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From:Ingo Struewing Date:September 29 2008 10:34am
Subject:bzr commit into mysql-5.1 branch (ingo.struewing:2746) Bug#37958
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#At file:///home2/mydev/bzrroot/mysql-5.1-bug37958/

 2746 Ingo Struewing	2008-09-29
      Bug#37958 - test main.plugin crash on Mac OS X when selecting from EXAMPLE engine.
      
      This patch contains fixes for two problems:
      
      1. As originally reported, the server crashed on Mac OS X when trying to access
         an EXAMPLE table after the EXAMPLE plugin was installed.
            
         It turned out that the dynamically loaded EXAMPLE plugin called the
         function hash_earch() from a Mac OS X system library, instead of
         hash_earch() from MySQL's mysys library. Makefile.am in storage/example
         does not include libmysys. So the Mac OS X linker arranged the hash_search()
         function to be linked to the system library when the shared object is
         loaded.
            
         One possible solution would be to include libmysys into the linkage of
         dynamic plugins. But then we must have a libmysys.so, which must be
         used by the server too. This could have a minimal performance impact,
         but foremost the change seems to bee too risky at the current state of
         MySQL 5.1.
            
         The selected solution is to rename MySQL's hash_search() to my_hash_search()
         like it has been done before with hash_insert() and hash_reset().
            
         Since this is the third time, we need to rename a hash_*() function,
         I did renamed all hash_*() functions to my_hash_*().
            
         To avoid changing a zillion calls to these functions, and announcing
         this to hundreds of developers, I added defines that map the old names
         to the new names.
      
         This change is in hash.h and hash.c.
      
      2. The other problem was improper implementation of the handlerton-to-plugin
         mapping. We use a fixed-size array to hold a plugin reference for each
         handlerton. On every install of a handler plugin, we allocated a new slot
         of the array. On uninstall we did not free it. After some uninstall/install
         cycles the array overflowed. We did not check for overflow.
            
         One fix is to check for overflow to stop the crashes.
            
         Another fix is to free the array slot at uninstall and search for a free slot
         at plugin install.
      
         This change is in handler.cc.
modified:
  include/hash.h
  mysys/hash.c
  sql/handler.cc

per-file messages:
  include/hash.h
    Bug#37958 - test main.plugin crash on Mac OS X when selecting from EXAMPLE engine.
    Renamed hash_*() functions to my_hash_*().
    Added defines that map old names to new names.
  mysys/hash.c
    Bug#37958 - test main.plugin crash on Mac OS X when selecting from EXAMPLE engine.
    Renamed hash_*() functions to my_hash_*().
  sql/handler.cc
    Bug#37958 - test main.plugin crash on Mac OS X when selecting from EXAMPLE engine.
    Protect against a failing ha_initialize_handlerton() in ha_finalize_handlerton().
    Free hton2plugin slot on uninstall of a handler plugin.
    Reuse freed slost of the hton2plugin array.
        Protect against array overrun.
=== modified file 'include/hash.h'
--- a/include/hash.h	2008-03-18 09:45:36 +0000
+++ b/include/hash.h	2008-09-29 10:34:07 +0000
@@ -22,6 +22,40 @@ extern "C" {
 #endif
 
 /*
+  There was a problem on MacOSX with a shared object ha_example.so.
+  It used hash_search(). During build of ha_example.so no libmysys
+  was specified. Since MacOSX had a hash_search() in the system
+  library, it built the shared object so that the dynamic linker
+  linked hash_search() to the system library, which caused a crash
+  when called. To come around this, we renamed hash_search() to
+  my_hash_search(), as we did long ago with hash_insert() and
+  hash_reset(). However, this time we made the move complete with
+  all names. To keep compatibility, we redefine the old names.
+  Since every C and C++ file, that uses HASH, needs to include
+  this file, the change is complete. Both names could be used
+  in the code, but the my_* versions are recommended now.
+*/
+#define hash_get_key    my_hash_get_key
+#define hash_free_key   my_hash_free_key
+#define hash_init       my_hash_init
+#define hash_init2      my_hash_init2
+#define _hash_init      _my_hash_init
+#define hash_free       my_hash_free
+#define hash_reset      my_hash_reset
+#define hash_element    my_hash_element
+#define hash_search     my_hash_search
+#define hash_first      my_hash_first
+#define hash_next       my_hash_next
+#define hash_insert     my_hash_insert
+#define hash_delete     my_hash_delete
+#define hash_update     my_hash_update
+#define hash_replace    my_hash_replace
+#define hash_check      my_hash_check
+#define hash_clear      my_hash_clear
+#define hash_inited     my_hash_inited
+#define hash_init_opt   my_hash_init_opt
+
+/*
   Overhead to store an element in hash
   Can be used to approximate memory consumption for a hash
  */
@@ -30,8 +64,8 @@ extern "C" {
 /* flags for hash_init */
 #define HASH_UNIQUE     1       /* hash_insert fails on duplicate key */
 
