Package org.apache.flink.table.api

Class Expressions

java.lang.Object
org.apache.flink.table.api.Expressions
@PublicEvolving public final class Expressions extends Object
Entry point of the Table API Expression DSL such as: $("myField").plus(10).abs()

This class contains static methods for referencing table columns, creating literals, and building more complex Expression chains. ApiExpressions are pure API entities that are further translated into ResolvedExpressions under the hood.

For fluent definition of expressions and easier readability, we recommend adding a star import to the methods of this class: 

 import static org.apache.flink.table.api.Expressions.*;

Check the documentation for more programming language specific APIs, for example, by using Scala implicits.

  • Field Details

    • UNBOUNDED_ROW

      public static final ApiExpression UNBOUNDED_ROW
      Offset constant to be used in the preceding clause of unbounded Over windows. Use this constant for a time interval. Unbounded over windows start with the first row of a partition.

    • UNBOUNDED_RANGE

      public static final ApiExpression UNBOUNDED_RANGE
      Offset constant to be used in the preceding clause of unbounded Over windows. Use this constant for a row-count interval. Unbounded over windows start with the first row of a partition.

    • CURRENT_ROW

      public static final ApiExpression CURRENT_ROW
      Offset constant to be used in the following clause of Over windows. Use this for setting the upper bound of the window to the current row.

    • CURRENT_RANGE

      public static final ApiExpression CURRENT_RANGE
      Offset constant to be used in the following clause of Over windows. Use this for setting the upper bound of the window to the sort key of the current row, i.e., all rows with the same sort key as the current row are included in the window.

  • Constructor Details

    • Expressions

      public Expressions()

  • Method Details

    • $

      public static ApiExpression $(String name)
      Creates an unresolved reference to a table's column.

      Example: 

      
 tab.select($("key"), $("value"))
      See Also:

    • col

      public static ApiExpression col(String name)
      Creates an unresolved reference to a table's column.

      Because $(String) is not supported by every JVM language due to the dollar sign, this method provides a synonym with the same behavior.

      Example: 

      
 tab.select(col("key"), col("value"))
      See Also:

    • lit

      public static ApiExpression lit(Object v)
      Creates a SQL literal.

      The data type is derived from the object's class and its value.

      For example:

      • lit(12) leads to INT
      • lit("abc") leads to CHAR(3)
      • lit(new BigDecimal("123.45")) leads to DECIMAL(5, 2)

      See ValueDataTypeConverter for a list of supported literal values.

    • lit

      public static ApiExpression lit(Object v, org.apache.flink.table.types.DataType dataType)
      Creates a SQL literal of a given DataType.

      The method lit(Object) is preferred as it extracts the DataType automatically. Use this method only when necessary. The class of v must be supported according to the LogicalType.supportsInputConversion(Class).

    • range

      public static ApiExpression range(String start, String end)
      Indicates a range from 'start' to 'end', which can be used in columns selection.

      Example: 

      
 Table table = ...
 table.select(withColumns(range(b, c)))
      See Also:

    • range

      public static ApiExpression range(int start, int end)
      Indicates an index based range, which can be used in columns selection.

      Example: 

      
 Table table = ...
 table.select(withColumns(range(3, 4)))
      See Also:

    • and

      public static ApiExpression and(Object predicate0, Object predicate1, Object... predicates)
      Boolean AND in three-valued logic.

    • or

      public static ApiExpression or(Object predicate0, Object predicate1, Object... predicates)
      Boolean OR in three-valued logic.

    • not

      public static ApiExpression not(Object expression)
      Inverts a given boolean expression.

      This method supports a three-valued logic by preserving NULL. This means if the input expression is NULL, the result will also be NULL.

      The resulting type is nullable if and only if the input type is nullable.

      Examples: 

      
 not(lit(true)) // false
 not(lit(false)) // true
 not(lit(null, DataTypes.BOOLEAN())) // null

    • currentDate

      public static ApiExpression currentDate()
      Returns the current SQL date in local time zone, the return type of this expression is DataTypes.DATE().

