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https://issues.apache.org/jira/browse/PIG-3919?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Philip (flip) Kromer updated PIG-3919:
--------------------------------------
Description:
Pig should allow values calculated in the main body of a FOREACH to be accessed
by and inner nested FOREACH.
{code}
top_queries = LOAD './test/data/pigunit/top_queries_input_data.txt' AS
(site:chararray, hits:int);
-- yahoo 10
-- twitter 7
-- ...
top_queries_g = GROUP top_queries BY site;
-- BREAKS: Invalid field projection. Projected field [top_queries] does not
exist in schema: site:chararray,hits:int. - org.apache.pig.tools.grunt.Grunt
cant_use_values_in_inner_foreach = FOREACH top_queries_g {
n_sites = COUNT_STAR(top_queries);
hits_x = FOREACH top_queries GENERATE hits / n_sites;
GENERATE group AS site, n_sites, hits_x;
};
DUMP cant_use_values_in_inner_foreach;
-- This works, because n_sites behaves same regardless of scope
can_use_const_val = FOREACH top_queries_g {
n_sites = 3;
hits_x = FOREACH top_queries GENERATE hits / n_sites;
GENERATE group AS site, n_sites, hits_x;
};
DUMP can_use_const_val;
{code}
Pig handles the schema for the inner foreach in a very confusing way.
It should not allow statements in the main foreach body that aren't in the
main-body scope:
{code}
works_but_is_confusing = FOREACH top_queries_g {
namelen_g = SIZE(group);
namelen_s = SIZE(site); -- this should not work
-- but it does, because namelen_s gains right scope when evaluated
hits_x = FOREACH top_queries GENERATE namelen_s * hits;
-- instead, this should work, only evaluating namelen_g once
-- hits_x = FOREACH top_queries GENERATE namelen_g * hits;
-- if I used 'namelen_s' in this line, it would break.
GENERATE group AS site, namelen_g, hits_x;
};
DUMP works_but_is_confusing;
{code}
Here, the inner foreach precedes the declaration of 'site' in the main body:
{code}
-- declaring main-body site _after_ the inner foreach doesn't interfere
alias_means_two_things = FOREACH top_queries_g {
hits_x = FOREACH top_queries GENERATE SIZE(site)*hits; -- works
site = CONCAT(group, group);
namelen_s = SIZE(site);
GENERATE site, namelen_s, hits_x;
};
DUMP alias_means_two_things;
{code}
Simply switching the order of the lines causes an error -- the main body
declaration of site hides the inner-bag alias. Also, the error shows up on the
line in the main-body, which is very confusing.
{code}
-- BREAKS
main_body_hides_alias = FOREACH top_queries_g {
site = CONCAT(group, group); -- Projected field [group] does not exist
in schema: site:chararray,hits:int
namelen_s = SIZE(site);
hits_x = FOREACH top_queries GENERATE SIZE(site)*hits;
GENERATE site, namelen_s, hits_x;
};
DUMP main_body_hides_alias;
{code}
was:
Pig should allow values calculated in the main body of a FOREACH to be accessed
by and inner nested FOREACH.
{code}
top_queries = LOAD './test/data/pigunit/top_queries_input_data.txt' AS
(site:chararray, hits:int);
-- yahoo 10
-- twitter 7
-- ...
top_queries_g = GROUP top_queries BY site;
-- BREAKS: Invalid field projection. Projected field [top_queries] does not
exist in schema: site:chararray,hits:int. - org.apache.pig.tools.grunt.Grunt
cant_use_values_in_inner_foreach = FOREACH top_queries_g {
n_sites = COUNT_STAR(top_queries);
hits_x = FOREACH top_queries GENERATE hits / n_sites;
GENERATE group AS site, n_sites, hits_x;
};
DUMP cant_use_values_in_inner_foreach;
{code}
-- This works, because n_sites behaves same regardless of scope
can_use_const_val = FOREACH top_queries_g {
n_sites = 3;
hits_x = FOREACH top_queries GENERATE hits / n_sites;
GENERATE group AS site, n_sites, hits_x;
};
DUMP can_use_const_val;
{code}
Pig handles the schema for the inner foreach in a very confusing way.
It should not allow statements in the main foreach body that aren't in the
main-body scope:
{code}
works_but_is_confusing = FOREACH top_queries_g {
namelen_g = SIZE(group);
namelen_s = SIZE(site); -- this should not work
-- but it does, because namelen_s gains right scope when evaluated
hits_x = FOREACH top_queries GENERATE namelen_s * hits;
-- instead, this should work, only evaluating namelen_g once
-- hits_x = FOREACH top_queries GENERATE namelen_g * hits;
-- if I used 'namelen_s' in this line, it would break.
