Data update

Task/Text-processing-2/DuckDB/text-processing-2-1.duckdb

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+create or replace table t as
+from read_csv_auto('readings.txt', header=false);

Task/Text-processing-2/DuckDB/text-processing-2-2.duckdb

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+alter table t rename column column00 to date;

Task/Text-processing-2/DuckDB/text-processing-2-3.duckdb

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+.mode list
+.headers off
+.once dynamic.tmp
+select 'alter table t rename column ''column' || format('{:02d}', 2 * n) || ''' to ''flag' || format('{:02d}'';', n) from range(1,25) t(n);
+.read dynamic.tmp
+.mode duckdb
+.headers on

Task/Text-processing-2/DuckDB/text-processing-2-4.duckdb

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+# The values in a struct as JSON values
+create or replace function struct_values(s) as (
+  with j as (select s::JSON as j)
+  SELECT list_transform( json_keys(j), k -> j[k]) from j
+);
+
+# Number of nulls in an entire table:
+select sum(length(list_filter(struct_values(t), x -> x = 'null'))) as "|null|"
+from (select t from t);

Task/Text-processing-2/DuckDB/text-processing-2-5.duckdb

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+# j is a JSON object ; return a list of the keys for which the value is less than 1
+create or replace function report(j) as (
+  list_filter(json_keys(j), k ->  (j -> k) < 1 )
+);
+
+select count(*) from
+from (select report(struct_pack(*COLUMNS('flag'))::JSON) as flags
+      from t
+      where flags = []);

Task/Text-processing-2/DuckDB/text-processing-2-6.duckdb

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+with allflags as (
+  select array_agg(flags) as flags
+  from (select report(struct_pack(*COLUMNS('flag'))::JSON) as flags from t)
+  )
+  select list_reduce( flags, (acc,x) -> list_intersect(acc,x) ) as "never worked"
+  from allflags;