Bug#38002 table_cache consumes too much memory with blobs

     
Tables in the table definition cache are keeping a cache buffer for blob
fields which can consume a lot of memory.
    
This patch introduces a maximum size threshold for these buffers.

1 files changed, 22 insertions, 0 deletions

diff --git a/sql/table.cc b/sql/table.cc
index ebf3dfd748e..58cbde74822 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -1999,6 +1999,28 @@ void free_blobs(register TABLE *table)
 }
 
 
+/**
+  Reclaim temporary blob storage which is bigger than 
+  a threshold.
+ 
+  @param table A handle to the TABLE object containing blob fields
+  @param size The threshold value.
+ 
+*/
+
+void free_field_buffers_larger_than(TABLE *table, uint32 size)
+{
+  uint *ptr, *end;
+  for (ptr= table->s->blob_field, end=ptr + table->s->blob_fields ;
+       ptr != end ;
+       ptr++)
+  {
+    Field_blob *blob= (Field_blob*) table->field[*ptr];
+    if (blob->get_field_buffer_size() > size)
+        blob->free();
+  }
+}
+
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