| (window.webpackJsonp=window.webpackJsonp||[]).push([[35],{600:function(e,t,a){"use strict";a.r(t);var s=a(69),n=Object(s.a)({},(function(){var e=this,t=e.$createElement,a=e._self._c||t;return a("ContentSlotsDistributor",{attrs:{"slot-key":e.$parent.slotKey}},[a("h1",{attrs:{id:"downsampling-query"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#downsampling-query"}},[e._v("#")]),e._v(" Downsampling query")]),e._v(" "),a("ul",[a("li",[e._v("org.apache.iotdb.db.query.dataset.groupby.GroupByEngineDataSet")])]),e._v(" "),a("p",[e._v("The result set of the downsampling query will inherit "),a("code",[e._v("GroupByEngineDataSet")]),e._v(", this class contains the following fields:")]),e._v(" "),a("ul",[a("li",[e._v("protected long queryId")]),e._v(" "),a("li",[e._v("private long interval")]),e._v(" "),a("li",[e._v("private long slidingStep")])]),e._v(" "),a("p",[e._v("The following two fields are for the entire query, and the time period is left closed and right open, which is "),a("code",[e._v("[startTime, endTime)")]),e._v(":")]),e._v(" "),a("ul",[a("li",[e._v("private long startTime")]),e._v(" "),a("li",[e._v("private long endTime")])]),e._v(" "),a("p",[e._v("The following fields are for the current segment, and the time period is left closed and right open, which is "),a("code",[e._v("[startTime, endTime)")]),e._v(":")]),e._v(" "),a("ul",[a("li",[e._v("protected long curStartTime;")]),e._v(" "),a("li",[e._v("protected long curEndTime;")]),e._v(" "),a("li",[e._v("private int usedIndex;")]),e._v(" "),a("li",[e._v("protected boolean hasCachedTimeInterval;")])]),e._v(" "),a("p",[e._v("The core method of "),a("code",[e._v("GroupByEngineDataSet")]),e._v(" is very easy. 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Its main logic is:")]),e._v(" "),a("div",{staticClass:"language- line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-text"}},[a("code",[e._v("//Calculate the data left over from the last time, and end the calculation if you can get the results directly\nif (calcFromCacheData()) {\n return results;\n}\n\n//Because a chunk contains multiple pages, the page of the current chunk must be used up before the next chunk is opened.\nif (readAndCalcFromPage()) {\n return results;\n}\n\n//If the remaining data is calculated, open a new chunk to continue the calculation.\nwhile (reader.hasNextChunk()) {\n Statistics chunkStatistics = reader.currentChunkStatistics();\n // Determine if Statistics is available and perform calculations\n ....\n // Skip current chunk\n reader.skipCurrentChunk();\n // End calculation if all results have been obtained\n if (isEndCalc()) {\n return true;\n }\n continue;\n }\n //If you cannot use chunkStatistics, you need to use page data to calculate\n if (readAndCalcFromPage()) {\n return results;\n }\n}\n")])]),e._v(" "),a("div",{staticClass:"line-numbers-wrapper"},[a("span",{staticClass:"line-number"},[e._v("1")]),a("br"),a("span",{staticClass:"line-number"},[e._v("2")]),a("br"),a("span",{staticClass:"line-number"},[e._v("3")]),a("br"),a("span",{staticClass:"line-number"},[e._v("4")]),a("br"),a("span",{staticClass:"line-number"},[e._v("5")]),a("br"),a("span",{staticClass:"line-number"},[e._v("6")]),a("br"),a("span",{staticClass:"line-number"},[e._v("7")]),a("br"),a("span",{staticClass:"line-number"},[e._v("8")]),a("br"),a("span",{staticClass:"line-number"},[e._v("9")]),a("br"),a("span",{staticClass:"line-number"},[e._v("10")]),a("br"),a("span",{staticClass:"line-number"},[e._v("11")]),a("br"),a("span",{staticClass:"line-number"},[e._v("12")]),a("br"),a("span",{staticClass:"line-number"},[e._v("13")]),a("br"),a("span",{staticClass:"line-number"},[e._v("14")]),a("br"),a("span",{staticClass:"line-number"},[e._v("15")]),a("br"),a("span",{staticClass:"line-number"},[e._v("16")]),a("br"),a("span",{staticClass:"line-number"},[e._v("17")]),a("br"),a("span",{staticClass:"line-number