Fix join alias expansion in lateral TABLESAMPLE clauses
preprocess_expression skips flatten_join_alias_vars for TABLESAMPLE
clauses, on the assumption that they cannot contain Vars of the
current query level. That's not true once a LATERAL subquery
containing a sampled relation has been pulled up: the relation's
TABLESAMPLE clause then becomes a lateral reference of this level, and
if it referred to a join alias Var, that Var is left unexpanded.
extract_lateral_references then pulls the join alias Var out as a
lateral reference and fails with "no relation entry for relid N".
To fix, treat such clauses like lateral function and VALUES RTEs:
introduce EXPRKIND_TABLESAMPLE_LATERAL, used for the TABLESAMPLE
clause of a lateral relation RTE, and keep skipping the alias
expansion only for the non-lateral kind.
Back-patch to all supported branches, as this dates back to the
introduction of TABLESAMPLE.
Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Ewan Young <kdbase.hack@gmail.com>
Reviewed-by: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
Discussion: https://postgr.es/m/CAMbWs4834TwOtyyycyvja3MuOBkfpXy3dFAL0zt_vcM1KtqV-Q@mail.gmail.com
Backpatch-through: 14
Branch
------
REL_14_STABLE
Details
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https://git.postgresql.org/pg/commitdiff/df1196369080a8ec42e5820d7653039a01061ec8
Modified Files
--------------
src/backend/optimizer/plan/planner.c | 14 ++++++++++----
src/test/regress/expected/tablesample.out | 32 +++++++++++++++++++++++++++++++
src/test/regress/sql/tablesample.sql | 12 ++++++++++++
3 files changed, 54 insertions(+), 4 deletions(-)
