
 --- /dev/null
 +++ b/mysql-test/r/percona_query_cache_with_comments.result
-@@ -0,0 +1,1058 @@
+@@ -0,0 +1,866 @@
 +set global query_cache_strip_comments=ON;
 +set GLOBAL query_cache_size=1355776;
 +drop table if exists t1;
@@ -1737,228 +1477,36 @@
 +Variable_name	Value
 +Qcache_hits	50
 +-----------------------------------------------------
-+select */* a comment \*/from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	1
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	1
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	50
-+select */* a comment \*/from t1;
-+a
-+1
-+2
-+3
-+select */* a comment \*/from t1;
-+a
-+1
-+2
-+3
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	1
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	1
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	52
-+-----------------------------------------------------
-+select *# a comment \
-+from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	1
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	1
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	52
-+select *# a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+select *# a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	1
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	1
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	54
-+-----------------------------------------------------
-+select *-- a comment \
-+from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	1
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	1
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	54
-+select *-- a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+select *-- a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	1
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	1
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	56
-+-----------------------------------------------------
-+select "\\"" /* not a comment */" from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	1
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	1
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	56
-+select "\\"" /* not a comment */" from t1;
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+select "\\"" /* not a comment */" from t1;
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	2
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	2
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	57
-+-----------------------------------------------------
-+select "\\"" /*! not a comment */" from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	2
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	2
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	57
-+select "\\"" /*! not a comment */" from t1;
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+select "\\"" /*! not a comment */" from t1;
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	3
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	3
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	58
-+-----------------------------------------------------
 +select ' \'  ' from t1
 +-----------------------------------------------------
 +show status like "Qcache_queries_in_cache";
 +Variable_name	Value
-+Qcache_queries_in_cache	3
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	3
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	58
-+select ' \'  ' from t1;
-+'  
-+ '  
-+ '  
-+ '  
-+select ' \'  ' from t1;
-+'  
-+ '  
-+ '  
-+ '  
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	4
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	4
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	59
-+-----------------------------------------------------
-+select ' \' /* comment inside quotes with internal backslash quote */' from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	4
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	4
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	59
-+select ' \' /* comment inside quotes with internal backslash quote */' from t1;
-+' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+select ' \' /* comment inside quotes with internal backslash quote */' from t1;
-+' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	5
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	5
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	60
++Qcache_queries_in_cache	1
++show status like "Qcache_inserts";
++Variable_name	Value
++Qcache_inserts	1
++show status like "Qcache_hits";
++Variable_name	Value
++Qcache_hits	50
++select ' \'  ' from t1;
++'  
++ '  
++ '  
++ '  
++select ' \'  ' from t1;
++'  
++ '  
++ '  
++ '  
++show status like "Qcache_queries_in_cache";
++Variable_name	Value
++Qcache_queries_in_cache	2
++show status like "Qcache_inserts";
++Variable_name	Value
++Qcache_inserts	2
++show status like "Qcache_hits";
++Variable_name	Value
++Qcache_hits	51
 +DROP TABLE t1;
 +SET GLOBAL query_cache_size=default;
 +set global query_cache_strip_comments=OFF;
@@ -1988,7 +1536,7 @@
 +SET GLOBAL query_cache_size= default;
 --- /dev/null
 +++ b/mysql-test/r/percona_query_cache_with_comments_disable.result
-@@ -0,0 +1,1057 @@
+@@ -0,0 +1,865 @@
 +set GLOBAL query_cache_size=1355776;
 +drop table if exists t1;
 +create table t1 (a int not null);
@@ -2821,228 +2369,36 @@
 +Variable_name	Value
 +Qcache_hits	25
 +-----------------------------------------------------
-+select */* a comment \*/from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	20
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	20
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	25
-+select */* a comment \*/from t1;
-+a
-+1
-+2
-+3
-+select */* a comment \*/from t1;
-+a
-+1
-+2
-+3
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	21
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	21
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	26
-+-----------------------------------------------------
-+select *# a comment \
-+from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	21
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	21
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	26
-+select *# a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+select *# a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	22
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	22
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	27
-+-----------------------------------------------------
-+select *-- a comment \
-+from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	22
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	22
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	27
-+select *-- a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+select *-- a comment \
-+from t1;
-+a
-+1
-+2
-+3
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	23
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	23
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	28
-+-----------------------------------------------------
-+select "\\"" /* not a comment */" from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	23
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	23
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	28
-+select "\\"" /* not a comment */" from t1;
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+select "\\"" /* not a comment */" from t1;
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+\" /* not a comment */
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	24
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	24
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	29
-+-----------------------------------------------------
-+select "\\"" /*! not a comment */" from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	24
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	24
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	29
-+select "\\"" /*! not a comment */" from t1;
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+select "\\"" /*! not a comment */" from t1;
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+\" /*! not a comment */
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	25
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	25
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	30
-+-----------------------------------------------------
 +select ' \'  ' from t1
 +-----------------------------------------------------
 +show status like "Qcache_queries_in_cache";
 +Variable_name	Value
-+Qcache_queries_in_cache	25
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	25
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	30
-+select ' \'  ' from t1;
-+'  
-+ '  
-+ '  
-+ '  
-+select ' \'  ' from t1;
-+'  
-+ '  
-+ '  
-+ '  
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	26
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	26
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	31
-+-----------------------------------------------------
-+select ' \' /* comment inside quotes with internal backslash quote */' from t1
-+-----------------------------------------------------
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	26
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	26
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	31
-+select ' \' /* comment inside quotes with internal backslash quote */' from t1;
-+' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+select ' \' /* comment inside quotes with internal backslash quote */' from t1;
-+' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+ ' /* comment inside quotes with internal backslash quote */
-+show status like "Qcache_queries_in_cache";
-+Variable_name	Value
-+Qcache_queries_in_cache	27
-+show status like "Qcache_inserts";
-+Variable_name	Value
-+Qcache_inserts	27
-+show status like "Qcache_hits";
-+Variable_name	Value
-+Qcache_hits	32
++Qcache_queries_in_cache	20
++show status like "Qcache_inserts";
++Variable_name	Value
++Qcache_inserts	20
++show status like "Qcache_hits";
++Variable_name	Value
++Qcache_hits	25
++select ' \'  ' from t1;
++'  
++ '  
++ '  
++ '  
++select ' \'  ' from t1;
++'  
++ '  
++ '  
++ '  
++show status like "Qcache_queries_in_cache";
++Variable_name	Value
++Qcache_queries_in_cache	21
++show status like "Qcache_inserts";
++Variable_name	Value
++Qcache_inserts	21
