Package mondrian.spi.impl

Class ImpalaDialect

java.lang.Object
mondrian.spi.impl.JdbcDialectImpl
mondrian.spi.impl.HiveDialect
mondrian.spi.impl.ImpalaDialect
All Implemented Interfaces:
Dialect
public class ImpalaDialect extends HiveDialect
Dialect for Cloudera's Impala DB.
Since:
2/11/13
Author:
cboyden

  • Field Details

  • Constructor Details

    • ImpalaDialect

      public ImpalaDialect(Connection connection) throws SQLException
      Creates an ImpalaDialect.
      Parameters:
      connection - Connection
      Throws:
      SQLException - on error

  • Method Details

    • deduceIdentifierQuoteString

      protected String deduceIdentifierQuoteString(DatabaseMetaData databaseMetaData)
      Overrides:
      deduceIdentifierQuoteString in class HiveDialect

    • getDatabaseProduct

      public Dialect.DatabaseProduct getDatabaseProduct()
      Description copied from interface: Dialect
      Returns the database for this Dialect, or Dialect.DatabaseProduct.UNKNOWN if the database is not a common database.
      Specified by:
      getDatabaseProduct in interface Dialect
      Overrides:
      getDatabaseProduct in class JdbcDialectImpl
      Returns:
      Database

    • generateOrderByNulls

      protected String generateOrderByNulls(String expr, boolean ascending, boolean collateNullsLast)
      Description copied from class: JdbcDialectImpl
      Generates SQL to force null values to collate last.

      This default implementation makes use of the ANSI SQL 1999 CASE-WHEN-THEN-ELSE in conjunction with IS NULL syntax. The resulting SQL will look something like this:

      CASE WHEN "expr" IS NULL THEN 0 ELSE 1 END

      You can override this method for a particular database to use something more efficient, like ISNULL().

      ANSI SQL provides the syntax "ASC/DESC NULLS LAST" and "ASC/DESC NULLS FIRST". If your database supports the ANSI syntax, implement this method by calling JdbcDialectImpl.generateOrderByNullsAnsi(java.lang.String, boolean, boolean).

      This method is only called from JdbcDialectImpl.generateOrderItem(String, boolean, boolean, boolean). Some dialects override that method and therefore never call this method.

      Overrides:
      generateOrderByNulls in class HiveDialect
      Parameters:
      expr - Expression.
      ascending - Whether ascending.
      collateNullsLast - Whether nulls should appear first or last.
      Returns:
      Expression to force null values to collate last or first.

    • generateOrderItem

      public String generateOrderItem(String expr, boolean nullable, boolean ascending, boolean collateNullsLast)
      Description copied from interface: Dialect
      Generates an item for an ORDER BY clause, sorting in the required direction, and ensuring that NULL values collate either before or after all non-NULL values, depending on the collateNullsLast parameter.
      Specified by:
      generateOrderItem in interface Dialect
      Overrides:
      generateOrderItem in class JdbcDialectImpl
      Parameters:
      expr - Expression
      nullable - Whether expression may have NULL values
      ascending - Whether to sort expression ascending
      collateNullsLast - Whether the null values should be sorted first or last.
      Returns:
      Expression modified so that NULL values collate last

    • allowsMultipleCountDistinct

      public boolean allowsMultipleCountDistinct()
      Description copied from interface: Dialect
      Returns whether this Dialect supports more than one distinct aggregation in the same query.

      In Derby 10.1,

      select couunt(distinct x) from t
      is OK, but
      select couunt(distinct x), count(distinct y) from t
      gives "Multiple DISTINCT aggregates are not supported at this time."
      Specified by:
      allowsMultipleCountDistinct in interface Dialect
      Overrides:
      allowsMultipleCountDistinct in class JdbcDialectImpl
      Returns:
      whether this Dialect supports more than one distinct aggregation in the same query

    • allowsCompoundCountDistinct

      public boolean allowsCompoundCountDistinct()
      Description copied from interface: Dialect
      Returns whether this Dialect allows multiple arguments to the COUNT(DISTINCT ...) aggregate function, for example
      SELECT COUNT(DISTINCT x, y) FROM t
      Specified by:
      allowsCompoundCountDistinct in interface Dialect
      Overrides:
      allowsCompoundCountDistinct in class HiveDialect
      Returns:
      whether Dialect allows multiple arguments to COUNT DISTINCT
      See Also:

    • requiresOrderByAlias

      public boolean requiresOrderByAlias()
      Description copied from interface: Dialect
      Returns true if this Dialect can include expressions in the ORDER BY clause only by adding an expression to the SELECT clause and using its alias.

      For example, in such a dialect,

      SELECT x FROM t ORDER BY x + y
      would be illegal, but
      SELECT x, x + y AS z FROM t ORDER BY z
      would be legal.

      MySQL, DB2 and Ingres are examples of such dialects.

