Fixed table crash bug when updating row > 16M (Bug #2159)

myisam/mi_dynrec.c:
  Fixed table crash bug when updating row > 16M

myisam/mi_dynrec.c

@@ -14,7 +14,15 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
-	/* Functions to handle space-packed-records and blobs */
+/*
+  Functions to handle space-packed-records and blobs
+ 
+  A row may be stored in one or more linked blocks.
+  The block size is between MI_MIN_BLOCK_LENGTH and MI_MAX_BLOCK_LENGTH.
+  Each block is aligned on MI_DYN_ALIGN_SIZE.
+  The reson for the max block size is to not have too many different types
+  of blocks.  For the differnet block types, look at _mi_get_block_info()
+*/
 
 #include "myisamdef.h"
 #include <assert.h>
@@ -264,37 +272,62 @@ static bool unlink_deleted_block(MI_INFO *info, MI_BLOCK_INFO *block_info)
   DBUG_RETURN(0);
 }
 
-	/* Delete datarecord from database */
-	/* info->rec_cache.seek_not_done is updated in cmp_record */
 
-static int delete_dynamic_record(MI_INFO *info, my_off_t filepos,
-				 uint second_read)
+/*
+  Add a backward link to delete block
+
+  SYNOPSIS
+    update_backward_delete_link()
+    info		MyISAM handler
+    delete_block	Position to delete block to update.
+			If this is 'HA_OFFSET_ERROR', nothing will be done
+    filepos		Position to block that 'delete_block' should point to
+
+  RETURN
+    0  ok
+    1  error.  In this case my_error is set.
+*/
+
+static int update_backward_delete_link(MI_INFO *info, my_off_t delete_block,
+				       my_off_t filepos)
 {
-  uint length,b_type;
-  MI_BLOCK_INFO block_info,del_block;
-  int error=0;
-  my_bool remove_next_block;
-  DBUG_ENTER("delete_dynamic_record");
+  MI_BLOCK_INFO block_info;
+  DBUG_ENTER("update_backward_delete_link");
 
-  /* First add a link from the last block to the new one */
-  if (info->s->state.dellink != HA_OFFSET_ERROR)
+  if (delete_block != HA_OFFSET_ERROR)
   {
     block_info.second_read=0;
-    if (_mi_get_block_info(&block_info,info->dfile,info->s->state.dellink)
+    if (_mi_get_block_info(&block_info,info->dfile,delete_block)
 	& BLOCK_DELETED)
     {
       char buff[8];
       mi_sizestore(buff,filepos);
-      if (my_pwrite(info->dfile,buff,8,info->s->state.dellink+12,
-		    MYF(MY_NABP)))
-	error=1;				/* Error on write */
+      if (my_pwrite(info->dfile,buff, 8, delete_block+12, MYF(MY_NABP)))
+	DBUG_RETURN(1);				/* Error on write */
     }
     else
     {
-      error=1;					/* Wrong delete link */
       my_errno=HA_ERR_WRONG_IN_RECORD;
+      DBUG_RETURN(1);				/* Wrong delete link */
     }
   }
+  return 0;
+}
+
+	/* Delete datarecord from database */
+	/* info->rec_cache.seek_not_done is updated in cmp_record */
+
+static int delete_dynamic_record(MI_INFO *info, my_off_t filepos,
+				 uint second_read)
+{
+  uint length,b_type;
+  MI_BLOCK_INFO block_info,del_block;
+  int error;
+  my_bool remove_next_block;
+  DBUG_ENTER("delete_dynamic_record");
+
+  /* First add a link from the last block to the new one */
+  error= update_backward_delete_link(info, info->s->state.dellink, filepos);
 
   block_info.second_read=second_read;
   do
@@ -518,21 +551,11 @@ int _mi_write_part_record(MI_INFO *info,
   *reclength-=(length-head_length);
   *flag=6;
 
-  if (del_length && next_delete_block != HA_OFFSET_ERROR)
+  if (del_length)
   {
     /* link the next delete block to this */
-    MI_BLOCK_INFO del_block;
-    del_block.second_read=0;
-    if (!(_mi_get_block_info(&del_block,info->dfile,next_delete_block)
-	  & BLOCK_DELETED))
-    {
-      my_errno=HA_ERR_WRONG_IN_RECORD;
-      goto err;
-    }
-    mi_sizestore(del_block.header+12,info->s->state.dellink);
-    if (my_pwrite(info->dfile,(char*) del_block.header+12,8,
-		  next_delete_block+12,
-		  MYF(MY_NABP)))
+    if (update_backward_delete_link(info, next_delete_block,
+				    info->s->state.dellink))
       goto err;
   }
 
