ibis::fromClause Class Reference

A class to represent the from clause. More...

#include <fromClause.h>

Public Member Functions
const char *	alias (const char *) const
	Given a name find its alias. More...
void	clear ()
	Remove the current content.
bool	empty () const
	Is it empty? Returns true or false.
	fromClause (const char *cl=0)
	Parse a new string as a from clause.
	fromClause (const ibis::table::stringArray &)
	Parse a list of strings.
	fromClause (const fromClause &)
	Copy constructor. Deep copy.
const ibis::compRange *	getJoinCondition () const
	Report the join condition.
void	getNames (ibis::table::stringArray &) const
	Fill the array nms with the known names. More...
const char *	getString (void) const
	Return a pointer to the string form of the from clause.
const char *	operator* (void) const
	Dereferences to the string form of the from clause.
fromClause &	operator= (const fromClause &rhs)
	Assignment operator.
int	parse (const char *cl)
	Parse a new string. More...
size_t	position (const char *) const
void	print (std::ostream &) const
	Print the content. More...
const char *	realName (const char *) const
	Given an alias find its real name. More...
void	reorderNames (const char *, const char *)
	Reorder the table names. More...
uint32_t	size () const
	Returns the number of valid names.
void	swap (fromClause &rhs)
	Swap the content of two from clauses.

Protected Attributes
std::vector< std::string >	aliases_
	The aliases.
std::string	clause_
ibis::compRange *	jcond_
	The join condition. More...
ibis::fromLexer *	lexer
	!< String version of the from clause.
std::vector< std::string >	names_
	The names of data tables.
std::map< const char *, size_t, ibis::lessi >	ordered_
	The ordered version of the names.

Friends
class	ibis::fromParser
	!< A pointer for the parser.

Detailed Description

A class to represent the from clause.

It parses a string into a list of names, a list of aliases and a join expression if present.

The alias may optionally be preceded by the keyword "AS". For example, "FROM table_a as a" and "FROM table_a a" mean the same thing.

The join expression is in the from clause can be of the form

table_a JOIN table_b USING join_column

or

table_a JOIN table_b ON arithmetic_expression

Note that the first form is equivalent to

table_a JOIN table_b ON table_a.join_column = table_b.join_column

Warning

The current version of FastBit only supports join operating on two data tables.

Member Function Documentation

const char * ibis::fromClause::alias

(

const char *

al

)

const

Given a name find its alias.

The incoming argument will be returned if it is neither an alias nor an actual table name mentioned in the from clause.

Referenced by ibis::quaere::create().

void ibis::fromClause::getNames

(

ibis::table::stringArray &

nms

)

const

Fill the array nms with the known names.

It returns both actual table names and their aliases in alphabetic order.

References ibis::array_t< T >::clear(), ibis::array_t< T >::push_back(), and ibis::array_t< T >::reserve().

int ibis::fromClause::parse

(

const char *

cl

)

Parse a new string.

Clear the existing content. A minimal amount of sanity check is also performed.

References ibis::util::clear().

Referenced by fromClause().

void ibis::fromClause::print

(

std::ostream &

out

)

const

Print the content.

Write a string version of the from clause to the specified output stream.

const char * ibis::fromClause::realName

(

const char *

al

)

const

Given an alias find its real name.

The input string will be returned if it is neither an alias nor an actual table name mentioned in the from clause.

Referenced by ibis::quaere::create().

void ibis::fromClause::reorderNames	(	const char *	nm0,
		const char *	nm1
	)

Reorder the table names.

The name matching nm0 will be placed first, followed by the one matching nm1.

Referenced by ibis::quaere::create().

Member Data Documentation

ibis::compRange* ibis::fromClause::jcond_

protected

The join condition.

A join condition may be specified in the from clause with the key words ON and USING, where On is followed by an arithmetic expression and USING is followed by a column name. The parser will translate the column name following USING into an eqaulity condition for generate a proper ibis::compRange object. If this variable is a nil pointer, no join condition has been specified in the from clause.

Referenced by fromClause(), getJoinCondition(), and swap().

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The documentation for this class was generated from the following files:

• fromClause.h
• fromClause.cpp