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入口,sql /** * Executes a SQL query using Spark, returning the result as a `DataFrame`. * This API eagerly runs DDL/DML commands, but not for SELECT que 阅读全文
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Introduction Big data applications require a mix of processing techniques, data sources and storage formats. The earliest systems designed for these w 阅读全文
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INTRODUCTION Estimating the selectivity of a query—the fraction of input tuples that satisfy the query’s predicate—is a fundamental component in cost- 阅读全文
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Oracle的SQL引擎大体分为这几部分, (1)首先要进入Prepare的阶段,Parser,SA和TC A SQL statement goes through the Parser, Semantic Analysis (SA), and Type-Check (TC) first befor 阅读全文
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Why Key Components in Optimizer are Still Not Accurate? In this section, we summarize the reasons why the cardinality estimation, cost model, and plan 阅读全文
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INTRODUCTION The Needs of IoT systems 正对IoT系统的以下4点需求,高吞吐,有效存储,实时查询和高可用,当前的系统无法比较好的解决。 With the rapid proliferation(rapid increase in numbers) of conne 阅读全文
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INTRODUCTION The problem of finding a good join order is one of the most studied problems in the database field. Figure 1 illustrates the classical, c 阅读全文