Class: DBI::BaseStatement

Inherits:
Base
  • Object
show all
Defined in:
lib/dbi/base_classes/statement.rb

Overview

StatementHandles are used to encapsulate the process of managing a statement (DDL or DML) and its parameters, sending it to the database, and gathering any results from the execution of that statement.

As with the other ‘Base` classes, the terms “DBD Required” and “DBD Optional” are defined in DBI::BaseDatabase.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(attr = nil) ⇒ BaseStatement

Returns a new instance of BaseStatement.



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# File 'lib/dbi/base_classes/statement.rb', line 14

def initialize(attr=nil)
    @attr = attr || {}
end

Instance Attribute Details

#raise_error ⇒ Object

Returns the value of attribute raise_error.



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# File 'lib/dbi/base_classes/statement.rb', line 12

def raise_error
  @raise_error
end

Instance Method Details

#[](attr) ⇒ Object

Get statement attributes.



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# File 'lib/dbi/base_classes/statement.rb', line 159

def [](attr)
    @attr ||= { }
    @attr[attr]
end

#[]=(attr, value) ⇒ Object

Set statement attributes. DBD Optional.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 167

def []=(attr, value)
    raise NotSupportedError
end

#bind_param(param, value, attribs) ⇒ Object

Bind a parameter to the statement. DBD Required.

The parameter number is numeric and indexes starting at 1. This corresponds to the question marks (?) in the statement from the left-most part of the statement moving forward.

The value may be any ruby type. How these are handled is DBD-dependent, but the vast majority of DBDs will convert these to string inside the query.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 29

def bind_param(param, value, attribs)
    raise NotImplementedError
end

#bind_params(*bindvars) ⇒ Object

Take a list of bind variables and bind them successively using bind_param.



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# File 'lib/dbi/base_classes/statement.rb', line 74

def bind_params(*bindvars)
    bindvars.each_with_index {|val,i| bind_param(i+1, val, nil) }
    self
end

#cancel ⇒ Object

Cancel any result cursors. DBD Optional, but intentionally does not raise any exception as it’s used internally to maintain consistency.



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# File 'lib/dbi/base_classes/statement.rb', line 83

def cancel
end

#column_info ⇒ Object

returns result-set column information as array of hashs, where each hash represents one column. See BaseDatabase#columns. DBD Required.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 63

def column_info
    raise NotImplementedError
end

#execute ⇒ Object

Execute the statement with the known binds. DBD Required.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 36

def execute
    raise NotImplementedError
end

#fetch ⇒ Object

Fetch the next row in the result set. DBD Required.

DBI::Row is responsible for formatting the data the DBD provides it.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 54

def fetch
    raise NotImplementedError
end

#fetch_all ⇒ Object

Fetch all available rows. Result is Array of DBI::Row.



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# File 'lib/dbi/base_classes/statement.rb', line 141

def fetch_all
    rows = []
    loop do
        row = fetch
        break if row.nil?
        rows << row.dup
    end

    if rows.empty?
        nil
    else
        rows
    end
end

#fetch_many(cnt) ⇒ Object

fetch x rows. The result is Array of DBI::Row.



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# File 'lib/dbi/base_classes/statement.rb', line 123

def fetch_many(cnt)
    rows = []
    cnt.times do
        row = fetch
        break if row.nil?
        rows << row.dup
    end

    if rows.empty?
        nil
    else
        rows
    end
end

#fetch_scroll(direction, offset) ⇒ Object

fetch_scroll is provided with a direction and offset and works similar to how seek() is used on files.

The constants available for direction are as follows:

  • SQL_FETCH_NEXT: fetch the next result.

  • SQL_FETCH_LAST: fetch the last result, period.

  • SQL_FETCH_RELATIVE: fetch the result at the offset.

Other constants can be used, but if this method is not supplied by the driver, they will result in a raise of DBI::NotSupportedError.



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# File 'lib/dbi/base_classes/statement.rb', line 100

def fetch_scroll(direction, offset)
    case direction
    when SQL_FETCH_NEXT
        return fetch
    when SQL_FETCH_LAST
        last_row = nil
        while (row=fetch) != nil
            last_row = row
        end
        return last_row
    when SQL_FETCH_RELATIVE
        raise NotSupportedError if offset <= 0
        row = nil
        offset.times { row = fetch; break if row.nil? }
        return row
    else
        raise NotSupportedError
    end
end

#finish ⇒ Object

Close the statement and any result cursors. DBD Required.

Note

Most implementations will fail miserably if you forget to finish your statement handles.

Raises:



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# File 'lib/dbi/base_classes/statement.rb', line 45

def finish
    raise NotImplementedError
end