-typedef uchar *(*hash_get_key)(const uchar *,size_t*,my_bool);
-typedef void (*hash_free_key)(void *);
+typedef uchar *(*my_hash_get_key)(const uchar *,size_t*,my_bool);
+typedef void (*my_hash_free_key)(void *);
 
 typedef struct st_hash {
   size_t key_offset,key_length;		/* Length of key if const length */
@@ -39,7 +73,7 @@ typedef struct st_hash {
   ulong records;
   uint flags;
   DYNAMIC_ARRAY array;				/* Place for hash_keys */
-  hash_get_key get_key;
+  my_hash_get_key get_key;
   void (*free)(void *);
   CHARSET_INFO *charset;
 } HASH;
@@ -47,30 +81,34 @@ typedef struct st_hash {
 /* A search iterator state */
 typedef uint HASH_SEARCH_STATE;
 
-#define hash_init(A,B,C,D,E,F,G,H) _hash_init(A,0,B,C,D,E,F,G,H CALLER_INFO)
-#define hash_init2(A,B,C,D,E,F,G,H,I) _hash_init(A,B,C,D,E,F,G,H,I CALLER_INFO)
-my_bool _hash_init(HASH *hash, uint growth_size,CHARSET_INFO *charset,
-		   ulong default_array_elements, size_t key_offset,
-		   size_t key_length, hash_get_key get_key,
-		   void (*free_element)(void*), uint flags CALLER_INFO_PROTO);
-void hash_free(HASH *tree);
+#define my_hash_init(A,B,C,D,E,F,G,H) \
+          _my_hash_init(A,0,B,C,D,E,F,G,H CALLER_INFO)
+#define my_hash_init2(A,B,C,D,E,F,G,H,I) \
+          _my_hash_init(A,B,C,D,E,F,G,H,I CALLER_INFO)
+my_bool _my_hash_init(HASH *hash, uint growth_size, CHARSET_INFO *charset,
+                      ulong default_array_elements, size_t key_offset,
+                      size_t key_length, my_hash_get_key get_key,
+                      void (*free_element)(void*),
+                      uint flags CALLER_INFO_PROTO);
+void my_hash_free(HASH *tree);
 void my_hash_reset(HASH *hash);
-uchar *hash_element(HASH *hash,ulong idx);
-uchar *hash_search(const HASH *info, const uchar *key, size_t length);
-uchar *hash_first(const HASH *info, const uchar *key, size_t length,
-                HASH_SEARCH_STATE *state);
-uchar *hash_next(const HASH *info, const uchar *key, size_t length,
-                 HASH_SEARCH_STATE *state);
-my_bool my_hash_insert(HASH *info,const uchar *data);
-my_bool hash_delete(HASH *hash,uchar *record);
-my_bool hash_update(HASH *hash,uchar *record,uchar *old_key,size_t old_key_length);
-void hash_replace(HASH *hash, HASH_SEARCH_STATE *state, uchar *new_row);
-my_bool hash_check(HASH *hash);			/* Only in debug library */
-
-#define hash_clear(H) bzero((char*) (H),sizeof(*(H)))
-#define hash_inited(H) ((H)->array.buffer != 0)
-#define hash_init_opt(A,B,C,D,E,F,G,H) \
-          (!hash_inited(A) && _hash_init(A,0,B,C,D,E,F,G, H CALLER_INFO))
+uchar *my_hash_element(HASH *hash, ulong idx);
+uchar *my_hash_search(const HASH *info, const uchar *key, size_t length);
+uchar *my_hash_first(const HASH *info, const uchar *key, size_t length,
+                     HASH_SEARCH_STATE *state);
+uchar *my_hash_next(const HASH *info, const uchar *key, size_t length,
+                    HASH_SEARCH_STATE *state);
+my_bool my_hash_insert(HASH *info, const uchar *data);
+my_bool my_hash_delete(HASH *hash, uchar *record);
+my_bool my_hash_update(HASH *hash, uchar *record, uchar *old_key,
+                       size_t old_key_length);
+void my_hash_replace(HASH *hash, HASH_SEARCH_STATE *state, uchar *new_row);
+my_bool my_hash_check(HASH *hash); /* Only in debug library */
+
+#define my_hash_clear(H) bzero((char*) (H), sizeof(*(H)))
+#define my_hash_inited(H) ((H)->array.buffer != 0)
+#define my_hash_init_opt(A,B,C,D,E,F,G,H) \
+          (!my_hash_inited(A) && _my_hash_init(A,0,B,C,D,E,F,G, H CALLER_INFO))
 
