class PG::Result
The class to represent the query result tuples (rows). An instance of this class is created as the result of every query. You may need to invoke the clear method of the instance when finished with the result for better memory performance.
Example:
require 'pg' conn = PGconn.open(:dbname => 'test') res = conn.exec('SELECT 1 AS a, 2 AS b, NULL AS c') res.getvalue(0,0) # '1' res[0]['b'] # '2' res[0]['c'] # nil
Public Instance Methods
Returns tuple n as a hash.
static VALUE pgresult_aref(VALUE self, VALUE index) { t_pg_result *this = pgresult_get_this_safe(self); int tuple_num = NUM2INT(index); int field_num; int num_tuples = PQntuples(this->pgresult); VALUE tuple; if( this->nfields == -1 ) pgresult_init_fnames( self ); if ( tuple_num < 0 || tuple_num >= num_tuples ) rb_raise( rb_eIndexError, "Index %d is out of range", tuple_num ); /* We reuse the Hash of the previous output for larger row counts. * This is somewhat faster than populating an empty Hash object. */ tuple = NIL_P(this->tuple_hash) ? rb_hash_new() : this->tuple_hash; for ( field_num = 0; field_num < this->nfields; field_num++ ) { VALUE val = this->p_typemap->funcs.typecast_result_value(this->p_typemap, self, tuple_num, field_num); rb_hash_aset( tuple, this->fnames[field_num], val ); } /* Store a copy of the filled hash for use at the next row. */ if( num_tuples > 10 ) this->tuple_hash = rb_hash_dup(tuple); return tuple; }
Returns true
if the underlying C struct will be cleared
automatically by libpq. Elsewise the result is cleared by #clear or by the GC when it's no
longer in use.
VALUE pgresult_autoclear_p( VALUE self ) { t_pg_result *this = pgresult_get_this(self); return this->autoclear ? Qtrue : Qfalse; }
Raises appropriate exception if PG::Result is in a bad state.
VALUE pg_result_check( VALUE self ) { t_pg_result *this = pgresult_get_this(self); VALUE error, exception, klass; char * sqlstate; if(this->pgresult == NULL) { PGconn *conn = pg_get_pgconn(this->connection); error = rb_str_new2( PQerrorMessage(conn) ); } else { switch (PQresultStatus(this->pgresult)) { case PGRES_TUPLES_OK: case PGRES_COPY_OUT: case PGRES_COPY_IN: #ifdef HAVE_CONST_PGRES_COPY_BOTH case PGRES_COPY_BOTH: #endif #ifdef HAVE_CONST_PGRES_SINGLE_TUPLE case PGRES_SINGLE_TUPLE: #endif case PGRES_EMPTY_QUERY: case PGRES_COMMAND_OK: return self; case PGRES_BAD_RESPONSE: case PGRES_FATAL_ERROR: case PGRES_NONFATAL_ERROR: error = rb_str_new2( PQresultErrorMessage(this->pgresult) ); break; default: error = rb_str_new2( "internal error : unknown result status." ); } } PG_ENCODING_SET_NOCHECK( error, ENCODING_GET(self) ); sqlstate = PQresultErrorField( this->pgresult, PG_DIAG_SQLSTATE ); klass = lookup_error_class( sqlstate ); exception = rb_exc_new3( klass, error ); rb_iv_set( exception, "@connection", this->connection ); rb_iv_set( exception, "@result", this->pgresult ? self : Qnil ); rb_exc_raise( exception ); /* Not reached */ return self; }
Clears the PG::Result object as the result of the query.
If #autoclear? is true then the result is marked as cleared and the underlying C struct will be cleared automatically by libpq.
VALUE pg_result_clear(VALUE self) { t_pg_result *this = pgresult_get_this(self); if( !this->autoclear ) PQclear(pgresult_get(self)); this->pgresult = NULL; return Qnil; }
Returns true
if the backend result memory has been free'd.