"},[e._v("18")]),a("br"),a("span",{staticClass:"line-number"},[e._v("19")]),a("br"),a("span",{staticClass:"line-number"},[e._v("20")]),a("br"),a("span",{staticClass:"line-number"},[e._v("21")]),a("br"),a("span",{staticClass:"line-number"},[e._v("22")]),a("br"),a("span",{staticClass:"line-number"},[e._v("23")]),a("br"),a("span",{staticClass:"line-number"},[e._v("24")]),a("br"),a("span",{staticClass:"line-number"},[e._v("25")]),a("br"),a("span",{staticClass:"line-number"},[e._v("26")]),a("br"),a("span",{staticClass:"line-number"},[e._v("27")]),a("br"),a("span",{staticClass:"line-number"},[e._v("28")]),a("br")])]),a("p",[e._v("The "),a("code",[e._v("readAndCalcFromPage")]),e._v(" method is to obtain the page data from the currently opened chunk and calculate the aggregate result. Returns true when all calculations are completed, otherwise returns false. The main logic:")]),e._v(" "),a("div",{staticClass:"language- line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-text"}},[a("code",[e._v("while (reader.hasNextPage()) {\n Statistics pageStatistics = reader.currentPageStatistics();\n //PageStatistics can only be used if the page does not intersect with other pages\n if (pageStatistics != null) {\n // Determine if Statistics is available and perform calculations\n ....\n // Skip current page\n reader.skipCurrentPage();\n // End calculation if all results have been obtained\n if (isEndCalc()) {\n return true;\n }\n continue;\n }\n }\n // When Statistics is not available, you can only fetch all data for calculation\n BatchData batchData = reader.nextPage();\n if (batchData == null || !batchData.hasCurrent()) {\n continue;\n }\n // If the page just opened exceeds the time range, the data retrieved is cached and the calculation is directly ended.\n if (batchData.currentTime() >= curEndTime) {\n preCachedData = batchData;\n return true;\n }\n //Perform calculations\n calcFromBatch(batchData);\n ...\n}\n\n")])]),e._v(" "),a("div",{staticClass:"line-numbers-wrapper"},[a("span",{staticClass:"line-number"},[e._v("1")]),a("br"),a("span",{staticClass:"line-number"},[e._v("2")]),a("br"),a("span",{staticClass:"line-number"},[e._v("3")]),a("br"),a("span",{staticClass:"line-number"},[e._v("4")]),a("br"),a("span",{staticClass:"line-number"},[e._v("5")]),a("br"),a("span",{staticClass:"line-number"},[e._v("6")]),a("br"),a("span",{staticClass:"line-number"},[e._v("7")]),a("br"),a("span",{staticClass:"line-number"},[e._v("8")]),a("br"),a("span",{staticClass:"line-number"},[e._v("9")]),a("br"),a("span",{staticClass:"line-number"},[e._v("10")]),a("br"),a("span",{staticClass:"line-number"},[e._v("11")]),a("br"),a("span",{staticClass:"line-number"},[e._v("12")]),a("br"),a("span",{staticClass:"line-number"},[e._v("13")]),a("br"),a("span",{staticClass:"line-number"},[e._v("14")]),a("br"),a("span",{staticClass:"line-number"},[e._v("15")]),a("br"),a("span",{staticClass:"line-number"},[e._v("16")]),a("br"),a("span",{staticClass:"line-number"},[e._v("17")]),a("br"),a("span",{staticClass:"line-number"},[e._v("18")]),a("br"),a("span",{staticClass:"line-number"},[e._v("19")]),a("br"),a("span",{staticClass:"line-number"},[e._v("20")]),a("br"),a("span",{staticClass:"line-number"},[e._v("21")]),a("br"),a("span",{staticClass:"line-number"},[e._v("22")]),a("br"),a("span",{staticClass:"line-number"},[e._v("23")]),a("br"),a("span",{staticClass:"line-number"},[e._v("24")]),a("br"),a("span",{staticClass:"line-number"},[e._v("25")]),a("br"),a("span",{staticClass:"line-number"},[e._v("26")]),a("br"),a("span",{staticClass:"line-number"},[e._v("27")]),a("br"),a("span",{staticClass:"line-number"},[e._v("28")]),a("br"),a("span",{staticClass:"line-number"},[e._v("29")]),a("br"),a("span",{staticClass:"line-number"},[e._v("30")]),a("br")])]),a("p",[e._v("The "),a("code",[e._v("calcFromBatch")]),e._v(" method is to traverse all the aggregate functions to calculate the retrieved BatchData. The main logic is:")]),e._v(" "),a("div",{staticClass:"language- line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-text"}},[a("code",[e._v("for (Pair<AggregateResult, Integer> result : results) {\n //If a function has already been calculated, it will not be calculated, such as the minimum calculation.