    • currentTime

      public static ApiExpression currentTime()
      Returns the current SQL time in local time zone, the return type of this expression is DataTypes.TIME().

    • currentTimestamp

      public static ApiExpression currentTimestamp()
      Returns the current SQL timestamp in local time zone, the return type of this expression is DataTypes.TIMESTAMP_WITH_LOCAL_TIME_ZONE().

    • currentWatermark

      public static ApiExpression currentWatermark(Object rowtimeAttribute)
      Returns the current watermark for the given rowtime attribute, or NULL if no common watermark of all upstream operations is available at the current operation in the pipeline.

      The function returns the watermark with the same type as the rowtime attribute, but with an adjusted precision of 3. For example, if the rowtime attribute is TIMESTAMP_LTZ(9), the function will return TIMESTAMP_LTZ(3).

      If no watermark has been emitted yet, the function will return NULL. Users must take care of this when comparing against it, e.g. in order to filter out late data you can use 

      
 WHERE CURRENT_WATERMARK(ts) IS NULL OR ts > CURRENT_WATERMARK(ts)

    • currentDatabase

      public static ApiExpression currentDatabase()
      Return the current database, the return type of this expression is DataTypes.STRING().

    • localTime

      public static ApiExpression localTime()
      Returns the current SQL time in local time zone, the return type of this expression is DataTypes.TIME(), this is a synonym for currentTime().

    • localTimestamp

      public static ApiExpression localTimestamp()
      Returns the current SQL timestamp in local time zone, the return type of this expression is DataTypes.TIMESTAMP().

    • toDate

      public static ApiExpression toDate(Object dateStr)
      Converts the given date string with format 'yyyy-MM-dd' to DataTypes.DATE().
      Parameters:
      dateStr - The date string.
      Returns:
      The date value of DataTypes.DATE() type.

    • toDate

      public static ApiExpression toDate(Object dateStr, Object format)
      Converts the date string with the specified format to DataTypes.DATE().
      Parameters:
      dateStr - The date string.
      format - The format of the string.
      Returns:
      The date value of DataTypes.DATE() type.

    • toTimestamp

      public static ApiExpression toTimestamp(Object timestampStr)
      Converts the given date time string with format 'yyyy-MM-dd HH:mm:ss' under the 'UTC+0' time zone to DataTypes.TIMESTAMP().
      Parameters:
      timestampStr - The date time string.
      Returns:
      The timestamp value with DataTypes.TIMESTAMP() type.

    • toTimestamp

      public static ApiExpression toTimestamp(Object timestampStr, Object format)
      Converts the given time string with the specified format under the 'UTC+0' time zone to DataTypes.TIMESTAMP().
      Parameters:
      timestampStr - The date time string.
      format - The format of the string.
      Returns:
      The timestamp value with DataTypes.TIMESTAMP() type.

    • toTimestampLtz

      public static ApiExpression toTimestampLtz(Object numericEpochTime, Object precision)
      Converts a numeric type epoch time to DataTypes.TIMESTAMP_LTZ(int).

      The supported precision is 0 or 3:

      • 0 means the numericEpochTime is in second.
      • 3 means the numericEpochTime is in millisecond.
      Parameters:
      numericEpochTime - The epoch time with numeric type.
      precision - The precision to indicate the epoch time is in second or millisecond.
      Returns:
      The timestamp value with DataTypes.TIMESTAMP_LTZ(int) type.

    • toTimestampLtz

      public static ApiExpression toTimestampLtz(String timestampStr, String format)
      Converts the given time string with the specified format to DataTypes.TIMESTAMP_LTZ(int).
      Parameters:
      timestampStr - The timestamp string to convert.
      format - The format of the string.
      Returns:
      The timestamp value with DataTypes.TIMESTAMP_LTZ(int) type.

    • toTimestampLtz

      public static ApiExpression toTimestampLtz(String timeStamp)
      Converts a timestamp to DataTypes.TIMESTAMP_LTZ(int).

