Consider the following: anything = WorkoutExercise.find_all_by_exercise_id(params[:id]) if (anything.empty?) do_something else do_something_else end Is the array returned in ''anything'' an intelligent proxy to the database? If the result set was a terabyte of data am I in trouble? If so, what should I do? Thanks, Cris -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit https://groups.google.com/groups/opt_out.
On Friday, February 8, 2013 4:28:58 AM UTC+8, Ruby-Forum.com User wrote:> > Consider the following: > > anything = WorkoutExercise.find_all_by_exercise_id(params[:id]) > if (anything.empty?) > do_something > else > do_something_else > end > > > > Is the array returned in ''anything'' an intelligent proxy to the > database? >Any time you call .all, .first or find (including find_all_by_...) you''re actually executing the query and unless you use find_each the entirety of the results will be materialised. The result is an actual array (or an active record object in the case of .first), not a proxy to anything.> If the result set was a terabyte of data am I in trouble? If so, what > should I do? > > I''d do something likeif WorkoutExercise.where(:exercise_id =>(params[:id]).exists? ... end assuming you don''t actually need the result set. If you do need to do stuff with the result set, use find_each to process the query in batches. Fred Thanks,> > Cris > > -- > Posted via http://www.ruby-forum.com/. >-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To view this discussion on the web visit https://groups.google.com/d/msg/rubyonrails-talk/-/Mt69CCja54wJ. For more options, visit https://groups.google.com/groups/opt_out.
Fred,
Thank you.
We tested what you gave =us with ActiveRecord logging to STDOUT and with
this code:
puts ''hi''
e = WorkoutExercise.where(:exercise_id =>(params[:id]))
puts "after"
e.exists?
puts "last one"
We saw this:
hi
after
Primary Key (15.0ms) SELECT cc.column_name FROM all_constraints c,
all_cons_columns cc WHERE c.owner = ''BROWNBAG'' AND
c.table_name ''WORKOUT_EXERCISES'' AND c.constraint_type =
''P'' AND cc.owner = c.owner
AND cc.constraint_name = c.constraint_name
workout_exercises Columns (16.0ms) SELECT column_name AS name,
data_type AS sql_type, data_default, nullable, virtual_column,
hidden_column, DECODE(data_type, ''NUMBER'', data_precision,
''FLOAT'',
data_precision, ''VARCHAR2'', DECODE(char_used,
''C'', char_length,
data_length), ''RAW'', DECODE(char_used, ''C'',
char_length, data_length),
''CHAR'', DECODE(char_used, ''C'', char_length,
data_length), NULL) AS
limit, DECODE(data_type, ''NUMBER'', data_scale, NULL) AS scale
FROM
all_tab_cols WHERE owner = ''BROWNBAG'' AND table_name
''WORKOUT_EXERCISES'' AND hidden_column = ''NO''
ORDER BY column_id
WorkoutExercise Exists (157.0ms) SELECT 1 AS one FROM
"WORKOUT_EXERCISES" WHERE
"WORKOUT_EXERCISES"."EXERCISE_ID" = 980190962
AND ROWNUM <= 1
last one
So sure enough the query waits until exists? is called!
Thanks!
Cris
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