\n if (result.left.isCalculatedAggregationResult()) {\n continue;\n }\n // Perform calculations\n ....\n}\n//Determine if the data in the current batchdata can still be used next time, if it can be added to the cache\nif (batchData.getMaxTimestamp() >= curEndTime) {\n preCachedData = batchData;\n}\n")])]),e._v(" "),a("div",{staticClass:"line-numbers-wrapper"},[a("span",{staticClass:"line-number"},[e._v("1")]),a("br"),a("span",{staticClass:"line-number"},[e._v("2")]),a("br"),a("span",{staticClass:"line-number"},[e._v("3")]),a("br"),a("span",{staticClass:"line-number"},[e._v("4")]),a("br"),a("span",{staticClass:"line-number"},[e._v("5")]),a("br"),a("span",{staticClass:"line-number"},[e._v("6")]),a("br"),a("span",{staticClass:"line-number"},[e._v("7")]),a("br"),a("span",{staticClass:"line-number"},[e._v("8")]),a("br"),a("span",{staticClass:"line-number"},[e._v("9")]),a("br"),a("span",{staticClass:"line-number"},[e._v("10")]),a("br"),a("span",{staticClass:"line-number"},[e._v("11")]),a("br"),a("span",{staticClass:"line-number"},[e._v("12")]),a("br")])]),a("h2",{attrs:{id:"aggregated-query-with-value-filter"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#aggregated-query-with-value-filter"}},[e._v("#")]),e._v(" Aggregated query with value filter")]),e._v(" "),a("p",[e._v("The downsampling query logic with value filtering conditions is mainly in the "),a("code",[e._v("GroupByWithValueFilterDataSet")]),e._v(" class, which inherits "),a("code",[e._v("GroupByEngineDataSet")]),e._v(".")]),e._v(" "),a("p",[e._v("This class has the following key fields:")]),e._v(" "),a("ul",[a("li",[e._v("private List<IReaderByTimestamp> allDataReaderList")]),e._v(" "),a("li",[e._v("private GroupByPlan groupByTimePlan")]),e._v(" "),a("li",[e._v("private TimeGenerator timestampGenerator")]),e._v(" "),a("li",[e._v("private long timestamp is used to cache timestamp for the next group by partition")]),e._v(" "),a("li",[e._v("private boolean hasCachedTimestamp used to determine whether there is a timestamp cache for the next group by partition")]),e._v(" "),a("li",[e._v("private int timeStampFetchSize is the size of the group by calculating the batch")])]),e._v(" "),a("p",[e._v("First, in the initialization "),a("code",[e._v("initGroupBy ()")]),e._v("method, create a "),a("code",[e._v("timestampGenerator")]),e._v(" based on the expression; then create a "),a("code",[e._v("SeriesReaderByTimestamp")]),e._v(" for each time series and place it in the "),a("code",[e._v("allDataReaderList")]),e._v(" list. After initialization is complete, call the "),a("code",[e._v("nextWithoutConstraint ()")]),e._v("method to update the result. If timestamp is cached for the next group by partition and the time meets the requirements, add it to "),a("code",[e._v("timestampArray")]),e._v(", otherwise return the "),a("code",[e._v("aggregateResultList")]),e._v(" result directly; if timestamp is not cached for the next group by partition, use "),a("code",[e._v("timestampGenerator")]),e._v(" to traverse:")]),e._v(" "),a("div",{staticClass:"language- line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-text"}},[a("code",[e._v("while (timestampGenerator.hasNext()) {\n // Call constructTimeArrayForOneCal () method to get a list of timestamp\n timeArrayLength = constructTimeArrayForOneCal(timestampArray, timeArrayLength);\n\n // Call the updateResultUsingTimestamps () method to calculate the aggregate result using the timestamp list\n for (int i = 0; i < paths.size(); i++) {\n aggregateResultList.get(i).updateResultUsingTimestamps(\n