本地查询计划

EXPLAIN LOCAL （在多节点数据库中）显示分配给每一节点的本地查询计划，它们共同组成整个（全局）查询计划。如果您省略此选项，Vertica 将仅显示全局查询计划。本地查询计划仅以可在 Graphviz 中呈现的 DOT 语言源显示。

例如，以下 EXPLAIN 语句包括 LOCAL 选项：

=> EXPLAIN LOCAL SELECT store_name, store_city, store_state
   FROM store.store_dimension ORDER BY store_state ASC, store_city ASC;

该输出包括 GraphViz 源，用于描述分配给每个节点的本地查询计划。例如，在三节点数据库上，此语句的输出包括一个节点 (v_vmart_node0003) 的以下查询计划的 GraphViz 描述：

 -----------------------------------------------
 PLAN: v_vmart_node0003 (GraphViz Format)
 -----------------------------------------------
 digraph G {
 graph [rankdir=BT, label = "v_vmart_node0003\n", labelloc=t, labeljust=l ordering=out]
 0[label = "NewEENode \nOutBlk=[UncTuple(3)]", color = "green", shape = "box"];
 1[label = "Send\nSend to: v_vmart_node0001\nNet id: 1000\nMerge\n\nUnc: Char(2)\nUnc: Varchar(64)\nUnc: Varchar(64)", color = "green", shape = "box"];
 2[label = "Sort: (keys = A,A,N)\nUnc: Char(2)\nUnc: Varchar(64)\nUnc: Varchar(64)", color = "green", shape = "box"];
 3[label = "ExprEval: \n  store_dimension.store_state\n  store_dimension.store_city\n  store_dimension.store_name\nUnc: Char(2)\nUnc: Varchar(64)\nUnc: Varchar(64)
", color = "green", shape = "box"];
 4[label = "StorageUnionStep: store_dimension_p_b0\nUnc: Varchar(64)\nUnc: Varchar(64)\nUnc: Char(2)", color = "purple", shape = "box"];
 5[label = "ScanStep: store_dimension_p_b0\nstore_key (not emitted)\nstore_name\nstore_city\nstore_state\nUnc: Varchar(64)\nUnc: Varchar(64)\nUnc: Char(2)", color
= "brown", shape = "box"];
 1->0 [label = "0",color = "blue"];
 2->1 [label = "0",color = "blue"];
 3->2 [label = "0",color = "blue"];
 4->3 [label = "0",color = "blue"];
 5->4 [label = "0",color = "blue"];
 }

GraphViz 呈现的此输出如下所示：