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

Nested Class Summary

Nested classes/interfaces inherited from interface mondrian.spi.Dialect

Dialect.DatabaseProduct, Dialect.Datatype

Field Summary

Fields

Modifier and Type	Field and Description
static JdbcDialectFactory	FACTORY

Fields inherited from class mondrian.spi.impl.JdbcDialectImpl

databaseProduct, permitsSelectNotInGroupBy, productVersion

Constructor Summary

Constructors

Constructor and Description
ImpalaDialect(Connection connection) Creates an ImpalaDialect.

Method Summary

Modifier and Type	Method and Description
boolean	allowsCompoundCountDistinct() Returns whether this Dialect allows multiple arguments to the COUNT(DISTINCT ...) aggregate function, for example SELECT COUNT(DISTINCT x, y) FROM t
boolean	allowsDdl() Returns whether this dialect supports common SQL Data Definition Language (DDL) statements such as CREATE TABLE and DROP INDEX.
boolean	allowsJoinOn() Returns whether this dialect supports "ANSI-style JOIN syntax", FROM leftTable JOIN rightTable ON conditon.
boolean	allowsMultipleCountDistinct() Returns whether this Dialect supports more than one distinct aggregation in the same query.
boolean	allowsRegularExpressionInWhereClause() Informs Mondrian if the dialect supports regular expressions when creating the 'where' or the 'having' clause.
boolean	allowsSelectNotInGroupBy() Returns whether the database currently permits queries to include in the SELECT clause expressions that are not listed in the GROUP BY clause.
protected String	deduceIdentifierQuoteString(DatabaseMetaData databaseMetaData)
String	generateInline(List<String> columnNames, List<String> columnTypes, List<String[]> valueList) Generates a SQL statement to represent an inline dataset.
protected String	generateOrderByNulls(String expr, boolean ascending, boolean collateNullsLast) Generates SQL to force null values to collate last.
String	generateOrderItem(String expr, boolean nullable, boolean ascending, boolean collateNullsLast) 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.
String	generateRegularExpression(String source, String javaRegex) Must generate a String representing a regular expression match operation between a string literal and a Java regular expression.
Dialect.DatabaseProduct	getDatabaseProduct() Returns the database for this Dialect, or Dialect.DatabaseProduct.UNKNOWN if the database is not a common database.
void	quoteStringLiteral(StringBuilder buf, String value) Appends to a buffer a single-quoted SQL string.
boolean	requiresAliasForFromQuery() Returns whether this Dialect requires subqueries in the FROM clause to have an alias.
boolean	requiresOrderByAlias() 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.
boolean	supportsGroupByExpressions() Returns whether this Dialect supports expressions in the GROUP BY clause.

Methods inherited from class mondrian.spi.impl.HiveDialect

allowsAs, allowsOrderByAlias, deduceMaxColumnNameLength, deduceReadOnly, deduceSupportedResultSetStyles, quoteDateLiteral, quoteTimestampLiteral, requiresGroupByAlias, requiresUnionOrderByExprToBeInSelectClause, requiresUnionOrderByOrdinal

Methods inherited from class mondrian.spi.impl.JdbcDialectImpl

allowsCountDistinct, allowsCountDistinctWithOtherAggs, allowsDialectSharing, allowsFromQuery, allowsMultipleDistinctSqlMeasures, appendHintsAfterFromClause, caseWhenElse, computeStatisticsProviders, deduceProductName, deduceProductVersion, deduceSupportsSelectNotInGroupBy, extractEmbeddedFlags, generateCountExpression, generateInlineForAnsi, generateInlineGeneric, generateOrderByNullsAnsi, getMaxColumnNameLength, getProduct, getQuoteIdentifierString, getStatisticsProviders, getType, isDatabase, needsExponent, quote, quoteBooleanLiteral, quoteDateLiteral, quoteIdentifier, quoteIdentifier, quoteIdentifier, quoteIdentifier, quoteNumericLiteral, quoteTimeLiteral, quoteTimestampLiteral, requiresHavingAlias, supportsGroupingSets, supportsMultiValueInExpr, supportsResultSetConcurrency, supportsUnlimitedValueList, toString, toUpper

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

FACTORY

public static final JdbcDialectFactory FACTORY

Constructor Detail

ImpalaDialect

public ImpalaDialect(Connection connection)
              throws SQLException

Creates an ImpalaDialect.

Parameters:

connection - Connection

Throws:

SQLException - on error

Method Detail

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:

Dialect.allowsCountDistinct(), Dialect.allowsMultipleCountDistinct()

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:

Dialect.allowsFromQuery()

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:

DatabaseMetaData.isReadOnly()