timestampArray, timeArrayLength, allDataReaderList.get(i));\n }\n\n timeArrayLength = 0;\n // Determine if it is over\n if (timestamp >= curEndTime) {\n hasCachedTimestamp = true;\n break;\n }\n}\n")])]),e._v(" "),a("div",{staticClass:"line-numbers-wrapper"},[a("span",{staticClass:"line-number"},[e._v("1")]),a("br"),a("span",{staticClass:"line-number"},[e._v("2")]),a("br"),a("span",{staticClass:"line-number"},[e._v("3")]),a("br"),a("span",{staticClass:"line-number"},[e._v("4")]),a("br"),a("span",{staticClass:"line-number"},[e._v("5")]),a("br"),a("span",{staticClass:"line-number"},[e._v("6")]),a("br"),a("span",{staticClass:"line-number"},[e._v("7")]),a("br"),a("span",{staticClass:"line-number"},[e._v("8")]),a("br"),a("span",{staticClass:"line-number"},[e._v("9")]),a("br"),a("span",{staticClass:"line-number"},[e._v("10")]),a("br"),a("span",{staticClass:"line-number"},[e._v("11")]),a("br"),a("span",{staticClass:"line-number"},[e._v("12")]),a("br"),a("span",{staticClass:"line-number"},[e._v("13")]),a("br"),a("span",{staticClass:"line-number"},[e._v("14")]),a("br"),a("span",{staticClass:"line-number"},[e._v("15")]),a("br"),a("span",{staticClass:"line-number"},[e._v("16")]),a("br"),a("span",{staticClass:"line-number"},[e._v("17")]),a("br")])]),a("p",[e._v("The "),a("code",[e._v("constructTimeArrayForOneCal ()")]),e._v("method traverses timestampGenerator to build a list of timestamps:")]),e._v(" "),a("div",{staticClass:"language- line-numbers-mode"},[a("pre",{pre:!0,attrs:{class:"language-text"}},[a("code",[e._v("for (int cnt = 1; cnt < timeStampFetchSize && timestampGenerator.hasNext(); cnt++) {\n timestamp = timestampGenerator.next();\n if (timestamp < curEndTime) {\n timestampArray[timeArrayLength++] = timestamp;\n } else {\n hasCachedTimestamp = true;\n break;\n }\n}\n")])]),e._v(" "),a("div",{staticClass:"line-numbers-wrapper"},[a("span",{staticClass:"line-number"},[e._v("1")]),a("br"),a("span",{staticClass:"line-number"},[e._v("2")]),a("br"),a("span",{staticClass:"line-number"},[e._v("3")]),a("br"),a("span",{staticClass:"line-number"},[e._v("4")]),a("br"),a("span",{staticClass:"line-number"},[e._v("5")]),a("br"),a("span",{staticClass:"line-number"},[e._v("6")]),a("br"),a("span",{staticClass:"line-number"},[e._v("7")]),a("br"),a("span",{staticClass:"line-number"},[e._v("8")]),a("br"),a("span",{staticClass:"line-number"},[e._v("9")]),a("br")])]),a("h2",{attrs:{id:"aggregated-query-with-level"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#aggregated-query-with-level"}},[e._v("#")]),e._v(" Aggregated query with level")]),e._v(" "),a("p",[e._v("After down-frequency query, we could also to count the total number of points of")]),e._v(" "),a("p",[e._v("each node at the given level in current Metadata Tree.")]),e._v(" "),a("p",[e._v("The logic is in the "),a("code",[e._v("GroupByTimeDataSet")]),e._v(" class.")]),e._v(" "),a("ol",[a("li",[a("p",[e._v("In the beginning, get the final paths group by level and the origin path index to final path.")]),e._v(" "),a("blockquote",[a("p",[e._v("For example, we could get final path "),a("code",[e._v("root.sg1")]),e._v(" by "),a("code",[e._v("root.sg1.d1.s0,root.sg1.d2.s1")]),e._v(" and "),a("code",[e._v("level=1")]),e._v(".")])])]),e._v(" "),a("li",[a("p",[e._v("Then, get the down-frequency query result: RowRecord.")])]),e._v(" "),a("li",[a("p",[e._v("Finally, merge each RowRecord to NewRecord, which has fields like <final path, count>.")]),e._v(" "),a("blockquote",[a("p",[e._v("For example, we will get new RowRecord "),a("code",[e._v("<root.sg1,7>")]),e._v(" by "),a("code",[e._v("<root.sg1.d1.s0, 3>, <root.sg1.d2.s1, 4>")]),e._v(" and level=1.")])])])]),e._v(" "),a("blockquote",[a("p",[e._v("Attention:")]),e._v(" "),a("ol",[a("li",[e._v("only support count aggregation")]),e._v(" "),a("li",[e._v("root's level == 0")])])])])}),[],!1,null,null,null);t.default=n.exports}}]); |