VALUE pgresult_cleared_p( VALUE self ) { t_pg_result *this = pgresult_get_this(self); return this->pgresult ? Qfalse : Qtrue; }
Returns the status string of the last query command.
static VALUE pgresult_cmd_status(VALUE self) { VALUE ret = rb_tainted_str_new2(PQcmdStatus(pgresult_get(self))); PG_ENCODING_SET_NOCHECK(ret, ENCODING_GET(self)); return ret; }
Returns the number of tuples (rows) affected by the SQL command.
If the SQL command that generated the PG::Result was not one of:
-
INSERT
-
UPDATE
-
DELETE
-
MOVE
-
FETCH
or if no tuples were affected, 0
is returned.
static VALUE pgresult_cmd_tuples(VALUE self) { long n; n = strtol(PQcmdTuples(pgresult_get(self)),NULL, 10); return INT2NUM(n); }
Returns an Array of the values from the nth column of each tuple in the result.
static VALUE pgresult_column_values(VALUE self, VALUE index) { int col = NUM2INT( index ); return make_column_result_array( self, col ); }
Invokes block for each tuple in the result set.
static VALUE pgresult_each(VALUE self) { PGresult *result; int tuple_num; RETURN_SIZED_ENUMERATOR(self, 0, NULL, pgresult_ntuples_for_enum); result = pgresult_get(self); for(tuple_num = 0; tuple_num < PQntuples(result); tuple_num++) { rb_yield(pgresult_aref(self, INT2NUM(tuple_num))); } return self; }
Yields each row of the result. The row is a list of column values.
static VALUE pgresult_each_row(VALUE self) { t_pg_result *this; int row; int field; int num_rows; int num_fields; RETURN_SIZED_ENUMERATOR(self, 0, NULL, pgresult_ntuples_for_enum); this = pgresult_get_this_safe(self); num_rows = PQntuples(this->pgresult); num_fields = PQnfields(this->pgresult); for ( row = 0; row < num_rows; row++ ) { PG_VARIABLE_LENGTH_ARRAY(VALUE, row_values, num_fields, PG_MAX_COLUMNS) /* populate the row */ for ( field = 0; field < num_fields; field++ ) { row_values[field] = this->p_typemap->funcs.typecast_result_value(this->p_typemap, self, row, field); } rb_yield( rb_ary_new4( num_fields, row_values )); } return Qnil; }
Returns the individual field of an error.
fieldcode
is one of:
-
PG_DIAG_SEVERITY
-
PG_DIAG_SQLSTATE
-
PG_DIAG_MESSAGE_PRIMARY
-
PG_DIAG_MESSAGE_DETAIL
-
PG_DIAG_MESSAGE_HINT
-
PG_DIAG_STATEMENT_POSITION
-
PG_DIAG_INTERNAL_POSITION
-
PG_DIAG_INTERNAL_QUERY
-
PG_DIAG_CONTEXT
-
PG_DIAG_SOURCE_FILE
-
PG_DIAG_SOURCE_LINE
-
PG_DIAG_SOURCE_FUNCTION
An example:
begin conn.exec( "SELECT * FROM nonexistant_table" ) rescue PG::Error => err p [ err.result.error_field( PG::Result::PG_DIAG_SEVERITY ), err.result.error_field( PG::Result::PG_DIAG_SQLSTATE ), err.result.error_field( PG::Result::PG_DIAG_MESSAGE_PRIMARY ), err.result.error_field( PG::Result::PG_DIAG_MESSAGE_DETAIL ), err.result.error_field( PG::Result::PG_DIAG_MESSAGE_HINT ), err.result.error_field( PG::Result::PG_DIAG_STATEMENT_POSITION ), err.result.error_field( PG::Result::PG_DIAG_INTERNAL_POSITION ), err.result.error_field( PG::Result::PG_DIAG_INTERNAL_QUERY ), err.result.error_field( PG::Result::PG_DIAG_CONTEXT ), err.result.error_field( PG::Result::PG_DIAG_SOURCE_FILE ), err.result.error_field( PG::Result::PG_DIAG_SOURCE_LINE ), err.result.error_field( PG::Result::PG_DIAG_SOURCE_FUNCTION ), ] end
Outputs:
["ERROR", "42P01", "relation \"nonexistant_table\" does not exist", nil, nil, "15", nil, nil, nil, "path/to/parse_relation.c", "857", "parserOpenTable"]
static VALUE pgresult_error_field(VALUE self, VALUE field) { PGresult *result = pgresult_get( self ); int fieldcode = NUM2INT( field ); char * fieldstr = PQresultErrorField( result, fieldcode ); VALUE ret = Qnil; if ( fieldstr ) { ret = rb_tainted_str_new2( fieldstr ); PG_ENCODING_SET_NOCHECK( ret, ENCODING_GET(self )); } return ret; }
Returns the error message of the command as a string.
static VALUE pgresult_error_message(VALUE self) { VALUE ret = rb_tainted_str_new2(PQresultErrorMessage(pgresult_get(self))); PG_ENCODING_SET_NOCHECK(ret, ENCODING_GET(self)); return ret; }
Returns the format (0 for text, 1 for binary) of column column_number.
Raises ArgumentError if column_number is out of range.
static VALUE pgresult_fformat(VALUE self, VALUE column_number) { PGresult *result = pgresult_get(self); int fnumber = NUM2INT(column_number); if (fnumber < 0 || fnumber >= PQnfields(result)) { rb_raise(rb_eArgError, "Column number is out of range: %d", fnumber); } return INT2FIX(PQfformat(result, fnumber)); }
Returns an Array of the values from the given field of each tuple in the result.
static VALUE pgresult_field_values( VALUE self, VALUE field ) { PGresult *result = pgresult_get( self ); const char *fieldname = StringValueCStr( field ); int fnum = PQfnumber( result, fieldname ); if ( fnum < 0 ) rb_raise( rb_eIndexError, "no such field '%s' in result", fieldname ); return make_column_result_array( self, fnum ); }
Returns an array of Strings representing the names of the fields in the result.
static VALUE pgresult_fields(VALUE self) { t_pg_result *this = pgresult_get_this_safe(self); if( this->nfields == -1 ) pgresult_init_fnames( self ); return rb_ary_new4( this->nfields, this->fnames ); }
Returns the type modifier associated with column column_number. See the ftype method for an example of how to use this.
Raises an ArgumentError if column_number is out of range.
static VALUE pgresult_fmod(VALUE self, VALUE column_number) { PGresult *result = pgresult_get(self); int fnumber = NUM2INT(column_number); int modifier; if (fnumber < 0 || fnumber >= PQnfields(result)) { rb_raise(rb_eArgError, "Column number is out of range: %d", fnumber); } modifier = PQfmod(result,fnumber); return INT2NUM(modifier); }
Returns the name of the column corresponding to index.
static VALUE pgresult_fname(VALUE self, VALUE index) { VALUE fname; PGresult *result = pgresult_get(self); int i = NUM2INT(index); if (i < 0 || i >= PQnfields(result)) { rb_raise(rb_eArgError,"invalid field number %d", i); } fname = rb_tainted_str_new2(PQfname(result, i)); PG_ENCODING_SET_NOCHECK(fname, ENCODING_GET(self)); return rb_obj_freeze(fname); }
Returns the index of the field specified by the string name
.