      This method takes a string representing a timestamp and converts it to a TIMESTAMP_LTZ using the built-in TO_TIMESTAMP_LTZ function definition.

      Parameters:
      timeStamp - The timestamp string to be converted.
      Returns:
      The timestamp value with DataTypes.TIMESTAMP_LTZ(int) type.

    • toTimestampLtz

      public static ApiExpression toTimestampLtz(Object numericEpochTime)
      Converts a numeric type epoch time to DataTypes.TIMESTAMP_LTZ(int).

      This method takes an object representing an epoch time and converts it to a TIMESTAMP_LTZ using the built-in TO_TIMESTAMP_LTZ function definition.

      Parameters:
      numericEpochTime - The epoch time with numeric type.
      Returns:
      The timestamp value with DataTypes.TIMESTAMP_LTZ(int) type.

    • toTimestampLtz

      public static ApiExpression toTimestampLtz(Object timestampStr, Object format, Object timezone)
      Converts a string timestamp with the custom format and timezone to DataTypes.TIMESTAMP_LTZ(int).

      The timestamp string will be parsed using the custom format and timezone, and converted to a TIMESTAMP_LTZ value.

      Parameters:
      timestampStr - The timestamp string to convert.
      format - The format pattern to parse the timestamp string.
      timezone - The timezone to use for the conversion.
      Returns:
      The timestamp value with DataTypes.TIMESTAMP_LTZ(int) type.

    • temporalOverlaps

      public static ApiExpression temporalOverlaps(Object leftTimePoint, Object leftTemporal, Object rightTimePoint, Object rightTemporal)
      Determines whether two anchored time intervals overlap. Time point and temporal are transformed into a range defined by two time points (start, end). The function evaluates leftEnd >= rightStart && rightEnd >= leftStart.

      It evaluates: leftEnd >= rightStart && rightEnd >= leftStart

      e.g. 

      
 temporalOverlaps(
      lit("2:55:00").toTime(),
      lit(1).hours(),
      lit("3:30:00").toTime(),
      lit(2).hours()
 )

      leads to true

    • dateFormat

      public static ApiExpression dateFormat(Object timestamp, Object format)
      Formats a timestamp as a string using a specified format. The format must be compatible with MySQL's date formatting syntax as used by the date_parse function.

      For example dataFormat($("time"), "%Y, %d %M") results in strings formatted as "2017, 05 May".

      Parameters:
      timestamp - The timestamp to format as string.
      format - The format of the string.
      Returns:
      The formatted timestamp as string.

    • timestampDiff

      public static ApiExpression timestampDiff(org.apache.flink.table.expressions.TimePointUnit timePointUnit, Object timePoint1, Object timePoint2)
      Returns the (signed) number of TimePointUnit between timePoint1 and timePoint2.

      For example, timestampDiff(TimePointUnit.DAY, lit("2016-06-15").toDate(), lit("2016-06-18").toDate() leads to 3.

      Parameters:
      timePointUnit - The unit to compute diff.
      timePoint1 - The first point in time.
      timePoint2 - The second point in time.
      Returns:
      The number of intervals as integer value.

    • convertTz

      public static ApiExpression convertTz(Object dateStr, Object tzFrom, Object tzTo)
      Converts a datetime dateStr (with default ISO timestamp format 'yyyy-MM-dd HH:mm:ss') from time zone tzFrom to time zone tzTo. The format of time zone should be either an abbreviation such as "PST", a full name such as "America/Los_Angeles", or a custom ID such as "GMT-08:00". E.g., convertTz('1970-01-01 00:00:00', 'UTC', 'America/Los_Angeles') returns '1969-12-31 16:00:00'.
      Parameters:
      dateStr - the date time string
      tzFrom - the original time zone
      tzTo - the target time zone
      Returns:
      The formatted timestamp as string.

