Mixing
Speed up an activerecord query for distinct count
0
I came across this answer for speeding up a query, saying to use
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
instead of
COUNT(DISTINCT column_name)
How would one go about writing this change in activerecord (short of just writing as an sql statement)?
sql ruby-on-rails activerecord postgresql-10
edited Nov 20 '18 at 18:47
rene
33.3k1178105
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
add a comment |
0
I came across this answer for speeding up a query, saying to use
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
instead of
COUNT(DISTINCT column_name)
How would one go about writing this change in activerecord (short of just writing as an sql statement)?
sql ruby-on-rails activerecord postgresql-10
edited Nov 20 '18 at 18:47
rene
33.3k1178105
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
Well, this answer is 5 years old, optimizer get more sophisticated. You should try first, if it actually returns a different plan (you might also checkSELECT COUNT(*) FROM (SELECT column_name FROM table_name GROUP BY column_name) AS temp;, which is another rewrite). But a decent optimizer should create the same plan anyway.
– dnoeth
Nov 19 '18 at 19:44
I'd like to compare the plan for both but haven't had time. The timed results are similar though, so you may be correct - it might not matter.
– Ryan Clark
Nov 19 '18 at 19:56
add a comment |
0
0
0
I came across this answer for speeding up a query, saying to use
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
instead of
COUNT(DISTINCT column_name)
How would one go about writing this change in activerecord (short of just writing as an sql statement)?
sql ruby-on-rails activerecord postgresql-10
edited Nov 20 '18 at 18:47
rene
33.3k1178105
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
I came across this answer for speeding up a query, saying to use
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
instead of
COUNT(DISTINCT column_name)
How would one go about writing this change in activerecord (short of just writing as an sql statement)?
sql ruby-on-rails activerecord postgresql-10
sql ruby-on-rails activerecord postgresql-10
edited Nov 20 '18 at 18:47
rene
33.3k1178105
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
edited Nov 20 '18 at 18:47
rene
33.3k1178105
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
edited Nov 20 '18 at 18:47
rene
33.3k1178105
edited Nov 20 '18 at 18:47
rene
33.3k1178105
edited Nov 20 '18 at 18:47
rene
33.3k1178105
33.3k1178105
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
asked Nov 19 '18 at 19:30
Ryan ClarkRyan Clark
5551725
5551725
Well, this answer is 5 years old, optimizer get more sophisticated. You should try first, if it actually returns a different plan (you might also checkSELECT COUNT(*) FROM (SELECT column_name FROM table_name GROUP BY column_name) AS temp;, which is another rewrite). But a decent optimizer should create the same plan anyway.
– dnoeth
Nov 19 '18 at 19:44
I'd like to compare the plan for both but haven't had time. The timed results are similar though, so you may be correct - it might not matter.
– Ryan Clark
Nov 19 '18 at 19:56
add a comment |
Well, this answer is 5 years old, optimizer get more sophisticated. You should try first, if it actually returns a different plan (you might also checkSELECT COUNT(*) FROM (SELECT column_name FROM table_name GROUP BY column_name) AS temp;, which is another rewrite). But a decent optimizer should create the same plan anyway.
– dnoeth
Nov 19 '18 at 19:44
I'd like to compare the plan for both but haven't had time. The timed results are similar though, so you may be correct - it might not matter.
– Ryan Clark
Nov 19 '18 at 19:56
Well, this answer is 5 years old, optimizer get more sophisticated. You should try first, if it actually returns a different plan (you might also check
SELECT COUNT(*) FROM (SELECT column_name FROM table_name GROUP BY column_name) AS temp;, which is another rewrite). But a decent optimizer should create the same plan anyway.– dnoeth
Nov 19 '18 at 19:44
Well, this answer is 5 years old, optimizer get more sophisticated. You should try first, if it actually returns a different plan (you might also check
SELECT COUNT(*) FROM (SELECT column_name FROM table_name GROUP BY column_name) AS temp;, which is another rewrite). But a decent optimizer should create the same plan anyway.– dnoeth
Nov 19 '18 at 19:44
I'd like to compare the plan for both but haven't had time. The timed results are similar though, so you may be correct - it might not matter.
– Ryan Clark
Nov 19 '18 at 19:56
I'd like to compare the plan for both but haven't had time. The timed results are similar though, so you may be correct - it might not matter.
– Ryan Clark
Nov 19 '18 at 19:56
add a comment |
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Well, this answer is 5 years old, optimizer get more sophisticated. You should try first, if it actually returns a different plan (you might also check
SELECT COUNT(*) FROM (SELECT column_name FROM table_name GROUP BY column_name) AS temp;, which is another rewrite). But a decent optimizer should create the same plan anyway.– dnoeth
Nov 19 '18 at 19:44
I'd like to compare the plan for both but haven't had time. The timed results are similar though, so you may be correct - it might not matter.
– Ryan Clark
Nov 19 '18 at 19:56