Pinot Query Language (PQL)

Learn how to query Pinot using PQL

PQL

PQL is a derivative of SQL that supports selection, projection, aggregation, and grouping aggregation.

PQL Limitations

PQL is only a derivative of SQL, and it does not support Joins nor Subqueries. In order to support them, we suggest to rely on PrestoDB https://prestodb.io/, although Subqueries are not completely supported by PrestoDB at the moment of writing.

PQL Examples

The Pinot Query Language (PQL) is very similar to standard SQL:

SELECT COUNT(*) FROM myTable

Aggregation

SELECT COUNT(*), MAX(foo), SUM(bar) FROM myTable

Grouping on Aggregation

SELECT MIN(foo), MAX(foo), SUM(foo), AVG(foo) FROM myTable
  GROUP BY bar, baz LIMIT 50

Ordering on Aggregation

SELECT MIN(foo), MAX(foo), SUM(foo), AVG(foo) FROM myTable
  GROUP BY bar, baz 
  ORDER BY bar, MAX(foo) DESC LIMIT 50

Filtering

SELECT COUNT(*) FROM myTable
  WHERE foo = 'foo'
  AND bar BETWEEN 1 AND 20
  OR (baz < 42 AND quux IN ('hello', 'goodbye') AND quuux NOT IN (42, 69))

Selection (Projection)

SELECT * FROM myTable
  WHERE quux < 5
  LIMIT 50

Ordering on Selection

SELECT foo, bar FROM myTable
  WHERE baz > 20
  ORDER BY bar DESC
  LIMIT 100

Pagination on Selection

Note: results might not be consistent if column ordered by has same value in multiple rows.

SELECT foo, bar FROM myTable
  WHERE baz > 20
  ORDER BY bar DESC
  LIMIT 50, 100

Wild-card match (in WHERE clause only)

To count rows where the column airlineName starts with U

SELECT count(*) FROM SomeTable
  WHERE regexp_like(airlineName, '^U.*')
  GROUP BY airlineName TOP 10

UDF

As of now, functions have to be implemented within Pinot. Injecting functions is not allowed yet. The example below demonstrate the use of UDFs. More examples in Transform Function in Aggregation Grouping

SELECT count(*) FROM myTable
  GROUP BY dateTimeConvert(timeColumnName, '1:MILLISECONDS:EPOCH', '1:HOURS:EPOCH', '1:HOURS')

BYTES column

Pinot supports queries on BYTES column using HEX string. The query response also uses hex string to represent bytes value.

E.g. the query below fetches all the rows for a given UID.

SELECT * FROM myTable
  WHERE UID = "c8b3bce0b378fc5ce8067fc271a34892"

PQL Specification

SELECT

The select statement is as follows

SELECT <outputColumn> (, outputColumn, outputColumn,...)
  FROM <tableName>
  (WHERE ... | GROUP BY ... | ORDER BY ... | TOP ... | LIMIT ...)

outputColumn can be * to project all columns, columns (foo, bar, baz) or aggregation functions like (MIN(foo), MAX(bar), AVG(baz)).

Filter Functions on Single Value/Multi-value

  • EQUALS

  • IN

  • NOT IN

  • GT

  • LT

  • BETWEEN

  • REGEXP_LIKE

For Multi-Valued columns, EQUALS is similar to CONTAINS.

Supported aggregations on single-value columns

  • COUNT

  • MIN

  • MAX

  • SUM

  • AVG

  • MINMAXRANGE

  • DISTINCT

  • DISTINCTCOUNT

  • DISTINCTCOUNTHLL

  • DISTINCTCOUNTRAWHLL: Returns HLL response serialized as string. The serialized HLL can be converted back into an HLL (see pinot-core/**/HllUtil.java as an example) and then aggregated with other HLLs. A common use case may be to merge HLL responses from different Pinot tables, or to allow aggregation after client-side batching.

  • FASTHLL (WARN: will be deprecated soon. FASTHLL stores serialized HyperLogLog in String format, which performs worse than DISTINCTCOUNTHLL, which supports serialized HyperLogLog in BYTES (byte array) format)

  • PERCENTILE[0-100]: e.g. PERCENTILE5, PERCENTILE50, PERCENTILE99, etc.

  • PERCENTILEEST[0-100]: e.g. PERCENTILEEST5, PERCENTILEEST50, PERCENTILEEST99, etc.

Supported aggregations on multi-value columns

  • COUNTMV

  • MINMV

  • MAXMV

  • SUMMV

  • AVGMV

  • MINMAXRANGEMV

  • DISTINCTCOUNTMV

  • DISTINCTCOUNTHLLMV

  • DISTINCTCOUNTRAWHLLMV: Returns HLL response serialized as string. The serialized HLL can be converted back into an HLL (see pinot-core/**/HllUtil.java as an example) and then aggregated with other HLLs. A common use case may be to merge HLL responses from different Pinot tables, or to allow aggregation after client-side batching.

  • FASTHLLMV (WARN: will be deprecated soon. It does not make lots of sense to configure serialized HyperLogLog column as a dimension)

  • PERCENTILE[0-100]MV: e.g. PERCENTILE5MV, PERCENTILE50MV, PERCENTILE99MV, etc.

  • PERCENTILEEST[0-100]MV: e.g. PERCENTILEEST5MV, PERCENTILEEST50MV, PERCENTILEEST99MV, etc.

WHERE

Supported predicates are comparisons with a constant using the standard SQL operators (=, <, <=, >, >=, <>, ‘!=’) , range comparisons using BETWEEN (foo BETWEEN 42 AND 69), set membership (foo IN (1, 2, 4, 8)) and exclusion (foo NOT IN (1, 2, 4, 8)). For BETWEEN, the range is inclusive.

Comparison with a regular expression is supported using the regexp_like function, as in WHERE regexp_like(columnName, 'regular expression')

GROUP BY

The GROUP BY clause groups aggregation results by a list of columns, or transform functions on columns (see below)

ORDER BY

The ORDER BY clause orders selection results or group by results by a list of columns. PQL supports ordering DESC or ASC.

TOP

The TOP n clause causes the ‘n’ largest group results to be returned. If not specified, the top 10 groups are returned.

LIMIT

The LIMIT n clause causes the selection results to contain at most ‘n’ results. The LIMIT a, b clause paginate the selection results from the ‘a’ th results and return at most ‘b’ results. By default, 10 records are returned in the result.

Transform Function in Aggregation and Grouping

In aggregation and grouping, each column can be transformed from one or multiple columns. For example, the following query will calculate the maximum value of column foo divided by column bar grouping on the column time converted from time unit MILLISECONDS to SECONDS:

SELECT MAX(DIV(foo, bar) FROM myTable
  GROUP BY DATETIMECONVERT(time, '1:MILLISECONDS:EPOCH', '1:SECONDS:EPOCH', '1:SECONDS')

Supported transform functions

Function

Description

ADD

Sum of at least two values

SUB

Difference between two values

MULT

Product of at least two values

DIV

Quotient of two values

MOD

Modulo of two values

ABS

Absolute of a value

CEIL

Rounded up to the nearest integer.

FLOOR

Rounded down to the nearest integer.

EXP

exponential of

LN

Euler’s number raised to the power of x.

SQRT

Square root of a value

TIMECONVERT

Takes 3 arguments, converts the value into another time unit.

Examples TIMECONVERT(time, 'MILLISECONDS', 'SECONDS') - This expression converts the value of column time (taken to be in milliseconds) to the nearest seconds (i.e. the nearest seconds that is lower than the value of date column)

DATETIMECONVERT

Takes 4 arguments, converts the value into another date time format, and buckets time based on the given time granularity.

DATETIMECONVERT(columnName, inputFormat, outputFormat, outputGranularity)where, columnName - column name to convert inputFormat - format of the column columnName outputFormat - format of the result desired after conversion outputGranularity - the granularity in which to bucket the result

Format is expressed as <time size>:<time unit>:<time format>:<pattern> where,

time size - size of the time unit eg: 1, 10

time unit - HOURS, DAYS etc

time format - EPOCH or SIMPLE_DATE_FORMAT

pattern - this is defined in case of SIMPLE_DATE_FORMAT. eg: yyyyMMdd. A specific timezone can be passed using tz(timezone).

timezone - can be expressed as long form tz(Asia/Kolkata), or short form tz(IST) or in terms of GMT tz(GMT+0530). Default is UTC. It is recommended to use long form timezone, as short forms are ambiguous with daylight savings (eg: PDT works during daylight savings, PST otherwise)

Granularity is expressed as <time size>:<time unit>

Examples

1) To convert column "Date" from hoursSinceEpoch to daysSinceEpoch and bucket it to 1 day granularity dateTimeConvert(Date, '1:HOURS:EPOCH', '1:DAYS:EPOCH', '1:DAYS')

2) To simply bucket millis "Date" to 15 minutes granularity dateTimeConvert(Date, '1:MILLISECONDS:EPOCH', '1:MILLISECONDS:EPOCH', '15:MINUTES')

3) To convert column "Date" from hoursSinceEpoch to format yyyyMdd and bucket it to 1 days granularity dateTimeConvert(Date, '1:HOURS:EPOCH', '1:DAYS:SIMPLE_DATE_FORMAT:yyyyMMdd', '1:DAYS')