 #ifdef	__cplusplus
 }

=== modified file 'mysys/hash.c'
--- a/mysys/hash.c	2008-03-18 09:45:36 +0000
+++ b/mysys/hash.c	2008-09-29 10:34:07 +0000
@@ -33,7 +33,7 @@ typedef struct st_hash_info {
   uchar *data;					/* data for current entry */
 } HASH_LINK;
 
-static uint hash_mask(uint hashnr,uint buffmax,uint maxlength);
+static uint my_hash_mask(uint hashnr, uint buffmax, uint maxlength);
 static void movelink(HASH_LINK *array,uint pos,uint next_link,uint newlink);
 static int hashcmp(const HASH *hash, HASH_LINK *pos, const uchar *key,
                    size_t length);
@@ -46,19 +46,19 @@ static uint calc_hash(const HASH *hash, 
 }
 
 my_bool
-_hash_init(HASH *hash,uint growth_size, CHARSET_INFO *charset,
-	   ulong size, size_t key_offset, size_t key_length,
-	   hash_get_key get_key,
-	   void (*free_element)(void*),uint flags CALLER_INFO_PROTO)
+_my_hash_init(HASH *hash, uint growth_size, CHARSET_INFO *charset,
+              ulong size, size_t key_offset, size_t key_length,
+              my_hash_get_key get_key,
+              void (*free_element)(void*), uint flags CALLER_INFO_PROTO)
 {
-  DBUG_ENTER("hash_init");
+  DBUG_ENTER("my_hash_init");
   DBUG_PRINT("enter",("hash: 0x%lx  size: %u", (long) hash, (uint) size));
 
   hash->records=0;
   if (my_init_dynamic_array_ci(&hash->array, sizeof(HASH_LINK), size,
                                growth_size))
   {
-    hash->free=0;				/* Allow call to hash_free */
+    hash->free=0;				/* Allow call to my_hash_free */
     DBUG_RETURN(1);
   }
   hash->key_offset=key_offset;
@@ -76,14 +76,14 @@ _hash_init(HASH *hash,uint growth_size, 
   Call hash->free on all elements in hash.
 
   SYNOPSIS
-    hash_free_elements()
+    my_hash_free_elements()
     hash   hash table
 
   NOTES:
     Sets records to 0
 */
 
-static inline void hash_free_elements(HASH *hash)
+static inline void my_hash_free_elements(HASH *hash)
 {
   if (hash->free)
   {
@@ -100,18 +100,18 @@ static inline void hash_free_elements(HA
   Free memory used by hash.
 
   SYNOPSIS
-    hash_free()
+    my_hash_free()
     hash   the hash to delete elements of
 
-  NOTES: Hash can't be reused without calling hash_init again.
+  NOTES: Hash can't be reused without calling my_hash_init again.
 */
 
-void hash_free(HASH *hash)
+void my_hash_free(HASH *hash)
 {
-  DBUG_ENTER("hash_free");
+  DBUG_ENTER("my_hash_free");
   DBUG_PRINT("enter",("hash: 0x%lx", (long) hash));
 
-  hash_free_elements(hash);
+  my_hash_free_elements(hash);
   hash->free= 0;
   delete_dynamic(&hash->array);
   DBUG_VOID_RETURN;
@@ -131,7 +131,7 @@ void my_hash_reset(HASH *hash)
   DBUG_ENTER("my_hash_reset");
   DBUG_PRINT("enter",("hash: 0x%lxd", (long) hash));
 
-  hash_free_elements(hash);
+  my_hash_free_elements(hash);
   reset_dynamic(&hash->array);
   /* Set row pointers so that the hash can be reused at once */
   hash->blength= 1;
@@ -146,8 +146,8 @@ void my_hash_reset(HASH *hash)
 */
 
 static inline char*
-hash_key(const HASH *hash, const uchar *record, size_t *length,
-         my_bool first)
+my_hash_key(const HASH *hash, const uchar *record, size_t *length,
+            my_bool first)
 {
   if (hash->get_key)
     return (char*) (*hash->get_key)(record,length,first);
@@ -157,18 +157,18 @@ hash_key(const HASH *hash, const uchar *
 
 	/* Calculate pos according to keys */
 
-static uint hash_mask(uint hashnr,uint buffmax,uint maxlength)
+static uint my_hash_mask(uint hashnr, uint buffmax, uint maxlength)
 {
   if ((hashnr & (buffmax-1)) < maxlength) return (hashnr & (buffmax-1));
   return (hashnr & ((buffmax >> 1) -1));
 }
 
-static uint hash_rec_mask(const HASH *hash, HASH_LINK *pos,
-                          uint buffmax, uint maxlength)
+static uint my_hash_rec_mask(const HASH *hash, HASH_LINK *pos,
+                             uint buffmax, uint maxlength)
 {
   size_t length;
-  uchar *key= (uchar*) hash_key(hash,pos->data,&length,0);
-  return hash_mask(calc_hash(hash,key,length),buffmax,maxlength);
+  uchar *key= (uchar*) my_hash_key(hash, pos->data, &length, 0);
+  return my_hash_mask(calc_hash(hash, key, length), buffmax, maxlength);
 }
 
 
@@ -181,15 +181,15 @@ inline
 unsigned int rec_hashnr(HASH *hash,const uchar *record)
 {
   size_t length;
-  uchar *key= (uchar*) hash_key(hash,record,&length,0);
+  uchar *key= (uchar*) my_hash_key(hash, record, &length, 0);
   return calc_hash(hash,key,length);
 }
 
 
-uchar* hash_search(const HASH *hash, const uchar *key, size_t length)
+uchar* my_hash_search(const HASH *hash, const uchar *key, size_t length)
 {
   HASH_SEARCH_STATE state;
-  return hash_first(hash, key, length, &state);
+  return my_hash_first(hash, key, length, &state);
 }
 
 /*
@@ -199,18 +199,18 @@ uchar* hash_search(const HASH *hash, con
    Assigns the number of the found record to HASH_SEARCH_STATE state
 */
 
-uchar* hash_first(const HASH *hash, const uchar *key, size_t length,
-                HASH_SEARCH_STATE *current_record)
+uchar* my_hash_first(const HASH *hash, const uchar *key, size_t length,
+                     HASH_SEARCH_STATE *current_record)
 {
   HASH_LINK *pos;
   uint flag,idx;
-  DBUG_ENTER("hash_first");
+  DBUG_ENTER("my_hash_first");
 
   flag=1;
   if (hash->records)
   {
-    idx=hash_mask(calc_hash(hash,key,length ? length : hash->key_length),
-		    hash->blength,hash->records);
+    idx= my_hash_mask(calc_hash(hash, key, length ? length : hash->key_length),
+                      hash->blength, hash->records);
     do
     {
       pos= dynamic_element(&hash->array,idx,HASH_LINK*);
@@ -223,7 +223,7 @@ uchar* hash_first(const HASH *hash, cons
       if (flag)
       {
 	flag=0;					/* Reset flag */
-	if (hash_rec_mask(hash,pos,hash->blength,hash->records) != idx)
+	if (my_hash_rec_mask(hash, pos, hash->blength, hash->records) != idx)
 	  break;				/* Wrong link */
       }
     }
@@ -234,10 +234,10 @@ uchar* hash_first(const HASH *hash, cons
 }
 
 	/* Get next record with identical key */
-	/* Can only be called if previous calls was hash_search */
+	/* Can only be called if previous calls was my_hash_search */
 
