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error compressing wide table

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Consider a compressed hypertable has many columns (like more than 600 columns).
In call to compress_chunk(), the compressed tuple size exceeds, 8K which causes
error as "row is too big: size 10856, maximum size 8160."

This patch estimates the tuple size of compressed hypertable and reports a
warning when compression is enabled on hypertable. Thus user gets aware of
this warning before calling compress_chunk().

Fixes #4398
This commit is contained in:
Bharathy 2022-09-17 07:39:04 +05:30
parent ffd9dfb7eb
commit d00a55772c
4 changed files with 58 additions and 2 deletions
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1
CHANGELOG.md
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@ -22,6 +22,7 @@ argument or resolve the type ambiguity by casting to the intended type.
* #4673 Fix now() constification for VIEWs
* #4681 Fix compression_chunk_size primary key
* #4685 Improve chunk exclusion for space dimensions
* #4696 Report warning when enabling compression on hypertable
**Thanks**
* @maxtwardowski for reporting problems with chunk exclusion and space dimensions

23
src/hypertable.c
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@ -2549,8 +2549,29 @@ ts_hypertable_create_compressed(Oid table_relid, int32 hypertable_id)
NameData schema_name, table_name, associated_schema_name;
ChunkSizingInfo *chunk_sizing_info;
Relation rel;
rel = table_open(table_relid, AccessExclusiveLock);
int32 row_size = MAXALIGN(SizeofHeapTupleHeader);
/* estimate tuple width of compressed hypertable */
for (int i = 1; i <= RelationGetNumberOfAttributes(rel); i++)
{
bool is_varlena = false;
Oid outfunc;
Form_pg_attribute att = TupleDescAttr(rel->rd_att, i - 1);
getTypeOutputInfo(att->atttypid, &outfunc, &is_varlena);
if (is_varlena)
row_size += 18;
else
row_size += att->attlen;
}
if (row_size > MaxHeapTupleSize)
{
ereport(WARNING,
(errmsg("compressed row size might exceed maximum row size"),
errdetail("Estimated row size of compressed hypertable is %u. This exceeds the "
"maximum size of %zu and can cause compression of chunks to fail.",
row_size,
MaxHeapTupleSize)));
}
/*
* Check that the user has permissions to make this table to a compressed
* hypertable

21
tsl/test/expected/compression_errors.out
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File diff suppressed because one or more lines are too long

15
tsl/test/sql/compression_errors.sql
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@ -347,4 +347,17 @@ SELECT COMPRESS_CHUNK(X) FROM SHOW_CHUNKS('test') X;
--below query should pass after chunks are compressed
SELECT 1 FROM test GROUP BY enum_col;
EXPLAIN SELECT DISTINCT 1 FROM test;
EXPLAIN SELECT DISTINCT 1 FROM test;
--github issue 4398
SELECT format('CREATE TABLE data_table AS SELECT now() AS tm, %s', array_to_string(array_agg(format('125 AS c%s',a)), ', ')) FROM generate_series(1,550)a \gexec
CREATE TABLE ts_table (LIKE data_table);
SELECT * FROM create_hypertable('ts_table', 'tm');
--should report a warning
\set VERBOSITY terse
ALTER TABLE ts_table SET(timescaledb.compress, timescaledb.compress_segmentby = 'c1',
timescaledb.compress_orderby = 'tm');
INSERT INTO ts_table SELECT * FROM data_table;
--cleanup tables
DROP TABLE data_table cascade;
DROP TABLE ts_table cascade;