The given name
is treated like an identifier in an SQL
command, that is, it is downcased unless double-quoted. For example, given
a query result generated from the SQL command:
result = conn.exec( %Q{SELECT 1 AS FOO, 2 AS "BAR"} )
we would have the results:
result.fname( 0 ) # => "foo" result.fname( 1 ) # => "BAR" result.fnumber( "FOO" ) # => 0 result.fnumber( "foo" ) # => 0 result.fnumber( "BAR" ) # => ArgumentError result.fnumber( %Q{"BAR"} ) # => 1
Raises an ArgumentError if the specified name
isn't one of
the field names; raises a TypeError if name
is not a String.
static VALUE pgresult_fnumber(VALUE self, VALUE name) { int n; Check_Type(name, T_STRING); n = PQfnumber(pgresult_get(self), StringValueCStr(name)); if (n == -1) { rb_raise(rb_eArgError,"Unknown field: %s", StringValueCStr(name)); } return INT2FIX(n); }
Returns the size of the field type in bytes. Returns -1
if
the field is variable sized.
res = conn.exec("SELECT myInt, myVarChar50 FROM foo") res.size(0) => 4 res.size(1) => -1
static VALUE pgresult_fsize(VALUE self, VALUE index) { PGresult *result; int i = NUM2INT(index); result = pgresult_get(self); if (i < 0 || i >= PQnfields(result)) { rb_raise(rb_eArgError,"invalid field number %d", i); } return INT2NUM(PQfsize(result, i)); }
Returns the Oid of the table from which the column column_number was fetched.
Raises ArgumentError if column_number is out of range or if the Oid is undefined for that column.
static VALUE pgresult_ftable(VALUE self, VALUE column_number) { Oid n ; int col_number = NUM2INT(column_number); PGresult *pgresult = pgresult_get(self); if( col_number < 0 || col_number >= PQnfields(pgresult)) rb_raise(rb_eArgError,"Invalid column index: %d", col_number); n = PQftable(pgresult, col_number); return UINT2NUM(n); }
Returns the column number (within its table) of the table from which the column column_number is made up.
Raises ArgumentError if column_number is out of range or if the column number from its table is undefined for that column.
static VALUE pgresult_ftablecol(VALUE self, VALUE column_number) { int col_number = NUM2INT(column_number); PGresult *pgresult = pgresult_get(self); int n; if( col_number < 0 || col_number >= PQnfields(pgresult)) rb_raise(rb_eArgError,"Invalid column index: %d", col_number); n = PQftablecol(pgresult, col_number); return INT2FIX(n); }
Returns the data type associated with column_number.
The integer returned is the internal OID
number (in
PostgreSQL) of the type. To get a human-readable value for the type, use
the returned OID and the field's fmod value with the format_type() SQL
function:
# Get the type of the second column of the result 'res' typename = conn. exec( "SELECT format_type($1,$2)", [res.ftype(1), res.fmod(1)] ). getvalue( 0, 0 )
Raises an ArgumentError if column_number is out of range.
static VALUE pgresult_ftype(VALUE self, VALUE index) { PGresult* result = pgresult_get(self); int i = NUM2INT(index); if (i < 0 || i >= PQnfields(result)) { rb_raise(rb_eArgError, "invalid field number %d", i); } return UINT2NUM(PQftype(result, i)); }
Returns true
if the specified value is nil
;
false
otherwise.
static VALUE pgresult_getisnull(VALUE self, VALUE tup_num, VALUE field_num) { PGresult *result; int i = NUM2INT(tup_num); int j = NUM2INT(field_num); result = pgresult_get(self); if (i < 0 || i >= PQntuples(result)) { rb_raise(rb_eArgError,"invalid tuple number %d", i); } if (j < 0 || j >= PQnfields(result)) { rb_raise(rb_eArgError,"invalid field number %d", j); } return PQgetisnull(result, i, j) ? Qtrue : Qfalse; }
Returns the (String) length of the field in bytes.
