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Data Engineering
Join discussions on data engineering best practices, architectures, and optimization strategies within the Databricks Community. Exchange insights and solutions with fellow data engineers.
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chhavibansal
by • New Contributor III
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What is the upper bound limit for dataSkippingNumIndexedCols, to keeps stats in delta log file?

Is there an upper bound of number that i can assign to delta.dataSkippingNumIndexedCols for computing statistics. Is there some tradeoff benchmark available for increasing this number beyond 32.

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Anonymous
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@Chhavi Bansal​ :The delta.dataSkippingNumIndexedCols configuration property controls the maximum number of columns that Delta Lake will build statistics on during data skipping. By default, this value is set to 32. There is no hard upper bound on th...

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chhavibansal
by • New Contributor III
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ANALYZE TABLE showing NULLs for all statistics in Spark

var df2 = spark.read .format("csv") .option("sep", ",") .option("header", "true") .option("inferSchema", "true") .load("src/main/resources/datasets/titanic.csv")   df2.createOrReplaceTempView("titanic") spark.table("titanic").cach...

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chhavibansal
New Contributor III
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can you share what the *newtitanic* is I think that you would have done something similarspark.sql("create table newtitanic as select * from titanic")something like this works for me, but the issue is i first make a temp view then again create a tab...

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aladda
by • Databricks Employee
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Resolved! How are stats collected on a Delta column utilized

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aladda
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Stats collected on a Delta column are either using for Partitioning Pruning, Data Skipping. See here - https://docs.databricks.com/delta/optimizations/file-mgmt.html#delta-data-skipping for detailsIn additional stats are also used for Metadata only q...

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aladda
by • Databricks Employee
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Resolved! How many columns does Delta Engine collect stats on for a Delta Table

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aladda
Databricks Employee
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by default a delta table has stats collected on the first 32 columns. This setting can be configured using the following.set spark.databricks.delta.properties.defaults.dataSkippingNumIndexedCols = 3However there's a time trade-off to having a large n...

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dshosseinyousef
by • New Contributor II
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how to Calculate quantile on grouped data in spark Dataframe

I have the following sparkdataframe : agent_id/ payment_amount a /1000 b /1100 a /1100 a /1200 b /1200 b /1250 a /10000 b /9000 my desire output would be something like <code>agen_id 95_quantile a whatever is95 quantile for a...

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Weiluo__David_R
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For those of you who haven't run into this SO thread http://stackoverflow.com/questions/39633614/calculate-quantile-on-grouped-data-in-spark-dataframe, it's pointed out there that one work-around is to use HIVE UDF "percentile_approx". Please see th...

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