-uchar* hash_next(const HASH *hash, const uchar *key, size_t length,
-               HASH_SEARCH_STATE *current_record)
+uchar* my_hash_next(const HASH *hash, const uchar *key, size_t length,
+                    HASH_SEARCH_STATE *current_record)
 {
   HASH_LINK *pos;
   uint idx;
@@ -297,7 +297,7 @@ static int hashcmp(const HASH *hash, HAS
                    size_t length)
 {
   size_t rec_keylength;
-  uchar *rec_key= (uchar*) hash_key(hash,pos->data,&rec_keylength,1);
+  uchar *rec_key= (uchar*) my_hash_key(hash, pos->data, &rec_keylength, 1);
   return ((length && length != rec_keylength) ||
 	  my_strnncoll(hash->charset, (uchar*) rec_key, rec_keylength,
 		       (uchar*) key, rec_keylength));
@@ -306,7 +306,7 @@ static int hashcmp(const HASH *hash, HAS
 
 	/* Write a hash-key to the hash-index */
 
-my_bool my_hash_insert(HASH *info,const uchar *record)
+my_bool my_hash_insert(HASH *info, const uchar *record)
 {
   int flag;
   size_t idx;
@@ -321,8 +321,8 @@ my_bool my_hash_insert(HASH *info,const 
 
   if (HASH_UNIQUE & info->flags)
   {
-    uchar *key= (uchar*) hash_key(info, record, &idx, 1);
-    if (hash_search(info, key, idx))
+    uchar *key= (uchar*) my_hash_key(info, record, &idx, 1);
+    if (my_hash_search(info, key, idx))
       return(TRUE);				/* Duplicate entry */
   }
 
@@ -341,7 +341,7 @@ my_bool my_hash_insert(HASH *info,const 
       pos=data+idx;
       hash_nr=rec_hashnr(info,pos->data);
       if (flag == 0)				/* First loop; Check if ok */
-	if (hash_mask(hash_nr,info->blength,info->records) != first_index)
+	if (my_hash_mask(hash_nr, info->blength, info->records) != first_index)
 	  break;
       if (!(hash_nr & halfbuff))
       {						/* Key will not move */
@@ -413,7 +413,7 @@ my_bool my_hash_insert(HASH *info,const 
   }
   /* Check if we are at the empty position */
 
-  idx=hash_mask(rec_hashnr(info,record),info->blength,info->records+1);
+  idx= my_hash_mask(rec_hashnr(info, record), info->blength, info->records + 1);
   pos=data+idx;
   if (pos == empty)
   {
@@ -424,7 +424,7 @@ my_bool my_hash_insert(HASH *info,const 
   {
     /* Check if more records in same hash-nr family */
     empty[0]=pos[0];
-    gpos=data+hash_rec_mask(info,pos,info->blength,info->records+1);
+    gpos= data + my_hash_rec_mask(info, pos, info->blength, info->records + 1);
     if (pos == gpos)
     {
       pos->data=(uchar*) record;
@@ -449,18 +449,18 @@ my_bool my_hash_insert(HASH *info,const 
 ** if there is a free-function it's called for record if found
 ******************************************************************************/
 
-my_bool hash_delete(HASH *hash,uchar *record)
+my_bool my_hash_delete(HASH *hash, uchar *record)
 {
   uint blength,pos2,pos_hashnr,lastpos_hashnr,idx,empty_index;
   HASH_LINK *data,*lastpos,*gpos,*pos,*pos3,*empty;
-  DBUG_ENTER("hash_delete");
+  DBUG_ENTER("my_hash_delete");
   if (!hash->records)
     DBUG_RETURN(1);
 
   blength=hash->blength;
   data=dynamic_element(&hash->array,0,HASH_LINK*);
   /* Search after record with key */
-  pos=data+ hash_mask(rec_hashnr(hash,record),blength,hash->records);
+  pos= data + my_hash_mask(rec_hashnr(hash, record), blength, hash->records);
   gpos = 0;
 
