Class: DBI::StatementHandle

Inherits:
Handle
  • Object
show all
Includes:
Enumerable
Defined in:
lib/dbi/handles/statement.rb

Overview

StatementHandle is the interface the consumer sees after successfully issuing a DatabaseHandle#prepare. They may also be exposed through other methods that send statements to the database.

Almost all methods in this class will raise InterfaceError if the statement is already finished.

Instance Attribute Summary collapse

Attributes inherited from Handle

#convert_types, #handle, #trace_mode, #trace_output

Instance Method Summary collapse

Methods inherited from Handle

#func, #trace

Constructor Details

#initialize(handle, fetchable = false, prepared = true, convert_types = true, executed = false) ⇒ StatementHandle



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# File 'lib/dbi/handles/statement.rb', line 17

def initialize(handle, fetchable=false, prepared=true, convert_types=true, executed=false)
    super(handle)
    @fetchable = fetchable
    @prepared  = prepared     # only false if immediate execute was used
    @executed  = executed     # only true if the statement was already executed.
    @cols = nil
    @coltypes = nil
    @convert_types = convert_types

    if @fetchable
        @row = DBI::Row.new(column_names, column_types, nil, @convert_types)
    else
        @row = nil
    end
end

Instance Attribute Details

#dbhObject

Returns the value of attribute dbh



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

def dbh
  @dbh
end

#raise_errorObject

Returns the value of attribute raise_error



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# File 'lib/dbi/handles/statement.rb', line 15

def raise_error
  @raise_error
end

Instance Method Details

#[](attr) ⇒ Object

Get an attribute from the StatementHandle object.



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# File 'lib/dbi/handles/statement.rb', line 358

def [] (attr)
    sanity_check
    @handle[attr]
end

#[]=(attr, val) ⇒ Object

Set an attribute on the StatementHandle object.



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# File 'lib/dbi/handles/statement.rb', line 364

def []= (attr, val)
    sanity_check
    @handle[attr] = val
end

#bind_coltype(pos, type) ⇒ Object

Instruct successive calls to #fetch to cast the type returned into `type`, for row position `pos`. Like all bind_* calls, `pos` indexes starting at 1.

`type` is an object with the DBI::Type calling convention.

This call must be called after #execute has successfully ran, otherwise it will raise InterfaceError.

Example:

# `foo` is an integer and this statement will return two rows. 
sth = dbh.prepare("select foo from bar") 
# would raise InterfaceError if called here
sth.execute

sth.bind_coltype(1, DBI::Type::Varchar) 
# would normally use DBI::Type::Integer and return a Fixnum. We'll make it a string.
sth.fetch => ["1"]

# Here we coerce it to Float.
sth.bind_coltype(1, DBI::Type::Float)
sth.fetch => [1.0]
sth.finish


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# File 'lib/dbi/handles/statement.rb', line 72

def bind_coltype(pos, type)
    sanity_check({:prepared => true, :executed => true})
    
    coltypes = column_types

    if (pos - 1) < 0
        raise InterfaceError, "bind positions index starting at 1"
    end

    coltypes[pos-1] = type
    @row = DBI::Row.new(column_names, coltypes, nil, @convert_types)
end

#bind_param(param, value, attribs = nil) ⇒ Object

Just like BaseStatement#bind_param, but will attempt to convert the type if it's supposed to, adhering to the DBD's current ruleset.



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# File 'lib/dbi/handles/statement.rb', line 89

def bind_param(param, value, attribs=nil)
    sanity_check({ :prepared => true })

    if @convert_types
        value = DBI::Utils::ConvParam.conv_param(dbh.driver_name, value)[0]
    end

    @handle.bind_param(param, value, attribs)
end

#cancelObject

Cancel the query, closing any open result cursors and truncating any result sets.

The difference between this and #finish is that cancelled statements may be re-executed.



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# File 'lib/dbi/handles/statement.rb', line 146

def cancel
    sanity_check
    @handle.cancel if @fetchable
    @fetchable = false
end

#column_infoObject

See BaseStatement#column_info.



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# File 'lib/dbi/handles/statement.rb', line 183

def column_info
    sanity_check
    @handle.column_info.collect {|col| ColumnInfo.new(col) }
end

#column_namesObject

Obtains the column names for this query as an array.



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# File 'lib/dbi/handles/statement.rb', line 155

def column_names
    sanity_check
    return @cols unless @cols.nil?
    @cols = @handle.column_info.collect {|col| col['name'] }
end

#column_typesObject

Obtain the type mappings for the columns in this query based on ColumnInfo data on the query.

The result will be a position-dependent array of objects that conform to the DBI::Type calling syntax.



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# File 'lib/dbi/handles/statement.rb', line 168

def column_types
    sanity_check
    return @coltypes unless @coltypes.nil?
    @coltypes = @handle.column_info.collect do |col| 
        if col['dbi_type']
            col['dbi_type']
        else
            DBI::TypeUtil.type_name_to_module(col['type_name'])
        end
    end
end

#each(&p) ⇒ Object

Synonym for #fetch with a block.

Raises:



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# File 'lib/dbi/handles/statement.rb', line 236

def each(&p)
    sanity_check({:fetchable => true, :prepared => true, :executed => true})
    raise InterfaceError, "No block given" unless block_given?

    fetch(&p)
end

#execute(*bindvars) ⇒ Object

Execute the statement.