++show status like "Qcache_hits";
++Variable_name	Value
++Qcache_hits	26
 +DROP TABLE t1;
 +SET GLOBAL query_cache_size=default;
 +set global query_cache_strip_comments=OFF;
@@ -3735,7 +3091,7 @@
 +SET GLOBAL query_cache_size=0;
 --- a/mysql-test/r/mysqld--help-notwin.result
 +++ b/mysql-test/r/mysqld--help-notwin.result
-@@ -493,6 +493,10 @@
+@@ -500,6 +500,10 @@
   The minimum size for blocks allocated by the query cache
   --query-cache-size=# 
   The memory allocated to store results from old queries
@@ -3746,7 +3102,7 @@
   --query-cache-type=name 
   OFF = Don't cache or retrieve results. ON = Cache all
   results except SELECT SQL_NO_CACHE ... queries. DEMAND =
-@@ -931,6 +935,7 @@
+@@ -942,6 +946,7 @@
  query-cache-limit 1048576
  query-cache-min-res-unit 4096
  query-cache-size 0
@@ -3778,7 +3134,7 @@
 +try_lock_mutex_query
 +SET GLOBAL query_cache_size=0;
 --- /dev/null
-+++ b/mysql-test/r/percona_query_cache_with_comments_crash_2.result
++++ b/mysql-test/r/percona_bug856404.result
 @@ -0,0 +1,8 @@
 +DROP TABLE IF EXISTS table17_int;
 +DROP TABLE IF EXISTS table30_int;
@@ -3789,120 +3145,24 @@
 +DROP TABLE table17_int;
 +DROP TABLE table30_int;
 --- /dev/null
-+++ b/mysql-test/t/percona_query_cache_with_comments_crash_2-master.opt
++++ b/mysql-test/t/percona_bug856404-master.opt
 @@ -0,0 +1 @@
 +--query-cache-size=10M --query-cache-strip-comments
 --- /dev/null
-+++ b/mysql-test/t/percona_query_cache_with_comments_crash_2.test
-@@ -0,0 +1,9 @@
++++ b/mysql-test/t/percona_bug856404.test
+@@ -0,0 +1,15 @@
++########################################################################
++# Bug #856404: Crash when query_cache_strip_comments enabled
++########################################################################
++
 +--disable_warnings
 +DROP TABLE IF EXISTS table17_int;
 +DROP TABLE IF EXISTS table30_int;
 +--enable_warnings
++
 +CREATE TABLE `table17_int` (pk integer auto_increment primary key, `col_char_10_not_null_key` char(10), `col_enum_not_null_key` int);
 +CREATE TABLE `table30_int` (pk integer auto_increment primary key, `col_enum_not_null_key` int);
 +SELECT X . `pk` FROM `table17_int` AS X LEFT JOIN `table30_int` AS Y USING ( `col_enum_not_null_key` ) WHERE X . `col_char_10_not_null_key` != '   you need to translate Views labels into other languages, consider installing the <a href=\" !path\">Internationalization</a> package\'s Views translation module.' LIMIT 7  /*Generated by THREAD_ID 1*/;
++
 +DROP TABLE table17_int;
 +DROP TABLE table30_int;
---- a/sql/sql_class.cc
-+++ b/sql/sql_class.cc
-@@ -807,6 +807,99 @@
-           sql_errno == ER_TRG_NO_DEFINER);
- }
- 
-+#ifdef HAVE_QUERY_CACHE
-+
-+
-+Query_Without_Comments::Query_Without_Comments() :
-+  buffer(0),
-+  q_length(0),
-+  b_length(0)
-+{
-+}
-+
-+
-+Query_Without_Comments::~Query_Without_Comments()
-+{
-+  if(buffer)
-+  {
-+    my_free(buffer);
-+  }
-+}
-+
-+
-+bool Query_Without_Comments::allocate(size_t query_length, size_t db_length)
-+{
-+  DBUG_ENTER("Query_Without_Comments::allocate");
-+  DBUG_PRINT("info", ("old buffer: %p "
-+                      "old query: '%-.4096s' "
-+                      "old buffer length: %u "
-+                      "old query length: %u",
-+                      buffer,
-+                      buffer,
-+                      (uint) b_length,
-+                      (uint) q_length));
-+  /* save maximum query length for check in the set_length */
-+  q_length= query_length;
-+  /* according to sql_parse.cc memory allocation */
-+  size_t new_b_length= (query_length + 1) + sizeof(size_t) + db_length +
-+    QUERY_CACHE_FLAGS_SIZE;
-+  if (b_length < new_b_length)
-+  {
-+    b_length= new_b_length;
-+    if (buffer)
-+    {
-+      buffer= (char*) my_realloc(buffer, b_length, MYF(0));
-+    }
-+    else
-+    {
-+      buffer= (char *) my_malloc(b_length, MYF(0));
-+    }
-+  }
-+  buffer[0]= 0;
-+  DBUG_PRINT("info", ("buffer: %p "
-+                      "buffer length: %u "
-+                      "query maximum length: %u",
-+                      buffer,
-+                      (uint) b_length,
-+                      (uint) q_length));
-+  DBUG_RETURN(buffer);
-+}
-+
-+
-+void Query_Without_Comments::set_length(size_t query_length)
-+{
-+  DBUG_ENTER("Query_Without_Comments::set_length");
-+  DBUG_ASSERT(query_length <= q_length);
-+  buffer[query_length]= 0;
-+  DBUG_PRINT("info", ("buffer: %p "
-+                      "query: '%-.4096s' "
-+                      "buffer length: %u "
-+                      "query maximum length: %u "
-+                      "query length: %u",
-+                      buffer,
-+                      buffer,
-+                      (uint) b_length,
-+                      (uint) q_length,
-+                      (uint) query_length));
-+  q_length= query_length;
-+  DBUG_VOID_RETURN;
-+}
-+
-+
-+char* Query_Without_Comments::query()
-+{
-+  return buffer;
-+}
-+
-+
-+size_t Query_Without_Comments::length()
-+{
-+  return q_length;
-+}
-+
-+
-+#endif // HAVE_QUERY_CACHE
-+
- 
- THD::THD()
-    :Statement(&main_lex, &main_mem_root, STMT_CONVENTIONAL_EXECUTION,