Code cleanup:

- Move [some] engine-agnostic tests from t/selectivity.test to t/selectivity_no_engine.test
- Move Histogram::point_selectivity to sql_statistics.cc

1 files changed, 1 insertions, 111 deletions

diff --git a/sql/sql_statistics.h b/sql/sql_statistics.h
index d0db0a3bf33..331e3559203 100644
--- a/sql/sql_statistics.h
+++ b/sql/sql_statistics.h
@@ -241,120 +241,10 @@ public:
     return sel;
   } 
   
-  
   /*
     Estimate selectivity of "col=const" using a histogram
-    
-    @param pos      Position of the "const" between column's min_value and 
-                    max_value.  This is a number in [0..1] range.
-    @param avg_sel  Average selectivity of condition "col=const" in this table.
-                    It is calcuated as (#non_null_values / #distinct_values).
-    
-    @return
-       Expected condition selectivity (a number between 0 and 1)
-
-    @notes 
-       [re_zero_length_buckets] If a bucket with zero value-length is in the
-       middle of the histogram, we will not have min==max. Example: suppose, 
-       pos_value=0x12, and the histogram is:
-
-             #n  #n+1 #n+2                 
-        ... 0x10 0x12 0x12 0x14 ...
-                        |
-                        +------------- bucket with zero value-length
-      
-        Here, we will get min=#n+1, max=#n+2, and use the multi-bucket formula.
-       
-        The problem happens at the histogram ends. if pos_value=0, and the
-        histogram is:
-
-        0x00 0x10 ...
-
-        then min=0, max=0. This means pos_value is contained within bucket #0,
-        but on the other hand, histogram data says that the bucket has only one
-        value.
   */
-
-  double point_selectivity(double pos, double avg_sel)
-  {
-    double sel;
-    /* Find the bucket that contains the value 'pos'. */
-    uint min= find_bucket(pos, TRUE);
-    uint pos_value= (uint) (pos * prec_factor());
-
-    /* Find how many buckets this value occupies */
-    uint max= min;
-    while (max + 1 < get_width() && get_value(max + 1) == pos_value)
-      max++;
-    
-    /*
-      A special case: we're looking at a single bucket, and that bucket has
-      zero value-length. Use the multi-bucket formula (attempt to use
-      single-bucket formula will cause divison by zero).
-
-      For more details see [re_zero_length_buckets] above.
-    */
-    if (max == min && get_value(max) == ((max==0)? 0 : get_value(max-1)))
-      max++;
-
-    if (max > min)
-    {
-      /*
-        The value occupies multiple buckets. Use start_bucket ... end_bucket as
-        selectivity.
-      */
-      double bucket_sel= 1.0/(get_width() + 1);  
-      sel= bucket_sel * (max - min + 1);
-    }
-    else
-    {
-      /* 
-        The value 'pos' fits within one single histogram bucket.
-
-        Histogram buckets have the same numbers of rows, but they cover
-        different ranges of values.
-
-        We assume that values are uniformly distributed across the [0..1] value
-        range.
-      */
-
-      /* 
-        If all buckets covered value ranges of the same size, the width of
-        value range would be:
-      */
-      double avg_bucket_width= 1.0 / (get_width() + 1);
-      
-      /*
-        Let's see what is the width of value range that our bucket is covering.
-          (min==max currently. they are kept in the formula just in case we 
-           will want to extend it to handle multi-bucket case)
-      */
-      double inv_prec_factor= (double) 1.0 / prec_factor(); 
-      double current_bucket_width= 
-          (max + 1 == get_width() ?  1.0 : (get_value(max) * inv_prec_factor)) -
-          (min == 0 ?  0.0 : (get_value(min-1) * inv_prec_factor));
-
-      DBUG_ASSERT(current_bucket_width); /* We shouldn't get a one zero-width bucket */
-
-      /*
-        So:
-        - each bucket has the same #rows 
-        - values are unformly distributed across the [min_value,max_value] domain.
-
-        If a bucket has value range that's N times bigger then average, than
-        each value will have to have N times fewer rows than average.
-      */
-      sel= avg_sel * avg_bucket_width / current_bucket_width;
-
-      /*
-        (Q: if we just follow this proportion we may end up in a situation
-        where number of different values we expect to find in this bucket
-        exceeds the number of rows that this histogram has in a bucket. Are 
-        we ok with this or we would want to have certain caps?)
-      */
-    }
-    return sel;
-  }
+  double point_selectivity(double pos, double avg_sel);
 };