    • fromUnixtime

      public static ApiExpression fromUnixtime(Object unixtime)
      Converts unix timestamp (seconds since '1970-01-01 00:00:00' UTC) to datetime string in the "yyyy-MM-dd HH:mm:ss" format.
      Parameters:
      unixtime - The unix timestamp with numeric type.
      Returns:
      The formatted timestamp as string.

    • fromUnixtime

      public static ApiExpression fromUnixtime(Object unixtime, Object format)
      Converts unix timestamp (seconds since '1970-01-01 00:00:00' UTC) to datetime string in the given format.
      Parameters:
      unixtime - The unix timestamp with numeric type.
      format - The format of the string.
      Returns:
      The formatted timestamp as string.

    • unixTimestamp

      public static ApiExpression unixTimestamp()
      Gets the current unix timestamp in seconds. This function is not deterministic which means the value would be recalculated for each record.
      Returns:
      The current unix timestamp as bigint.

    • unixTimestamp

      public static ApiExpression unixTimestamp(Object timestampStr)
      Converts the given date time string with format 'yyyy-MM-dd HH:mm:ss' to unix timestamp (in seconds), using the time zone specified in the table config.
      Parameters:
      timestampStr - The date time string.
      Returns:
      The converted timestamp as bigint.

    • unixTimestamp

      public static ApiExpression unixTimestamp(Object timestampStr, Object format)
      Converts the given date time string with the specified format to unix timestamp (in seconds), using the specified timezone in table config.
      Parameters:
      timestampStr - The date time string.
      format - The format of the date time string.
      Returns:
      The converted timestamp as bigint.

    • array

      public static ApiExpression array(Object head, Object... tail)
      Creates an array of literals.

    • row

      public static ApiExpression row(Object head, Object... tail)
      Creates a row of expressions.

    • map

      public static ApiExpression map(Object key, Object value, Object... tail)
      Creates a map of expressions. 
      
 table.select(
     map(
         "key1", 1,
         "key2", 2,
         "key3", 3
     ))

      Note keys and values should have the same types for all entries.

    • mapFromArrays

      public static ApiExpression mapFromArrays(Object key, Object value)
      Creates a map from an array of keys and an array of values. 
      
 table.select(
     mapFromArrays(
         array("key1", "key2", "key3"),
         array(1, 2, 3)
     ))

      Note both arrays should have the same length.

    • rowInterval

      public static ApiExpression rowInterval(Long rows)
      Creates an interval of rows.
      See Also:

    • pi

      public static ApiExpression pi()
      Returns a value that is closer than any other value to pi.

    • e

      public static ApiExpression e()
      Returns a value that is closer than any other value to e.

    • rand

      public static ApiExpression rand()
      Returns a pseudorandom double value between 0.0 (inclusive) and 1.0 (exclusive).

    • rand

      public static ApiExpression rand(Object seed)
      Returns a pseudorandom double value between 0.0 (inclusive) and 1.0 (exclusive) with a initial seed. Two rand() functions will return identical sequences of numbers if they have same initial seed.

    • randInteger

      public static ApiExpression randInteger(Object bound)
      Returns a pseudorandom integer value between 0 (inclusive) and the specified value (exclusive).

    • randInteger

      public static ApiExpression randInteger(Object seed, Object bound)
      Returns a pseudorandom integer value between 0 (inclusive) and the specified value (exclusive) with a initial seed. Two randInteger() functions will return identical sequences of numbers if they have same initial seed and same bound.

    • concat

      public static ApiExpression concat(Object string, Object... strings)
      Returns the string that results from concatenating the arguments. Returns NULL if any argument is NULL.

    • atan2

      public static ApiExpression atan2(Object y, Object x)
      Calculates the arc tangent of a given coordinate.

    • negative

      public static ApiExpression negative(Object v)
      Returns negative numeric.

    • concatWs

      public static ApiExpression concatWs(Object separator, Object string, Object... strings)
      Returns the string that results from concatenating the arguments and separator. Returns NULL If the separator is NULL.