GENERATE group AS site, namelen_g, hits_x;
};
DUMP works_but_is_confusing;
{code}
Here, the inner foreach precedes the declaration of 'site' in the main body:
{code}
-- declaring main-body site _after_ the inner foreach doesn't interfere
alias_means_two_things = FOREACH top_queries_g {
hits_x = FOREACH top_queries GENERATE SIZE(site)*hits; -- works
site = CONCAT(group, group);
namelen_s = SIZE(site);
GENERATE site, namelen_s, hits_x;
};
DUMP alias_means_two_things;
{code}
Simply switching the order of the lines causes an error -- the main body
declaration of site hides the inner-bag alias. Also, the error shows up on the
line in the main-body, which is very confusing.
{code}
-- BREAKS
main_body_hides_alias = FOREACH top_queries_g {
site = CONCAT(group, group); -- Projected field [group] does not exist
in schema: site:chararray,hits:int
namelen_s = SIZE(site);
hits_x = FOREACH top_queries GENERATE SIZE(site)*hits;
GENERATE site, namelen_s, hits_x;
};
DUMP main_body_hides_alias;
{code}
> Inner FOREACH of nested FOREACH should have access to main-body aliases
> -----------------------------------------------------------------------
>
> Key: PIG-3919
> URL: https://issues.apache.org/jira/browse/PIG-3919
> Project: Pig
> Issue Type: Bug
> Affects Versions: 0.12.0, 0.13.0
> Reporter: Philip (flip) Kromer
> Labels: alias, foreach, innerbag, nested, schema
>
> Pig should allow values calculated in the main body of a FOREACH to be
> accessed by and inner nested FOREACH.
> {code}
> top_queries = LOAD './test/data/pigunit/top_queries_input_data.txt' AS
> (site:chararray, hits:int);
> -- yahoo 10
> -- twitter 7
> -- ...
> top_queries_g = GROUP top_queries BY site;
> -- BREAKS: Invalid field projection. Projected field [top_queries] does not
> exist in schema: site:chararray,hits:int. - org.apache.pig.tools.grunt.Grunt
> cant_use_values_in_inner_foreach = FOREACH top_queries_g {
> n_sites = COUNT_STAR(top_queries);
> hits_x = FOREACH top_queries GENERATE hits / n_sites;
> GENERATE group AS site, n_sites, hits_x;
> };
> DUMP cant_use_values_in_inner_foreach;
> -- This works, because n_sites behaves same regardless of scope
> can_use_const_val = FOREACH top_queries_g {
> n_sites = 3;
> hits_x = FOREACH top_queries GENERATE hits / n_sites;
> GENERATE group AS site, n_sites, hits_x;
> };
> DUMP can_use_const_val;
> {code}
> Pig handles the schema for the inner foreach in a very confusing way.
> It should not allow statements in the main foreach body that aren't in the
> main-body scope:
> {code}
> works_but_is_confusing = FOREACH top_queries_g {
> namelen_g = SIZE(group);
> namelen_s = SIZE(site); -- this should not work
>
> -- but it does, because namelen_s gains right scope when evaluated
> hits_x = FOREACH top_queries GENERATE namelen_s * hits;
> -- instead, this should work, only evaluating namelen_g once
> -- hits_x = FOREACH top_queries GENERATE namelen_g * hits;
> -- if I used 'namelen_s' in this line, it would break.
> GENERATE group AS site, namelen_g, hits_x;
> };
> DUMP works_but_is_confusing;
> {code}
> Here, the inner foreach precedes the declaration of 'site' in the main body:
> {code}
> -- declaring main-body site _after_ the inner foreach doesn't interfere
> alias_means_two_things = FOREACH top_queries_g {
> hits_x = FOREACH top_queries GENERATE SIZE(site)*hits; -- works
> site = CONCAT(group, group);
> namelen_s = SIZE(site);
> GENERATE site, namelen_s, hits_x;
> };
> DUMP alias_means_two_things;
> {code}
> Simply switching the order of the lines causes an error -- the main body
> declaration of site hides the inner-bag alias. Also, the error shows up on
> the line in the main-body, which is very confusing.
> {code}
> -- BREAKS
> main_body_hides_alias = FOREACH top_queries_g {
> site = CONCAT(group, group); -- Projected field [group] does not
> exist in schema: site:chararray,hits:int
> namelen_s = SIZE(site);
> hits_x = FOREACH top_queries GENERATE SIZE(site)*hits;
> GENERATE site, namelen_s, hits_x;
> };
> DUMP main_body_hides_alias;
> {code}
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