   while (pos->data != record)
@@ -491,7 +491,7 @@ my_bool hash_delete(HASH *hash,uchar *re
   /* Move the last key (lastpos) */
   lastpos_hashnr=rec_hashnr(hash,lastpos->data);
   /* pos is where lastpos should be */
-  pos=data+hash_mask(lastpos_hashnr,hash->blength,hash->records);
+  pos= data + my_hash_mask(lastpos_hashnr, hash->blength, hash->records);
   if (pos == empty)			/* Move to empty position. */
   {
     empty[0]=lastpos[0];
@@ -499,7 +499,7 @@ my_bool hash_delete(HASH *hash,uchar *re
   }
   pos_hashnr=rec_hashnr(hash,pos->data);
   /* pos3 is where the pos should be */
-  pos3= data+hash_mask(pos_hashnr,hash->blength,hash->records);
+  pos3= data + my_hash_mask(pos_hashnr, hash->blength, hash->records);
   if (pos != pos3)
   {					/* pos is on wrong posit */
     empty[0]=pos[0];			/* Save it here */
@@ -507,8 +507,8 @@ my_bool hash_delete(HASH *hash,uchar *re
     movelink(data,(uint) (pos-data),(uint) (pos3-data),empty_index);
     goto exit;
   }
-  pos2= hash_mask(lastpos_hashnr,blength,hash->records+1);
-  if (pos2 == hash_mask(pos_hashnr,blength,hash->records+1))
+  pos2= my_hash_mask(lastpos_hashnr, blength, hash->records + 1);
+  if (pos2 == my_hash_mask(pos_hashnr, blength, hash->records + 1))
   {					/* Identical key-positions */
     if (pos2 != hash->records)
     {
@@ -536,26 +536,26 @@ exit:
 	  This is much more efficent than using a delete & insert.
 	  */
 
-my_bool hash_update(HASH *hash, uchar *record, uchar *old_key,
-                    size_t old_key_length)
+my_bool my_hash_update(HASH *hash, uchar *record, uchar *old_key,
+                       size_t old_key_length)
 {
   uint new_index,new_pos_index,blength,records,empty;
   size_t idx;
   HASH_LINK org_link,*data,*previous,*pos;
-  DBUG_ENTER("hash_update");
+  DBUG_ENTER("my_hash_update");
   
   if (HASH_UNIQUE & hash->flags)
   {
     HASH_SEARCH_STATE state;
-    uchar *found, *new_key= (uchar*) hash_key(hash, record, &idx, 1);
-    if ((found= hash_first(hash, new_key, idx, &state)))
+    uchar *found, *new_key= (uchar*) my_hash_key(hash, record, &idx, 1);
+    if ((found= my_hash_first(hash, new_key, idx, &state)))
     {
       do 
       {
         if (found != record)
           DBUG_RETURN(1);		/* Duplicate entry */
       } 
-      while ((found= hash_next(hash, new_key, idx, &state)));
+      while ((found= my_hash_next(hash, new_key, idx, &state)));
     }
   }
 
@@ -564,11 +564,11 @@ my_bool hash_update(HASH *hash, uchar *r
 
   /* Search after record with key */
 
-  idx=hash_mask(calc_hash(hash, old_key,(old_key_length ?
-					      old_key_length :
-					      hash->key_length)),
-		  blength,records);
-  new_index=hash_mask(rec_hashnr(hash,record),blength,records);
+  idx= my_hash_mask(calc_hash(hash, old_key, (old_key_length ?
+                                              old_key_length :
+                                              hash->key_length)),
+                    blength, records);
+  new_index= my_hash_mask(rec_hashnr(hash, record), blength, records);
   if (idx == new_index)
     DBUG_RETURN(0);			/* Nothing to do (No record check) */
   previous=0;
@@ -618,7 +618,7 @@ my_bool hash_update(HASH *hash, uchar *r
     DBUG_RETURN(0);
   }
   pos=data+new_index;
-  new_pos_index=hash_rec_mask(hash,pos,blength,records);
+  new_pos_index= my_hash_rec_mask(hash, pos, blength, records);
   if (new_index != new_pos_index)
   {					/* Other record in wrong position */
     data[empty] = *pos;
@@ -636,7 +636,7 @@ my_bool hash_update(HASH *hash, uchar *r
 }
 
 
-uchar *hash_element(HASH *hash,ulong idx)
+uchar *my_hash_element(HASH *hash, ulong idx)
 {
   if (idx < hash->records)
     return dynamic_element(&hash->array,idx,HASH_LINK*)->data;
@@ -649,7 +649,8 @@ uchar *hash_element(HASH *hash,ulong idx
   isn't changed
 */
 
-void hash_replace(HASH *hash, HASH_SEARCH_STATE *current_record, uchar *new_row)
+void my_hash_replace(HASH *hash, HASH_SEARCH_STATE *current_record,
+                     uchar *new_row)
 {
   if (*current_record != NO_RECORD)            /* Safety */
     dynamic_element(&hash->array, *current_record, HASH_LINK*)->data= new_row;
@@ -658,7 +659,7 @@ void hash_replace(HASH *hash, HASH_SEARC
 