      Note: this function does not skip empty strings. However, it does skip any NULL values after the separator argument.

    • uuid

      public static ApiExpression uuid()
      Returns an UUID (Universally Unique Identifier) string (e.g., "3d3c68f7-f608-473f-b60c-b0c44ad4cc4e") according to RFC 4122 type 4 (pseudo randomly generated) UUID. The UUID is generated using a cryptographically strong pseudo random number generator.

    • nullOf

      public static ApiExpression nullOf(org.apache.flink.table.types.DataType dataType)
      Returns a null literal value of a given data type.

      e.g. nullOf(DataTypes.INT())

    • nullOf

      public static ApiExpression nullOf(org.apache.flink.api.common.typeinfo.TypeInformation<?> typeInfo)
      Deprecated.
      This method will be removed in future versions as it uses the old type system. It is recommended to use nullOf(DataType) instead which uses the new type system based on DataTypes. Please make sure to use either the old or the new type system consistently to avoid unintended behavior. See the website documentation for more information.

    • log

      public static ApiExpression log(Object value)
      Calculates the logarithm of the given value.

    • log

      public static ApiExpression log(Object base, Object value)
      Calculates the logarithm of the given value to the given base.

    • sourceWatermark

      public static ApiExpression sourceWatermark()
      Source watermark declaration for Schema.

      This is a marker function that doesn't have concrete runtime implementation. It can only be used as a single expression in Schema.Builder.watermark(String, Expression). The declaration will be pushed down into a table source that implements the SupportsSourceWatermark interface. The source will emit system-defined watermarks afterwards.

      Please check the documentation whether the connector supports source watermarks.

    • ifThenElse

      public static ApiExpression ifThenElse(Object condition, Object ifTrue, Object ifFalse)
      Ternary conditional operator that decides which of two other expressions should be evaluated based on a evaluated boolean condition.

      e.g. ifThenElse($("f0") > 5, "A", "B") leads to "A"

      Parameters:
      condition - boolean condition
      ifTrue - expression to be evaluated if condition holds
      ifFalse - expression to be evaluated if condition does not hold

    • coalesce

      public static ApiExpression coalesce(Object... args)
      Returns the first argument that is not NULL.

      If all arguments are NULL, it returns NULL as well. The return type is the least restrictive, common type of all of its arguments. The return type is nullable if all arguments are nullable as well.

      Examples: 

      
 // Returns "default"
 coalesce(null, "default")
 // Returns the first non-null value among f0 and f1, or "default" if f0 and f1 are both null
 coalesce($("f0"), $("f1"), "default")
      Parameters:
      args - the input expressions.

    • withAllColumns

      public static ApiExpression withAllColumns()
      Creates an expression that selects all columns. It can be used wherever an array of expression is accepted such as function calls, projections, or groupings.

      This expression is a synonym of $("*"). It is semantically equal to SELECT * in SQL when used in a projection.

      Example: 

      
 tab.select(withAllColumns())
      See Also:

    • withColumns

      public static ApiExpression withColumns(Object head, Object... tail)
      Creates an expression that selects a range of columns. It can be used wherever an array of expression is accepted such as function calls, projections, or groupings.

      A range can either be index-based or name-based. Indices start at 1 and boundaries are inclusive.

      e.g. withColumns(range("b", "c")) or withColumns($("*"))

    • withoutColumns

      public static ApiExpression withoutColumns(Object head, Object... tail)
      Creates an expression that selects all columns except for the given range of columns. It can be used wherever an array of expression is accepted such as function calls, projections, or groupings.

      A range can either be index-based or name-based. Indices start at 1 and boundaries are inclusive.

      e.g. withoutColumns(range("b", "c")) or withoutColumns($("c"))

    • jsonObject

      public static ApiExpression jsonObject(org.apache.flink.table.api.JsonOnNull onNull, Object... keyValues)
      Builds a JSON object string from a list of key-value pairs.

      is an even-numbered list of alternating key/value pairs. Note that keys must be non-NULL string literals, while values may be arbitrary expressions.

