public class ImpalaDialect extends HiveDialect
Dialect.DatabaseProduct, Dialect.Datatype| Modifier and Type | Field and Description |
|---|---|
static JdbcDialectFactory |
FACTORY |
databaseProduct, permitsSelectNotInGroupBy, productVersion| Constructor and Description |
|---|
ImpalaDialect(Connection connection)
Creates an ImpalaDialect.
|
| Modifier and Type | Method and Description |
|---|---|
boolean |
allowsCompoundCountDistinct()
Returns whether this Dialect allows multiple arguments to the
COUNT(DISTINCT ...) aggregate function, for example
|
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.
|
allowsAs, deduceMaxColumnNameLength, deduceReadOnly, deduceSupportedResultSetStyles, quoteDateLiteral, requiresUnionOrderByExprToBeInSelectClauseallowsCountDistinct, allowsDialectSharing, allowsFromQuery, allowsMultipleDistinctSqlMeasures, allowsOrderByAlias, appendHintsAfterFromClause, caseWhenElse, computeStatisticsProviders, deduceProductName, deduceProductVersion, deduceSupportsSelectNotInGroupBy, generateCountExpression, generateInlineForAnsi, generateInlineGeneric, generateOrderByNullsAnsi, getMaxColumnNameLength, getProduct, getQuoteIdentifierString, getStatisticsProviders, getType, isDatabase, logTypeInfo, needsExponent, quote, quoteBooleanLiteral, quoteDateLiteral, quoteIdentifier, quoteIdentifier, quoteIdentifier, quoteIdentifier, quoteNumericLiteral, quoteTimeLiteral, quoteTimestampLiteral, requiresGroupByAlias, requiresHavingAlias, requiresUnionOrderByOrdinal, supportsGroupingSets, supportsMultiValueInExpr, supportsResultSetConcurrency, supportsUnlimitedValueList, toString, toUpperpublic static final JdbcDialectFactory FACTORY
public ImpalaDialect(Connection connection) throws SQLException
connection - ConnectionSQLException - on errorprotected String deduceIdentifierQuoteString(DatabaseMetaData databaseMetaData)
deduceIdentifierQuoteString in class HiveDialectpublic Dialect.DatabaseProduct getDatabaseProduct()
DialectDialect.DatabaseProduct.UNKNOWN if the database is
not a common database.getDatabaseProduct in interface DialectgetDatabaseProduct in class JdbcDialectImplprotected String generateOrderByNulls(String expr, boolean ascending, boolean collateNullsLast)
JdbcDialectImplThis 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.
generateOrderByNulls in class HiveDialectexpr - Expression.ascending - Whether ascending.collateNullsLast - Whether nulls should appear first or last.public String generateOrderItem(String expr, boolean nullable, boolean ascending, boolean collateNullsLast)
DialectcollateNullsLast
parameter.generateOrderItem in interface DialectgenerateOrderItem in class JdbcDialectImplexpr - Expressionnullable - Whether expression may have NULL valuesascending - Whether to sort expression ascendingcollateNullsLast - Whether the null values should be sorted first
or last.public boolean allowsMultipleCountDistinct()
DialectIn 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."allowsMultipleCountDistinct in interface DialectallowsMultipleCountDistinct in class JdbcDialectImplpublic boolean allowsCompoundCountDistinct()
DialectCOUNT(DISTINCT ...) aggregate function, for example
SELECT COUNT(DISTINCT x, y) FROM t
allowsCompoundCountDistinct in interface DialectallowsCompoundCountDistinct in class HiveDialectDialect.allowsCountDistinct(),
Dialect.allowsMultipleCountDistinct()public boolean requiresOrderByAlias()
DialectFor 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.
requiresOrderByAlias in interface DialectrequiresOrderByAlias in class HiveDialectpublic boolean requiresAliasForFromQuery()
DialectrequiresAliasForFromQuery in interface DialectrequiresAliasForFromQuery in class HiveDialectDialect.allowsFromQuery()public boolean supportsGroupByExpressions()
DialectsupportsGroupByExpressions in interface DialectsupportsGroupByExpressions in class JdbcDialectImplpublic boolean allowsSelectNotInGroupBy()
DialectFor 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).
allowsSelectNotInGroupBy in interface DialectallowsSelectNotInGroupBy in class JdbcDialectImplpublic String generateInline(List<String> columnNames, List<String> columnTypes, List<String[]> valueList)
DialectFor 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')
generateInline in interface DialectgenerateInline in class HiveDialectcolumnNames - List of column namescolumnTypes - List of column types ("String" or "Numeric")valueList - List of rows valuespublic boolean allowsJoinOn()
DialectFROM leftTable JOIN rightTable ON conditon.allowsJoinOn in interface DialectallowsJoinOn in class HiveDialectpublic void quoteStringLiteral(StringBuilder buf, String value)
DialectFor example, in the default dialect,
quoteStringLiteral(buf, "Can't") appends
"'Can''t'" to buf.
quoteStringLiteral in interface DialectquoteStringLiteral in class JdbcDialectImplbuf - Buffer to append tovalue - Literalpublic boolean allowsRegularExpressionInWhereClause()
DialectallowsRegularExpressionInWhereClause in interface DialectallowsRegularExpressionInWhereClause in class JdbcDialectImplpublic String generateRegularExpression(String source, String javaRegex)
DialectPostgres / 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.
generateRegularExpression in interface DialectgenerateRegularExpression in class JdbcDialectImplsource - A String identifying the column to match against.javaRegex - A Java regular expression to match against.public boolean allowsDdl()
DialectCREATE TABLE and
DROP INDEX.
Access seems to allow DDL iff the .mdb file is writeable.
allowsDdl in interface DialectallowsDdl in class JdbcDialectImplDatabaseMetaData.isReadOnly()