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81e2f35d4b
This patch marks the function cagg_watermark as PARALLEL RESTRICTED. It partially reverts the change of c0f2ed18095f21ac737f96fe93e4035dbfeeaf2c. The reason is as follows: for transaction isolation levels < REPEATABLE READ it can not be ensured that parallel worker reads the same watermark (e.g., using read committed isolation level: worker A reads the watermark, the CAGG is refreshed and the watermark changes, worker B reads the newer watermark). The different views on the CAGG can cause unexpected results and crashes (e.g., the chunk exclusion excludes different chunks in worker A and in worker B). In addition, a correct snapshot is used when the watermark is read from the CAGG and a TAP test is added, which detects inconsistent watermark reads. Co-authored-by: Fabrízio de Royes Mello <fabriziomello@gmail.com> Co-authored-by: Zoltan Haindrich <zoltan@timescale.com>