      This function returns a JSON string. The onNull behavior defines how to treat NULL values.

      Values which are created from another JSON construction function call (jsonObject, jsonArray) are inserted directly rather than as a string. This allows building nested JSON structures.

      Examples: 

      
 // {}
 jsonObject(JsonOnNull.NULL)
 // "{\"K1\":\"V1\",\"K2\":\"V2\"}"
 // {"K1":"V1","K2":"V2"}
 jsonObject(JsonOnNull.NULL, "K1", "V1", "K2", "V2")

 // Expressions as values
 jsonObject(JsonOnNull.NULL, "orderNo", $("orderId"))

 // ON NULL
 jsonObject(JsonOnNull.NULL, "K1", nullOf(DataTypes.STRING()))   // "{\"K1\":null}"
 jsonObject(JsonOnNull.ABSENT, "K1", nullOf(DataTypes.STRING())) // "{}"

 // {"K1":{"K2":"V"}}
 jsonObject(JsonOnNull.NULL, "K1", jsonObject(JsonOnNull.NULL, "K2", "V"))
      See Also:

    • jsonObjectAgg

      public static ApiExpression jsonObjectAgg(org.apache.flink.table.api.JsonOnNull onNull, Object keyExpr, Object valueExpr)
      Builds a JSON object string by aggregating key-value expressions into a single JSON object.

      The key expression must return a non-nullable character string. Value expressions can be arbitrary, including other JSON functions. If a value is NULL, the onNull behavior defines what to do.

      Note that keys must be unique. If a key occurs multiple times, an error will be thrown.

      This function is currently not supported in OVER windows.

      Examples: 

      
 // "{\"Apple\":2,\"Banana\":17,\"Orange\":0}"
 orders.select(jsonObjectAgg(JsonOnNull.NULL, $("product"), $("cnt")))
      See Also:

    • jsonString

      public static ApiExpression jsonString(Object value)
      Serializes a value into JSON.

      This function returns a JSON string containing the serialized value. If the value is null, the function returns null.

      Examples: 

      
 // null
 jsonString(nullOf(DataTypes.INT()))

 jsonString(1)                   // "1"
 jsonString(true)                // "true"
 jsonString("Hello, World!")     // "\"Hello, World!\""
 jsonString(Arrays.asList(1, 2)) // "[1,2]"

    • jsonArray

      public static ApiExpression jsonArray(org.apache.flink.table.api.JsonOnNull onNull, Object... values)
      Builds a JSON array string from a list of values.

      This function returns a JSON string. The values can be arbitrary expressions. The onNull behavior defines how to treat NULL values.

      Elements which are created from another JSON construction function call ( jsonObject, jsonArray) are inserted directly rather than as a string. This allows building nested JSON structures.

      Examples: 

      
 // "[]"
 jsonArray(JsonOnNull.NULL)
 // "[1,\"2\"]"
 jsonArray(JsonOnNull.NULL, 1, "2")

 // Expressions as values
 jsonArray(JsonOnNull.NULL, $("orderId"))

 // ON NULL
 jsonArray(JsonOnNull.NULL, nullOf(DataTypes.STRING()))   // "[null]"
 jsonArray(JsonOnNull.ABSENT, nullOf(DataTypes.STRING())) // "[]"

 // "[[1]]"
 jsonArray(JsonOnNull.NULL, jsonArray(JsonOnNull.NULL, 1))
      See Also:

    • jsonArrayAgg

      public static ApiExpression jsonArrayAgg(org.apache.flink.table.api.JsonOnNull onNull, Object itemExpr)
      Builds a JSON object string by aggregating items into an array.

      Item expressions can be arbitrary, including other JSON functions. If a value is NULL, the onNull behavior defines what to do.

      This function is currently not supported in OVER windows, unbounded session windows, or hop windows.

      Examples: 

      
 // "[\"Apple\",\"Banana\",\"Orange\"]"
 orders.select(jsonArrayAgg(JsonOnNull.NULL, $("product")))
      See Also:

    • lead

      public static ApiExpression lead(Object value)
      A window function that provides access to a row that comes directly after the current row.

      Example: 

      
 table.window(Over.orderBy($("ts")).partitionBy("organisation").as("w"))
    .select(
       $("organisation"),
       $("revenue"),
       lag($("revenue")).over($("w").as("next_revenue")
    )

    • lead

      public static ApiExpression lead(Object value, Object offset)
      A window function that provides access to a row at a specified physical offset which comes after the current row.

      Example: 

      
 table.window(Over.orderBy($("ts")).partitionBy("organisation").as("w"))
    .select(
       $("organisation"),
       $("revenue"),
       lag($("revenue"), 1).over($("w").as("next_revenue")
    )

    • lead

      public static ApiExpression lead(Object value, Object offset, Object defaultValue)
      A window function that provides access to a row at a specified physical offset which comes after the current row.

      The value to return when offset is beyond the scope of the partition. If a default value is not specified, NULL is returned. default must be type-compatible with value.

      Example: 

      
 table.window(Over.orderBy($("ts")).partitionBy("organisation").as("w"))
    .select(
       $("organisation"),
       $("revenue"),
       lag($("revenue"), 1, lit(0)).over($("w").as("next_revenue")
    )

    • lag

      public static ApiExpression lag(Object value)
      A window function that provides access to a row that comes directly before the current row.

      Example: 

      
 table.window(Over.orderBy($("ts")).partitionBy("organisation").as("w"))
    .select(
       $("organisation"),
       $("revenue"),
       lag($("revenue")).over($("w").as("prev_revenue")
    )

    • lag

      public static ApiExpression lag(Object value, Object offset)
      A window function that provides access to a row at a specified physical offset which comes before the current row.

      Example: 

      
 table.window(Over.orderBy($("ts")).partitionBy("organisation").as("w"))
    .select(
       $("organisation"),
       $("revenue"),
       lag($("revenue"), 1).over($("w").as("prev_revenue")
    )

    • lag

      public static ApiExpression lag(Object value, Object offset, Object defaultValue)
      A window function that provides access to a row at a specified physical offset which comes before the current row.

      The value to return when offset is beyond the scope of the partition. If a default value is not specified, NULL is returned. default must be type-compatible with value.

      Example: 

      
 org.window(Over.orderBy($("ts")).partitionBy("organisation").as("w"))
    .select(
       $("organisation"),
       $("revenue"),
       lag($("revenue"), 1, lit(0)).over($("w").as("prev_revenue")
    )

    • call

      public static ApiExpression call(String path, Object... arguments)
      A call to a function that will be looked up in a catalog. There are two kinds of functions:
      • System functions - which are identified with one part names
      • Catalog functions - which are identified always with three parts names (catalog, database, function)

      Moreover each function can either be a temporary function or permanent one (which is stored in an external catalog).

      Based on that two properties the resolution order for looking up a function based on the provided functionName is following:

      • Temporary system function
      • System function
      • Temporary catalog function
      • Catalog function
      See Also:

    • call

      public static ApiExpression call(org.apache.flink.table.functions.UserDefinedFunction function, Object... arguments)
      A call to an unregistered, inline function.

      For functions that have been registered before and are identified by a name, use call(String, Object...).

    • call

      public static ApiExpression call(Class<? extends org.apache.flink.table.functions.UserDefinedFunction> function, Object... arguments)
      A call to an unregistered, inline function.

      For functions that have been registered before and are identified by a name, use call(String, Object...).

    • callSql

      public static ApiExpression callSql(String sqlExpression)
      A call to a SQL expression.

      The given string is parsed and translated into an Expression during planning. Only the translated expression is evaluated during runtime.

      Note: Currently, calls are limited to simple scalar expressions. Calls to aggregate or table-valued functions are not supported. Sub-queries are also not allowed.