Added partition pruning checks (WL#2987)

3 files changed, 107 insertions, 2 deletions

diff --git a/sql/ha_ndbcluster.cc b/sql/ha_ndbcluster.cc
index 22a3ca0e302..e3eed8dfc7c 100644
--- a/sql/ha_ndbcluster.cc
+++ b/sql/ha_ndbcluster.cc
@@ -2200,6 +2200,7 @@ int ha_ndbcluster::full_table_scan(byte *buf)
   int res;
   NdbScanOperation *op;
   NdbTransaction *trans= m_active_trans;
+  part_id_range part_spec;
 
   DBUG_ENTER("full_table_scan");  
   DBUG_PRINT("enter", ("Starting new scan on %s", m_tabname));
@@ -2211,6 +2212,35 @@ int ha_ndbcluster::full_table_scan(byte *buf)
       op->readTuples(lm, 0, parallelism))
     ERR_RETURN(trans->getNdbError());
   m_active_cursor= op;
+
+  if (m_use_partition_function)
+  {
+    part_spec.start_part= 0;
+    part_spec.end_part= get_tot_partitions(m_part_info) - 1;
+    prune_partition_set(table, &part_spec);
+    DBUG_PRINT("info", ("part_spec.start_part = %u, part_spec.end_part = %u",
+                        part_spec.start_part, part_spec.end_part));
+    /*
+      If partition pruning has found no partition in set
+      we can return HA_ERR_END_OF_FILE
+      If partition pruning has found exactly one partition in set
+      we can optimize scan to run towards that partition only.
+    */
+    if (part_spec.start_part > part_spec.end_part)
+    {
+      DBUG_RETURN(HA_ERR_END_OF_FILE);
+    }
+    else if (part_spec.start_part == part_spec.end_part)
+    {
+      /*
+        Only one partition is required to scan, if sorted is required we
+        don't need it any more since output from one ordered partitioned
+        index is always sorted.
+      */
+      m_active_cursor->setPartitionId(part_spec.start_part);
+    }
+  }
+
   if (generate_scan_filter(m_cond_stack, op))
     DBUG_RETURN(ndb_err(trans));
   if ((res= define_read_attrs(buf, op)))
@@ -3020,6 +3050,14 @@ int ha_ndbcluster::read_range_first_to_buf(const key_range *start_key,
   if (m_use_partition_function)
   {
     get_partition_set(table, buf, active_index, start_key, &part_spec);
+    DBUG_PRINT("info", ("part_spec.start_part = %u, part_spec.end_part = %u",
+                        part_spec.start_part, part_spec.end_part));
+    /*
+      If partition pruning has found no partition in set
+      we can return HA_ERR_END_OF_FILE
+      If partition pruning has found exactly one partition in set
+      we can optimize scan to run towards that partition only.
+    */
     if (part_spec.start_part > part_spec.end_part)
     {
       DBUG_RETURN(HA_ERR_END_OF_FILE);
@@ -3034,6 +3072,7 @@ int ha_ndbcluster::read_range_first_to_buf(const key_range *start_key,
       sorted= FALSE;
     }
   }
+
   m_write_op= FALSE;
   switch (type){
   case PRIMARY_KEY_ORDERED_INDEX:
@@ -7009,6 +7048,12 @@ ha_ndbcluster::read_multi_range_first(KEY_MULTI_RANGE **found_range_p,
       get_partition_set(table, curr, active_index,
                         &multi_range_curr->start_key,
                         &part_spec);
+      DBUG_PRINT("info", ("part_spec.start_part = %u, part_spec.end_part = %u",
+                          part_spec.start_part, part_spec.end_part));
+      /*
+        If partition pruning has found no partition in set
+        we can skip this scan
+      */
       if (part_spec.start_part > part_spec.end_part)
       {
         /*
diff --git a/sql/handler.h b/sql/handler.h
index 92fa581c19c..6c85ea823b0 100644
--- a/sql/handler.h
+++ b/sql/handler.h
@@ -1128,6 +1128,7 @@ char *generate_partition_syntax(partition_info *part_info,
                                 uint *buf_length, bool use_sql_alloc,
                                 bool write_all);
 bool partition_key_modified(TABLE *table, List<Item> &fields);
+void prune_partition_set(const TABLE *table, part_id_range *part_spec);
 void get_partition_set(const TABLE *table, byte *buf, const uint index,
                        const key_range *key_spec,
                        part_id_range *part_spec);
diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index 290d512198f..f058e22d693 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -3605,7 +3605,55 @@ void get_full_part_id_from_key(const TABLE *table, byte *buf,
     part_spec->start_part++;
   DBUG_VOID_RETURN;
 }
-    
+
+/*
+  Prune the set of partitions to use in query 
+
+  SYNOPSIS
+    prune_partition_set()
+    table         The table object
+    out:part_spec Contains start part, end part 
+
+  DESCRIPTION
+    This function is called to prune the range of partitions to scan by
+    checking the used_partitions bitmap.
+    If start_part > end_part at return it means no partition needs to be
+    scanned. If start_part == end_part it always means a single partition
+    needs to be scanned.
+
+  RETURN VALUE
+    part_spec
+*/
+void prune_partition_set(const TABLE *table, part_id_range *part_spec)
+{
+  int last_partition= -1;
+  uint i;
+  partition_info *part_info= table->part_info;
+
+  DBUG_ENTER("prune_partition_set");
+  for (i= part_spec->start_part; i <= part_spec->end_part; i++)
+  {
+    if (bitmap_is_set(&(part_info->used_partitions), i))
+    {
+      DBUG_PRINT("info", ("Partition %d is set", i));
+      if (last_partition == -1)
+        /* First partition found in set and pruned bitmap */
+        part_spec->start_part= i;
+      last_partition= i;
+    }
+    else
+    {
+      if (last_partition == -1)
+        /* No partition found in pruned bitmap yet */
+        part_spec->start_part= i + 1;
+    }
+  }
+  if (last_partition != -1)
+    part_spec->end_part= last_partition;
+
+  DBUG_VOID_RETURN;
+}
+
 /*
   Get the set of partitions to use in query.
 
@@ -3669,6 +3717,10 @@ void get_partition_set(const TABLE *table, byte *buf, const uint index,
           is needed.
         */
         get_full_part_id_from_key(table,buf,key_info,key_spec,part_spec);
+        /*
+          Check if range can be adjusted by looking in used_partitions
+        */
+        prune_partition_set(table, part_spec);
         DBUG_VOID_RETURN;
       }
       else if (is_sub_partitioned(part_info))
@@ -3711,6 +3763,10 @@ void get_partition_set(const TABLE *table, byte *buf, const uint index,
           */
           get_full_part_id_from_key(table,buf,key_info,key_spec,part_spec);
           clear_indicator_in_key_fields(key_info);
+          /*
+            Check if range can be adjusted by looking in used_partitions
+          */
+          prune_partition_set(table, part_spec);
           DBUG_VOID_RETURN; 
         }
         else if (is_sub_partitioned(part_info))
@@ -3770,10 +3826,13 @@ void get_partition_set(const TABLE *table, byte *buf, const uint index,
   }
   if (found_part_field)
     clear_indicator_in_key_fields(key_info);
+  /*
+    Check if range can be adjusted by looking in used_partitions
+  */
+  prune_partition_set(table, part_spec);
   DBUG_VOID_RETURN;
 }
 
-
 /*
    If the table is partitioned we will read the partition info into the
    .frm file here.