 #ifndef DBUG_OFF
 
-my_bool hash_check(HASH *hash)
+my_bool my_hash_check(HASH *hash)
 {
   int error;
   uint i,rec_link,found,max_links,seek,links,idx;
@@ -671,7 +672,7 @@ my_bool hash_check(HASH *hash)
 
   for (i=found=max_links=seek=0 ; i < records ; i++)
   {
-    if (hash_rec_mask(hash,data+i,blength,records) == i)
+    if (my_hash_rec_mask(hash, data + i, blength, records) == i)
     {
       found++; seek++; links=1;
       for (idx=data[i].next ;
@@ -687,11 +688,12 @@ my_bool hash_check(HASH *hash)
 	}
 	hash_info=data+idx;
 	seek+= ++links;
-	if ((rec_link=hash_rec_mask(hash,hash_info,blength,records)) != i)
+	if ((rec_link= my_hash_rec_mask(hash, hash_info,
+                                        blength, records)) != i)
 	{
-	  DBUG_PRINT("error",
-		     ("Record in wrong link at %d: Start %d  Record: 0x%lx  Record-link %d",
-                      idx, i, (long) hash_info->data, rec_link));
+          DBUG_PRINT("error", ("Record in wrong link at %d: Start %d  "
+                               "Record: 0x%lx  Record-link %d",
+                               idx, i, (long) hash_info->data, rec_link));
 	  error=1;
 	}
 	else

=== modified file 'sql/handler.cc'
--- a/sql/handler.cc	2008-09-05 15:21:59 +0000
+++ b/sql/handler.cc	2008-09-29 10:34:07 +0000
@@ -373,6 +373,10 @@ int ha_finalize_handlerton(st_plugin_int
   handlerton *hton= (handlerton *)plugin->data;
   DBUG_ENTER("ha_finalize_handlerton");
 
+  /* hton can be NULL here, if ha_initialize_handlerton() failed. */
+  if (!hton)
+    goto end;
+
   switch (hton->state)
   {
   case SHOW_OPTION_NO:
@@ -401,8 +405,16 @@ int ha_finalize_handlerton(st_plugin_int
     }
   }
 
+  /*
+    In case a plugin is uninstalled and re-installed later, it should
+    reuse an array slot. Otherwise the number of uninstall/install
+    cycles would be limited.
+  */
+  hton2plugin[hton->slot]= NULL;
+
   my_free((uchar*)hton, MYF(0));
 
+ end:
   DBUG_RETURN(0);
 }
 
@@ -437,6 +449,7 @@ int ha_initialize_handlerton(st_plugin_i
   case SHOW_OPTION_YES:
     {
       uint tmp;
+      ulong fslot;
       /* now check the db_type for conflict */
       if (hton->db_type <= DB_TYPE_UNKNOWN ||
           hton->db_type >= DB_TYPE_DEFAULT ||
@@ -461,7 +474,31 @@ int ha_initialize_handlerton(st_plugin_i
       tmp= hton->savepoint_offset;
       hton->savepoint_offset= savepoint_alloc_size;
       savepoint_alloc_size+= tmp;
-      hton->slot= total_ha++;
+
+      /*
+        In case a plugin is uninstalled and re-installed later, it should
+        reuse an array slot. Otherwise the number of uninstall/install
+        cycles would be limited. So look for a free slot.
+      */
+      DBUG_PRINT("plugin", ("total_ha: %lu", total_ha));
+      for (fslot= 0; fslot < total_ha; fslot++)
+      {
+        if (!hton2plugin[fslot])
+          break;
+      }
+      if (fslot < total_ha)
+        hton->slot= fslot;
+      else
+      {
+        if (total_ha >= MAX_HA)
+        {
+          sql_print_error("Too many plugins loaded. Limit is %lu. "
+                          "Failed on '%s'", (ulong) MAX_HA, plugin->name.str);
+          goto err;
+        }
+        hton->slot= total_ha++;
+      }
+
       hton2plugin[hton->slot]=plugin;
       if (hton->prepare)
         total_ha_2pc++;

Thread
bzr commit into mysql-5.1 branch (ingo.struewing:2746) Bug#37958Ingo Struewing29 Sep