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create table tbl ( id bigint primary key, a int );
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insert into tbl (id, a) select s, case when random() < .5 then s end from generate_series(0, 100) s; select * from tbl;
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id a
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create function coalesce_r_sfunc(state anyelement, value anyelement) returns anyelement immutable parallel safe as $$ select coalesce(value, state); $$ language sql;
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create aggregate find_last_ignore_nulls(anyelement) ( sfunc = coalesce_r_sfunc, stype = anyelement );
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select *, ( select a from tbl it where it.id <= t.id and it.a is not null order by id desc limit 1 ) lnn from tbl t;
id a lnn
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select *, find_last_ignore_nulls(a) over (order by id) from tbl;
id a find_last_ignore_nulls
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