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05c8482f7f
Parallel SELECT can't be utilized for INSERT in the following cases: - INSERT statement uses the ON CONFLICT DO UPDATE clause - Target table has a parallel-unsafe: trigger, index expression or predicate, column default expression or check constraint - Target table has a parallel-unsafe domain constraint on any column - Target table is a partitioned table with a parallel-unsafe partition key expression or support function The planner is updated to perform additional parallel-safety checks for the cases listed above, for determining whether it is safe to run INSERT in parallel-mode with an underlying parallel SELECT. The planner will consider using parallel SELECT for "INSERT INTO ... SELECT ...", provided nothing unsafe is found from the additional parallel-safety checks, or from the existing parallel-safety checks for SELECT. While checking parallel-safety, we need to check it for all the partitions on the table which can be costly especially when we decide not to use a parallel plan. So, in a separate patch, we will introduce a GUC and or a reloption to enable/disable parallelism for Insert statements. Prior to entering parallel-mode for the execution of INSERT with parallel SELECT, a TransactionId is acquired and assigned to the current transaction state. This is necessary to prevent the INSERT from attempting to assign the TransactionId whilst in parallel-mode, which is not allowed. This approach has a disadvantage in that if the underlying SELECT does not return any rows, then the TransactionId is not used, however that shouldn't happen in practice in many cases. Author: Greg Nancarrow, Amit Langote, Amit Kapila Reviewed-by: Amit Langote, Hou Zhijie, Takayuki Tsunakawa, Antonin Houska, Bharath Rupireddy, Dilip Kumar, Vignesh C, Zhihong Yu, Amit Kapila Tested-by: Tang, Haiying Discussion: https://postgr.es/m/CAJcOf-cXnB5cnMKqWEp2E2z7Mvcd04iLVmV=qpFJrR3AcrTS3g@mail.gmail.com Discussion: https://postgr.es/m/CAJcOf-fAdj=nDKMsRhQzndm-O13NY4dL6xGcEvdX5Xvbbi0V7g@mail.gmail.com |
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| .. | ||
| appendinfo.h | ||
| clauses.h | ||
| cost.h | ||
| geqo.h | ||
| geqo_copy.h | ||
| geqo_gene.h | ||
| geqo_misc.h | ||
| geqo_mutation.h | ||
| geqo_pool.h | ||
| geqo_random.h | ||
| geqo_recombination.h | ||
| geqo_selection.h | ||
| inherit.h | ||
| joininfo.h | ||
| optimizer.h | ||
| orclauses.h | ||
| paramassign.h | ||
| pathnode.h | ||
| paths.h | ||
| placeholder.h | ||
| plancat.h | ||
| planmain.h | ||
| planner.h | ||
| prep.h | ||
| restrictinfo.h | ||
| subselect.h | ||
| tlist.h | ||