4) To convert column "Date" from format yyyy/MM/dd to weeksSinceEpoch and bucket it to 1 weeks granularity dateTimeConvert(Date, '1:DAYS:SIMPLE_DATE_FORMAT:yyyy/MM/dd', '1:WEEKS:EPOCH', '1:WEEKS')

5) To convert column "Date" from millis to format yyyyMdd in timezone PST dateTimeConvert(Date, '1:MILLISECONDS:EPOCH', '1:DAYS:SIMPLE_DATE_FORMAT:yyyyMMdd tz(America/Los_Angeles)', '1:DAYS')

DATETRUNC

(Presto) SQL compatible date truncation, equivalent to the Presto function date_trunc. Takes at least 3 and upto 5 arguments, converts the value into a specified output granularity seconds since UTC epoch that is bucketed on a unit in a specified timezone. Examples DATETRUNC('week', time_in_seconds, 'SECONDS') This expression converts the column time_in_seconds, which is a long containing seconds since UTC epoch truncated at WEEK (where a Week starts at Monday UTC midnight). The output is a long seconds since UTC epoch.

DATETRUNC('quarter', DIV(time_milliseconds/1000), 'SECONDS', 'America/Los_Angeles', 'HOURS') This expression converts the expression time_in_milliseconds/1000 (which is thus in seconds) into hours that are truncated at QUARTER at the Los Angeles time zone (where a Quarter begins on 1/1, 4/1, 7/1, 10/1 in Los Angeles timezone). The output is expressed as hours since UTC epoch (note that the output is not Los Angeles timezone)

ARRAYLENGTH

Returns the length of a multi-value column

VALUEIN

Takes at least 2 arguments, where the first argument is a multi-valued column, and the following arguments are constant values. The transform function will filter the value from the multi-valued column with the given constant values. The VALUEIN transform function is especially useful when the same multi-valued column is both filtering column and grouping column. Examples VALUEIN(mvColumn, 3, 5, 15)

JSONEXTRACTSCALAR

JSONEXTRACTSCALAR(jsonField, 'jsonPath', 'resultsType')evaluates the jsonPath on jsonField (a string containing JSON) and returns the result as a type resultsType

jsonFieldName is a String field with Json document.

jsonPath is a JsonPath expression to read from JSON document

results_type refers to the results data type, could be INT, LONG, FLOAT, DOUBLE, STRING, INT_ARRAY, LONG_ARRAY, FLOAT_ARRAY, DOUBLE_ARRAY, STRING_ARRAY.

Examples

JSONEXTRACTSCALAR(profile_json_str, '$.name', 'STRING') -> "bob"

JSONEXTRACTSCALAR(profile_json_str, '$.age', 'INT') -> 37

JSONEXTRACTKEY

JSONEXTRACTKEY(jsonField, 'jsonPath') extracts all field names based on jsonPath as a STRING_ARRAY.

jsonFieldName is a String field with Json document.

jsonPath is a JsonPath expression to read from JSON document

Examples

JSONEXTRACTSCALAR(profile_json_str, '$.*') -> ["name", "age", "phone"...]

Differences with SQL

These differences only apply to the PQL endpoint. They do not hold true for the standard-SQL endpoint, which is the recommended endpoint. More information about the two types of endpoints in Querying Pinot

  • TOP works like LIMIT for truncation in group by queries

  • No need to select the columns to group with. The following two queries are both supported in PQL, where the non-aggregation columns are ignored.

SELECT MIN(foo), MAX(foo), SUM(foo), AVG(foo) FROM mytable
  GROUP BY bar, baz
  TOP 50

SELECT bar, baz, MIN(foo), MAX(foo), SUM(foo), AVG(foo) FROM mytable
  GROUP BY bar, baz
  TOP 50

  • The results will always order by the aggregated value (descending). The results for query

SELECT MIN(foo), MAX(foo) FROM myTable
  GROUP BY bar
  TOP 50

will be the same as the combining results from the following queries

SELECT MIN(foo) FROM myTable
  GROUP BY bar
  TOP 50
SELECT MAX(foo) FROM myTable
  GROUP BY bar
  TOP 50

where we don’t put the results for the same group together.

  • No support for ORDER BY in aggregation group by. However, ORDER BY support was added recently and is available in the standard-SQL endpoint. It can be used in the PQL endpoint by passing queryOptions into the payload as follows

{
  "pql" : "SELECT SUM(foo), SUM(bar) from myTable GROUP BY moo ORDER BY SUM(bar) ASC, moo DESC TOP 10",
  "queryOptions" : "groupByMode=sql;responseFormat=sql"
}

where,

  • groupByMode=sql - standard sql way of execution group by, hence accepting order by

  • responseFormat=sql - standard sql way of displaying results, in a tabular manner

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