Create 20240407_02.md

Author: digoal

202404/20240407_02.md

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+## PostgreSQL 17 preview - Implement `ALTER TABLE ... MERGE|SPLIT PARTITION` ... command  
+                                                                                                              
+### 作者                                                                                                              
+digoal                                                                                                              
+                                                                                                              
+### 日期                                                                                                              
+2024-04-07                                                                                                    
+                                                                                                              
+### 标签                                                                                                              
+PostgreSQL , PolarDB , DuckDB , MERGE , SPLIT , partition   
+                                                                                                              
+----                                                                                                              
+                                                                                                              
+## 背景      
+PostgreSQL 17 preview - Implement `ALTER TABLE ... MERGE|SPLIT PARTITION` ... command  
+  
+https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=1adf16b8fba45f77056d91573cd7138ed9da4ebf  
+  
+https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=87c21bb9412c8ba2727dec5ebcd74d44c2232d11  
+  
+https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/test/regress/expected/partition_merge.out;h=2ba0ec47d97807cd55eb198f53798ca0f5bc1553;hb=1adf16b8fba45f77056d91573cd7138ed9da4ebf  
+  
+https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/test/regress/expected/partition_split.out;h=0a40f20554d74721bf1b06af36b4bba5dda8b47f;hb=87c21bb9412c8ba2727dec5ebcd74d44c2232d11  
+    
+```  
+ 130 ALTER TABLE sales_range SPLIT PARTITION sales_feb_mar_apr2022 INTO  
+ 131   (PARTITION sales_feb2022 FOR VALUES FROM ('2022-02-01') TO ('2022-03-01'),  
+ 132    PARTITION sales_mar2022 FOR VALUES FROM ('2022-03-01') TO ('2022-04-01'),  
+ 133    PARTITION sales_apr2022 FOR VALUES FROM ('2022-04-01') TO ('2022-05-01'));  
+  
+ 427 ALTER TABLE salesmans MERGE PARTITIONS (salesmans10_20, salesmans20_30, salesmans30_40) INTO salesmans10_40;   
+```  
+  
+```  
+Implement ALTER TABLE ... SPLIT PARTITION ... command  
+author	Alexander Korotkov <[email protected]>	  
+Sat, 6 Apr 2024 21:58:09 +0000 (00:58 +0300)  
+committer	Alexander Korotkov <[email protected]>	  
+Sat, 6 Apr 2024 22:18:44 +0000 (01:18 +0300)  
+commit	87c21bb9412c8ba2727dec5ebcd74d44c2232d11  
+tree	3ce4f8e030b40814f251997793066a6bac115f1f	tree  
+parent	1adf16b8fba45f77056d91573cd7138ed9da4ebf	commit | diff  
+Implement ALTER TABLE ... SPLIT PARTITION ... command  
+  
+This new DDL command splits a single partition into several parititions.  
+Just like ALTER TABLE ... MERGE PARTITIONS ... command, new patitions are  
+created using createPartitionTable() function with parent partition as the  
+template.  
+  
+This commit comprises quite naive implementation which works in single process  
+and holds the ACCESS EXCLUSIVE LOCK on the parent table during all the  
+operations including the tuple routing.  This is why this new DDL command  
+can't be recommended for large partitioned tables under a high load.  However,  
+this implementation come in handy in certain cases even as is.  
+Also, it could be used as a foundation for future implementations with lesser  
+locking and possibly parallel.  
+  
+Discussion: https://postgr.es/m/c73a1746-0cd0-6bdd-6b23-3ae0b7c0c582%40postgrespro.ru  
+Author: Dmitry Koval  
+Reviewed-by: Matthias van de Meent, Laurenz Albe, Zhihong Yu, Justin Pryzby  
+Reviewed-by: Alvaro Herrera, Robert Haas, Stephane Tachoires  
+```  
+