Package org.apache.flink.table.api

Class 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 Detail

      • 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 Detail

      • Expressions

        public Expressions()

    • Method Detail

      • 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:
        withAllColumns()

      • 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.

      • 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().

      • 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)

      • localTimestamp

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

      • 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.

      • 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​(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.

      • 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.

      • 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.

      • 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​(DataType dataType)
        Returns a null literal value of a given data type.

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

      • nullOf

        public static ApiExpression nullOf​(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(Object, Object...), withoutColumns(Object, Object...)

      • 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​(JsonOnNull onNull,
                                       Object... keyValues)
        Builds a JSON object string from a list of key-value pairs.

        {@param keyValues} 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:
        jsonArray(JsonOnNull, Object...)

      • jsonObjectAgg

        public static ApiExpression jsonObjectAgg​(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:
        jsonObject(JsonOnNull, Object...), jsonArrayAgg(JsonOnNull, Object)

      • 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​(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:
        jsonObject(JsonOnNull, Object...)

      • jsonArrayAgg

        public static ApiExpression jsonArrayAgg​(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:
        jsonArray(JsonOnNull, Object...), jsonObjectAgg(JsonOnNull, Object, 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.