@@ -574,6 +597,8 @@ static int update_dynamic_record(MI_INFO *info, my_off_t filepos, byte *record,
       {
 	uint tmp=MY_ALIGN(reclength - length + 3 +
 			  test(reclength >= 65520L),MI_DYN_ALIGN_SIZE);
+	/* Don't create a block bigger than MI_MAX_BLOCK_LENGTH */
+	tmp= min(length+tmp, MI_MAX_BLOCK_LENGTH)-length;
 	/* Check if we can extend this block */
 	if (block_info.filepos + block_info.block_len ==
 	    info->state->data_file_length &&
@@ -588,9 +613,15 @@ static int update_dynamic_record(MI_INFO *info, my_off_t filepos, byte *record,
 	  info->update|= HA_STATE_WRITE_AT_END | HA_STATE_EXTEND_BLOCK;
 	  length+=tmp;
 	}
-	else
+	else if (length < MI_MAX_BLOCK_LENGTH - MI_MIN_BLOCK_LENGTH)
 	{
-	  /* Check if next block is a deleted block */
+	  /*
+	    Check if next block is a deleted block
+	    Above we have MI_MIN_BLOCK_LENGTH to avoid the problem where
+	    the next block is so small it can't be splited which could
+	    casue problems
+	  */
+
 	  MI_BLOCK_INFO del_block;
 	  del_block.second_read=0;
 	  if (_mi_get_block_info(&del_block,info->dfile,
@@ -601,7 +632,35 @@ static int update_dynamic_record(MI_INFO *info, my_off_t filepos, byte *record,
 	    DBUG_PRINT("info",("Extending current block"));
 	    if (unlink_deleted_block(info,&del_block))
 	      goto err;
-	    length+=del_block.block_len;
+	    if ((length+=del_block.block_len) > MI_MAX_BLOCK_LENGTH)
+	    {
+	      /*
+		New block was too big, link overflow part back to
+		delete list
+	      */
+	      my_off_t next_pos;
+	      ulong rest_length= length-MI_MAX_BLOCK_LENGTH;
+	      set_if_bigger(rest_length, MI_MIN_BLOCK_LENGTH);
+	      next_pos= del_block.filepos+ del_block.block_len - rest_length;
+
+	      if (update_backward_delete_link(info, info->s->state.dellink,
+					      next_pos))
+		DBUG_RETURN(1);
+
+	      /* create delete link for data that didn't fit into the page */
+	      del_block.header[0]=0;
+	      mi_int3store(del_block.header+1, rest_length);
+	      mi_sizestore(del_block.header+4,info->s->state.dellink);
+	      bfill(del_block.header+12,8,255);
+	      if (my_pwrite(info->dfile,(byte*) del_block.header,20, next_pos,
+			    MYF(MY_NABP)))
+		DBUG_RETURN(1);
+	      info->s->state.dellink= next_pos;
+	      info->s->state.split++;
+	      info->state->del++;
+	      info->state->empty+= rest_length;
+	      length-= rest_length;
+	    }
 	  }
 	}
       }
@@ -615,7 +674,10 @@ static int update_dynamic_record(MI_INFO *info, my_off_t filepos, byte *record,
 			      &record,&reclength,&flag))
       goto err;
     if ((filepos=block_info.next_filepos) == HA_OFFSET_ERROR)
+    {
+      /* Start writing data on deleted blocks */
       filepos=info->s->state.dellink;
+    }
   }
 
   if (block_info.next_filepos != HA_OFFSET_ERROR)

mysql-test/r/myisam-blob.result

+drop table if exists t1;
+CREATE TABLE t1 (data LONGBLOB) ENGINE=myisam;
+INSERT INTO t1 (data) VALUES (NULL);
+UPDATE t1 set data=repeat('a',18*1024*1024);
+select length(data) from t1;
+length(data)
+18874368
+delete from t1 where left(data,1)='a';
+check table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+truncate table t1;
+INSERT INTO t1 (data) VALUES (repeat('a',1*1024*1024));
+INSERT INTO t1 (data) VALUES (repeat('b',16*1024*1024-1024));
+delete from t1 where left(data,1)='b';
+check table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+UPDATE t1 set data=repeat('c',17*1024*1024);
+check table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+delete from t1 where left(data,1)='c';
+check table t1;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+drop table t1;

mysql-test/t/myisam-blob-master.opt

+--max-allowed-packet=24M --skip-innodb --key-buffer-size=1M

mysql-test/t/myisam-blob.test

+#
+# Test bugs in the MyISAM code with blobs
+#
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+
+# Bug #2159 (Problem with update of blob to > 16M)
+
+CREATE TABLE t1 (data LONGBLOB) ENGINE=myisam;
+INSERT INTO t1 (data) VALUES (NULL);
+UPDATE t1 set data=repeat('a',18*1024*1024);
+select length(data) from t1;
+delete from t1 where left(data,1)='a';
+check table t1;
+truncate table t1;
+INSERT INTO t1 (data) VALUES (repeat('a',1*1024*1024));
+INSERT INTO t1 (data) VALUES (repeat('b',16*1024*1024-1024));
+delete from t1 where left(data,1)='b';
+check table t1;
+
+# now we have two blocks in the table, first is a 1M record and second is
+# a 16M delete block.
+
+UPDATE t1 set data=repeat('c',17*1024*1024);
+check table t1;
+delete from t1 where left(data,1)='c';
+check table t1;
+drop table t1;