This generally means that the statement will be sent to the database and some form of result cursor will be obtained, but is ultimately driver-dependent.

If arguments are supplied, these are fed to #bind_param.



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# File 'lib/dbi/handles/statement.rb', line 107

def execute(*bindvars)
    cancel     # cancel before 
    sanity_check({:prepared => true })

    if @convert_types
        bindvars = DBI::Utils::ConvParam.conv_param(dbh.driver_name, *bindvars)
    end

    @handle.bind_params(*bindvars)
    @handle.execute
    @fetchable = true
    @executed = true

    # TODO:?
    #if @row.nil?
    @row = DBI::Row.new(column_names, column_types, nil, @convert_types)
    #end
    return nil
end

#fetch(&p) ⇒ Object

See BaseStatement#fetch.

fetch can also take a block which will be applied to each row in a similar fashion to Enumerable#collect. See #each.



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# File 'lib/dbi/handles/statement.rb', line 207

def fetch(&p)
    sanity_check({ :fetchable => true, :prepared => true, :executed => true })

    if block_given? 
        while (res = @handle.fetch) != nil
            @row = @row.dup
            @row.set_values(res)
            yield @row
        end
        @handle.cancel
        @fetchable = false
        return nil
    else
        res = @handle.fetch
        if res.nil?
            @handle.cancel
            @fetchable = false
        else
            @row = @row.dup
            @row.set_values(res)
            res = @row
        end
        return res
    end
end

#fetch_allObject

Fetch the entire result set. Result is array of DBI::Row.



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# File 'lib/dbi/handles/statement.rb', line 321

def fetch_all
    sanity_check({:fetchable => true, :prepared => true, :executed => true})

    cols = column_names
    fetched_rows = []

    begin
        while row = fetch do
            fetched_rows.push(row)
        end
    rescue Exception
    end

    @handle.cancel
    @fetchable = false

    return fetched_rows
end

#fetch_arrayObject

Similar to #fetch, but returns Array of Array instead of Array of DBI::Row objects (and therefore does not perform type mapping). This is basically a way to get the raw data from the DBD.



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# File 'lib/dbi/handles/statement.rb', line 248

def fetch_array
    sanity_check({:fetchable => true, :prepared => true, :executed => true})

    if block_given? 
        while (res = @handle.fetch) != nil
            yield res
        end
        @handle.cancel
        @fetchable = false
        return nil
    else
        res = @handle.fetch
        if res.nil?
            @handle.cancel
            @fetchable = false
        end
        return res
    end
end

#fetch_hashObject

Map the columns and results into an Array of Hash resultset.

No type conversion is performed here. Expect this to change in 0.6.0.



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# File 'lib/dbi/handles/statement.rb', line 273

def fetch_hash
    sanity_check({:fetchable => true, :prepared => true, :executed => true})

    cols = column_names

    if block_given? 
        while (row = @handle.fetch) != nil
            hash = {}
            row.each_with_index {|v,i| hash[cols[i]] = v} 
            yield hash
        end
        @handle.cancel
        @fetchable = false
        return nil
    else
        row = @handle.fetch
        if row.nil?
            @handle.cancel
            @fetchable = false
            return nil
        else
            hash = {}
            row.each_with_index {|v,i| hash[cols[i]] = v} 
            return hash
        end
    end
end

#fetch_many(cnt) ⇒ Object

Fetch `cnt` rows. Result is array of DBI::Row



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# File 'lib/dbi/handles/statement.rb', line 304

def fetch_many(cnt)
    sanity_check({:fetchable => true, :prepared => true, :executed => true})

    cols = column_names
    rows = @handle.fetch_many(cnt)
    if rows.nil? or rows.empty?
        @handle.cancel
        @fetchable = false
        return []
    else
        return rows.collect{|r| tmp = @row.dup; tmp.set_values(r); tmp }
    end
end

#fetch_scroll(direction, offset = 1) ⇒ Object

See BaseStatement#fetch_scroll.



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# File 'lib/dbi/handles/statement.rb', line 343

def fetch_scroll(direction, offset=1)
    sanity_check({:fetchable => true, :prepared => true, :executed => true})

    row = @handle.fetch_scroll(direction, offset)
    if row.nil?
        #@handle.cancel
        #@fetchable = false
        return nil
    else
        @row.set_values(row)
        return @row
    end
end

#fetchable?Boolean

Returns true if the statement is believed to return data upon #fetch.

The current reliability of this (and the concept in general) is suspect.



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# File 'lib/dbi/handles/statement.rb', line 43

def fetchable?
    @fetchable
end

#finishObject

Finish the statement, causing the database to release all assets related to it (any result cursors, normally).

StatementHandles that have already been finished will normally be inoperable and unavailable for further use.



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# File 'lib/dbi/handles/statement.rb', line 134

def finish
    sanity_check
    @handle.finish
    @handle = nil
end

#finished?Boolean

Returns true if the StatementHandle has had #finish called on it, explicitly or otherwise.



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# File 'lib/dbi/handles/statement.rb', line 35

def finished?
    @handle.nil?
end

#rowsObject

Should return the row modified count as the result of statement execution.

However, some low-level drivers do not supply this information or supply misleading information (> 0 rows for read-only select statements, f.e.)



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# File 'lib/dbi/handles/statement.rb', line 195

def rows
    sanity_check
    @handle.rows
end