Hi, While researching hash index, I found that hash_page_items could return an invalid result as follows.
postgres(1:1056)=# create table hash_test (c int); CREATE TABLE postgres(1:1056)=# insert into hash_test select generate_series(1,50) % 5; INSERT 0 50 postgres(1:1056)=# create index hash_idx on hash_test using hash (c); CREATE INDEX postgres(1:1056)=# create extension pageinspect ; CREATE EXTENSION postgres(1:1056)=# select * from hash_page_items(get_raw_page('hash_idx', 4)); itemoffset | ctid | data ------------+--------------------+------------ 1 | (0,49) | 3283889963 2 | (2139062143,32639) | 2139062143 3 | (2139062143,32639) | 2139062143 4 | (2139062143,32639) | 2139062143 5 | (2139062143,32639) | 2139062143 6 | (2139062143,32639) | 2139062143 7 | (2139062143,32639) | 2139062143 8 | (2139062143,32639) | 2139062143 9 | (2139062143,32639) | 2139062143 10 | (2139062143,32639) | 2139062143 (10 rows) This appears at PostgreSQL 10 and current HEAD. The cause of this seems that hash_page_items allocates the memory space for the page before switching memory context. AFAICS there is no similar problem in pageinspect contrib module. Attached patch fixes it. Regards, -- Masahiko Sawada NIPPON TELEGRAPH AND TELEPHONE CORPORATION NTT Open Source Software Center
fix_hash_page_items.patch
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