EXPLAIN select o_year, sum(case when nation = 'ETHIOPIA' then volume else 0 end) / sum(volume) as mkt_share from ( select extract(year from o_orderdate) as o_year, l_extendedprice * (1 - l_discount) as volume, n2.n_name as nation from part, supplier, lineitem, orders, customer, nation n1, nation n2, region where p_partkey = l_partkey and s_suppkey = l_suppkey and l_orderkey = o_orderkey and o_custkey = c_custkey and c_nationkey = n1.n_nationkey and n1.n_regionkey = r_regionkey and r_name = 'AFRICA' and s_nationkey = n2.n_nationkey and o_orderdate between date '1995-01-01' and date '1996-12-31' and p_type = 'LARGE ANODIZED NICKEL' ) as all_nations group by o_year order by o_year;
                                      plan                                       
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                                      sort                                      
                                                                                
                                       map                                      
                                                                                
                                     groupby                                    
                                                                                
                                       map                                      
                                                                                
                                      join                                      
                                      hash                                      
                                                                                
 tablescan                                join                                  
 nation                                   indexnl                               
                                                                                
                                      join                             tablescan
                                      hash                             supplier 
                                                                                
                  join                         join                             
                  hash                         indexnl                          
                                                                                
           tablescan tablescan            join               tablescan          
           region    nation               indexnl            customer           
                                                                                
                                      join         tablescan                    
                                      hash         orders                       
                                                                                
                               tablescan tablescan                              
                               part      lineitem                               
(28 rows)