DBIx::MyParsePP::Rule

DBIx::MyParsePP::RuleUser Contributed Perl DocumentatDBIx::MyParsePP::Rule(3)



NAME
       DBIx::MyParsePP::Rule - Access individual elements from the
       DBIx::MyParsePP parse tree

SYNOPSIS
	       use DBIx::MyParsePP;
	       use DBIx::MyParsePP::Rule;

	       my $parser = DBIx::MyParsePP->new();

	       my $query = $parser->parse("SELECT 1"); # $query is a DBIx::MyParsePP::Rule object
	       my $root = $query->root();
	       print $root->name();		       # prints ’query’, the top-level grammar rule

	       my @children = $root->chilren();	       #
	       print $children[0]->name();	       # prints ’verb_clause’, the second-level rule

	       print ref($chilren[1]);		       # prints ’DBIx::MyParsePP::Token’
	       print $chilren[1]->type();	       # prints END_OF_INPUT

	       print [[[$root->chilren()]->[0]->chilren()]->[0]->chilren()]->[0]->name(); # Prints ’select’

DESCRIPTION
       DBIx::MyParsePP uses the "sql_yacc.yy" grammar from the MySQL source
       to parse SQL strings. A parse tree is produced which contains one
       branch for every rule encountered during parsing. This means that very
       deep trees can be produced where only certain branches are important.

METHODS
       "new($rule_name, @chilren)" constructs a new rule

       "name()" and "getName()" returns the name of the rule

       "chilren()" and "getChildren()" return (as array) the right-side items
       that were matched for that rule, e.g.  its "child branches" in the
       parse tree.

       "toString()" converts the parse tree back into SQL by walking the tree
       and gathering all tokens in sequence.

EXTRACTING PARTS
       "extract(@names)" can be used to walk the tree and extract relevant
       parts. The method returns undef if no part of the tree matched, a
       DBIx::MyParse::Rule or a DBIx::MyParse::Token object if a sigle match
       was made, or a reference to an array of such objects if several parts
       matched. Names to the front of the @names list are matched first.

       "getFields()" or "fields()" can be used to obtain all fields refer-
       enced in a parse tree or a part of it. Those functions will return
       <undef> if no fields were referenced or a reference to an array con-
       taining "Rule" objects for each field.  The Rule object can contain
       several ’ident’ subrules if a database and/or a table name was speci-
       fied for the given field.

       "getTables()" or "tables()" can be used in the same manner to obtain
       all tables referenced in the parse tree.

SHRINKING THE TREE
       The raw tree produced by DBIx::MyParsePP contains too many branches,
       many of them not containing any useful information.  The
       "shrink($flags)" method is used to convert the tree into a more man-
       ageable form. $flags can contain the following constants joined by
       "│":

       "MYPARSEPP_SHRINK_IDENTICAL" if a parent and a child node are of the
       same type, they will be merged together. This way expressions such as
       "1 + 1 + 1" or "col1, col2, col3" will be converted from a nested tree
       with one item per branch into a single Rule containing a list of all
       the items and the tokens between them (e.g. "+" or ","). Expressions
       such as "1 + 2 * 3" will remain as a tree because multiplication and
       addition have different precedence.

       "MYPARSEPP_SHRINK_LEAFS" will remove any Rules that have no children.

       "MYPARSEPP_SHRINK_SINGLES" will remove any Rules that have just a sin-
       gle child, linking the child directly to the upper-level Rule.

       "MYPARSEPP_SHRINK_CHILDREN" will apply "schrink()" recursively for all
       children.

       If no flags are specified, all listed transformations are applied
       recursively.



perl v5.8.8			  2007-08-17	     DBIx::MyParsePP::Rule(3)