      Specified by:
      requiresOrderByAlias in interface Dialect
      Overrides:
      requiresOrderByAlias in class HiveDialect
      Returns:
      Whether this Dialect can include expressions in the ORDER BY clause only by adding an expression to the SELECT clause and using its alias

    • requiresAliasForFromQuery

      public boolean requiresAliasForFromQuery()
      Description copied from interface: Dialect
      Returns whether this Dialect requires subqueries in the FROM clause to have an alias.
      Specified by:
      requiresAliasForFromQuery in interface Dialect
      Overrides:
      requiresAliasForFromQuery in class HiveDialect
      Returns:
      whether dialewct requires subqueries to have an alias
      See Also:

    • supportsGroupByExpressions

      public boolean supportsGroupByExpressions()
      Description copied from interface: Dialect
      Returns whether this Dialect supports expressions in the GROUP BY clause. Derby/Cloudscape and Infobright do not.
      Specified by:
      supportsGroupByExpressions in interface Dialect
      Overrides:
      supportsGroupByExpressions in class JdbcDialectImpl
      Returns:
      Whether this Dialect allows expressions in the GROUP BY clause

    • allowsSelectNotInGroupBy

      public boolean allowsSelectNotInGroupBy()
      Description copied from interface: Dialect
      Returns whether the database currently permits queries to include in the SELECT clause expressions that are not listed in the GROUP BY clause. The SQL standard allows this if the database can deduce that the expression is functionally dependent on columns in the GROUP BY clause.

      For example, SELECT empno, first_name || ' ' || last_name FROM emps GROUP BY empno is valid because empno is the primary key of the emps table, and therefore all columns are dependent on it. For a given value of empno, first_name || ' ' || last_name has a unique value.

      Most databases do not, MySQL is an example of one that does (if the functioality is enabled).

      Specified by:
      allowsSelectNotInGroupBy in interface Dialect
      Overrides:
      allowsSelectNotInGroupBy in class JdbcDialectImpl
      Returns:
      Whether this Dialect allows SELECT clauses to contain columns that are not in the GROUP BY clause

    • generateInline

      public String generateInline(List<String> columnNames, List<String> columnTypes, List<String[]> valueList)
      Description copied from interface: Dialect
      Generates a SQL statement to represent an inline dataset.

      For example, for Oracle, generates 

       SELECT 1 AS FOO, 'a' AS BAR FROM dual
 UNION ALL
 SELECT 2 AS FOO, 'b' AS BAR FROM dual

      For ANSI SQL, generates: 

       VALUES (1, 'a'), (2, 'b')
      Specified by:
      generateInline in interface Dialect
      Overrides:
      generateInline in class HiveDialect
      Parameters:
      columnNames - List of column names
      columnTypes - List of column types ("String" or "Numeric")
      valueList - List of rows values
      Returns:
      SQL string

    • allowsJoinOn

      public boolean allowsJoinOn()
      Description copied from interface: Dialect
      Returns whether this dialect supports "ANSI-style JOIN syntax", FROM leftTable JOIN rightTable ON conditon.
      Specified by:
      allowsJoinOn in interface Dialect
      Overrides:
      allowsJoinOn in class HiveDialect
      Returns:
      Whether this dialect supports FROM-JOIN-ON syntax.

    • quoteStringLiteral

      public void quoteStringLiteral(StringBuilder buf, String value)
      Description copied from interface: Dialect
      Appends to a buffer a single-quoted SQL string.

      For example, in the default dialect, quoteStringLiteral(buf, "Can't") appends "'Can''t'" to buf.

      Specified by:
      quoteStringLiteral in interface Dialect
      Overrides:
      quoteStringLiteral in class JdbcDialectImpl
      Parameters:
      buf - Buffer to append to
      value - Literal

    • allowsRegularExpressionInWhereClause

      public boolean allowsRegularExpressionInWhereClause()
      Description copied from interface: Dialect
      Informs Mondrian if the dialect supports regular expressions when creating the 'where' or the 'having' clause.
      Specified by:
      allowsRegularExpressionInWhereClause in interface Dialect
      Overrides:
      allowsRegularExpressionInWhereClause in class JdbcDialectImpl
      Returns:
      True if regular expressions are supported.

    • generateRegularExpression

      public String generateRegularExpression(String source, String javaRegex)
      Description copied from interface: Dialect
      Must generate a String representing a regular expression match operation between a string literal and a Java regular expression. The string literal might be a column identifier or some other identifier, but the implementation must presume that it is already escaped and fit for use. The regular expression is not escaped and must be adapted to the proper dialect rules.

      Postgres / Greenplum example:

      generateRegularExpression( "'foodmart'.'customer_name'", "(?i).*oo.*") -> 'foodmart'.'customer_name' ~ "(?i).*oo.*"

      Oracle example:

      generateRegularExpression( "'foodmart'.'customer_name'", ".*oo.*") -> REGEXP_LIKE('foodmart'.'customer_name', ".*oo.*")

      Dialects are allowed to return null if the dialect cannot convert that particular regular expression into something that the database would support.

      Specified by:
      generateRegularExpression in interface Dialect
      Overrides:
      generateRegularExpression in class JdbcDialectImpl
      Parameters:
      source - A String identifying the column to match against.
      javaRegex - A Java regular expression to match against.
      Returns:
      A dialect specific matching operation, or null if the dialect cannot convert that particular regular expression into something that the database would support.

    • allowsDdl

      public boolean allowsDdl()
      Description copied from interface: Dialect
      Returns whether this dialect supports common SQL Data Definition Language (DDL) statements such as CREATE TABLE and DROP INDEX.

      Access seems to allow DDL iff the .mdb file is writeable.

      Specified by:
      allowsDdl in interface Dialect
      Overrides:
      allowsDdl in class JdbcDialectImpl
      Returns:
      whether this Dialect supports DDL
      See Also: