我有一个查询，其中包含以下执行计划：
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| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads | OMem | 1Mem | Used-Mem |
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| 0 | SELECT STATEMENT | | 1 | | 21741 |00:00:11.38 | 150K| 1088 | | | |
| 1 | SORT AGGREGATE | | 46072 | 1 | 46072 |00:00:02.92 | 138K| 241 | | | |
| 2 | FIRST ROW | | 46072 | 1 | 3761 |00:00:02.83 | 138K| 241 | | | |
|* 3 | INDEX RANGE SCAN (MIN/MAX) | VERP_VIG_VEHICLE_STAGES_N2 | 46072 | 1 | 3761 |00:00:02.79 | 138K| 241 | | | |
|* 4 | HASH JOIN RIGHT OUTER | | 1 | 37010 | 21741 |00:00:11.38 | 150K| 1088 | 3272K| 1218K| 3302K (0)|
| 5 | VIEW | | 1 | 7402 | 23548 |00:00:11.17 | 147K| 1088 | | | |
| 6 | WINDOW SORT | | 1 | 7402 | 23548 |00:00:10.82 | 79621 | 1088 | 4801K| 915K| 4267K (0)|
|* 7 | HASH JOIN RIGHT OUTER | | 1 | 7402 | 23548 |00:00:07.84 | 8837 | 847 | 1599K| 1599K| 996K (0)|
| 8 | TABLE ACCESS FULL | VERP_OTM_PS_CONTROL_TABLE | 1 | 5 | 5 |00:00:00.01 | 39 | 0 | | | |
|* 9 | FILTER | | 1 | | 23548 |00:00:07.80 | 8798 | 847 | | | |
|* 10 | HASH JOIN RIGHT OUTER | | 1 | 7402 | 71904 |00:00:07.76 | 8798 | 847 | 1421K| 1421K| 1756K (0)|
| 11 | VIEW | | 1 | 4534 | 4554 |00:00:00.01 | 27 | 0 | | | |
|* 12 | HASH JOIN | | 1 | 4534 | 4554 |00:00:00.01 | 27 | 0 | 1888K| 1888K| 1596K (0)|
| 13 | INDEX FULL SCAN | VERP_VPS_SUPPLY_VVP_N1 | 1 | 27 | 27 |00:00:00.01 | 1 | 0 | | | |
| 14 | INDEX FULL SCAN | VERP_VPS_SUPPLY_VVVP_N1 | 1 | 4534 | 4554 |00:00:00.01 | 26 | 0 | | | |
|* 15 | HASH JOIN | | 1 | 37010 | 71904 |00:00:07.67 | 8771 | 847 | 1245K| 1245K| 1722K (0)|
| 16 | SORT UNIQUE | | 1 | 37010 | 1586 |00:00:00.05 | 3279 | 0 | 124K| 124K| 110K (0)|
| 17 | TABLE ACCESS FULL | VERP_OTM_STAGED_VONS | 1 | 37010 | 21741 |00:00:00.02 | 3279 | 0 | | | |
| 18 | TABLE ACCESS BY INDEX ROWID BATCHED| VERP_VIG_VEHICLES | 1 | 246K| 36104 |00:00:07.53 | 5492 | 847 | | | |
|* 19 | INDEX RANGE SCAN | VERP_VIG_VEHICLES_N22 | 1 | 246K| 36104 |00:00:07.38 | 891 | 838 | | | |
| 20 | VIEW | | 1 | 37010 | 21741 |00:00:00.12 | 3279 | 0 | | | |
| 21 | WINDOW SORT | | 1 | 37010 | 21741 |00:00:00.11 | 3279 | 0 | 1612K| 624K| 1432K (0)|
| 22 | TABLE ACCESS FULL | VERP_OTM_STAGED_VONS | 1 | 37010 | 21741 |00:00:00.03 | 3279 | 0 | | | |
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Predicate Information (identified by operation id):
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3 - access("S"."VIN"=:B1 AND "S"."STAGE_CODE"='YARD_RECEIPT')
4 - access("VINS"."VIN_SEQUENCE"="VONS"."VON_SEQUENCE" AND "VINS"."PORT_CODE"="VONS"."PORT_CODE" AND "VINS"."INT_COLOR_CODE"="VONS"."INT_COLOR_CODE" AND
"VINS"."EXT_COLOR_CODE"="VONS"."EXT_COLOR_CODE" AND "VINS"."SPEC_CODE"="VONS"."SPEC_CODE" AND "VINS"."OPTION_CODE"="VONS"."OPTION_CODE" AND
"VINS"."MODEL_CODE"="VONS"."MODEL_CODE")
7 - access("C"."PORT"=CASE "VVV"."VEHICLE_SOURCE" WHEN 'SIA' THEN '020' ELSE "from$_subquery$_006"."PORT_CODE" END )
9 - filter("VPT"."PORT"=CASE "VVV"."VEHICLE_SOURCE" WHEN 'SIA' THEN '020' ELSE "from$_subquery$_006"."PORT_CODE" END )
10 - access("VVVP"."VESSEL_PORT_ID"="VVV"."VESSEL_PORT_ID")
12 - access("VVP"."PORT_ID"="VVVP"."PORT_ID")
15 - access("VVV"."SOA_MODEL_CODE"="VPT"."MODEL_CODE" AND "VVV"."SOA_OPTION_CODE"="VPT"."OPTION_CODE" AND "VVV"."SOA_SPEC_CODE"="VPT"."SPEC_CODE" AND
"VVV"."SOA_EXT_COLOR_CODE"="VPT"."EXT_COLOR_CODE" AND "VVV"."SOA_INT_COLOR_CODE"="VPT"."INT_COLOR_CODE")
19 - access("VVV"."PS_STATUS"='NOT_MATCHED')
我很想知道为什么步骤＃6中的WINDOW SORT操作需要如此多的缓冲区获取。对于WINDOW SORT操作，我通常不会看到这种情况。例如，请参阅同一计划的步骤21中的操作 - 不会有额外的缓冲区。
有谁知道这些缓冲区是什么？我怀疑排序操作可能由于其大小而溢出到磁盘，并且额外的缓冲区获取是访问那些临时表空间块。我酌情提供确认或替代解释。感谢。
希望澄清：我想知道为什么步骤6需要添加的缓冲区超出了通过步骤7所需的内容。即，为什么它不像缓冲区在步骤21中获得，这不会增加数量有必要通过第22步。