Equivalent to
res.value(tup_num,field_num).length
.
static VALUE pgresult_getlength(VALUE self, VALUE tup_num, VALUE field_num) { PGresult *result; int i = NUM2INT(tup_num); int j = NUM2INT(field_num); result = pgresult_get(self); if (i < 0 || i >= PQntuples(result)) { rb_raise(rb_eArgError,"invalid tuple number %d", i); } if (j < 0 || j >= PQnfields(result)) { rb_raise(rb_eArgError,"invalid field number %d", j); } return INT2FIX(PQgetlength(result, i, j)); }
Returns the value in tuple number tup_num, field
field_num, or nil
if the field is NULL
.
static VALUE pgresult_getvalue(VALUE self, VALUE tup_num, VALUE field_num) { t_pg_result *this = pgresult_get_this_safe(self); int i = NUM2INT(tup_num); int j = NUM2INT(field_num); if(i < 0 || i >= PQntuples(this->pgresult)) { rb_raise(rb_eArgError,"invalid tuple number %d", i); } if(j < 0 || j >= PQnfields(this->pgresult)) { rb_raise(rb_eArgError,"invalid field number %d", j); } return this->p_typemap->funcs.typecast_result_value(this->p_typemap, self, i, j); }
# File lib/pg/result.rb, line 18 def inspect str = self.to_s str[-1,0] = " status=#{res_status(result_status)} ntuples=#{ntuples} nfields=#{nfields} cmd_tuples=#{cmd_tuples}" str end
Apply a type map for all value retrieving methods.
type_map
: a PG::TypeMap instance.
See PG::BasicTypeMapForResults
# File lib/pg/result.rb, line 13 def map_types!(type_map) self.type_map = type_map self end
Returns the number of columns in the query result.
static VALUE pgresult_nfields(VALUE self) { return INT2NUM(PQnfields(pgresult_get(self))); }
Returns the number of parameters of a prepared statement. Only useful for the result returned by conn.describePrepared
static VALUE pgresult_nparams(VALUE self) { PGresult *result; result = pgresult_get(self); return INT2FIX(PQnparams(result)); }
Returns the number of tuples in the query result.
static VALUE pgresult_ntuples(VALUE self) { return INT2FIX(PQntuples(pgresult_get(self))); }
Returns the oid
of the inserted row if applicable, otherwise
nil
.
static VALUE pgresult_oid_value(VALUE self) { Oid n = PQoidValue(pgresult_get(self)); if (n == InvalidOid) return Qnil; else return UINT2NUM(n); }
Returns the Oid of the data type of parameter param_number. Only useful for the result returned by conn.describePrepared
static VALUE pgresult_paramtype(VALUE self, VALUE param_number) { PGresult *result; result = pgresult_get(self); return UINT2NUM(PQparamtype(result,NUM2INT(param_number))); }
Returns the string representation of status status
.
static VALUE pgresult_res_status(VALUE self, VALUE status) { VALUE ret = rb_tainted_str_new2(PQresStatus(NUM2INT(status))); PG_ENCODING_SET_NOCHECK(ret, ENCODING_GET(self)); return ret; }
Returns the status of the query. The status value is one of:
-
PGRES_EMPTY_QUERY
-
PGRES_COMMAND_OK
-
PGRES_TUPLES_OK
-
PGRES_COPY_OUT
-
PGRES_COPY_IN
-
PGRES_BAD_RESPONSE
-
PGRES_NONFATAL_ERROR
-
PGRES_FATAL_ERROR
-
PGRES_COPY_BOTH
static VALUE pgresult_result_status(VALUE self) { return INT2FIX(PQresultStatus(pgresult_get(self))); }
Invokes block for each tuple in the result set in single row mode.
This is a convenience method for retrieving all result tuples as they are transferred. It is an alternative to repeated calls of PG::Connection#get_result , but given that it avoids the overhead of wrapping each row into a dedicated result object, it delivers data in nearly the same speed as with ordinary results.
The result must be in status PGRES_SINGLE_TUPLE. It iterates over all tuples until the status changes to PGRES_TUPLES_OK. A PG::Error is raised for any errors from the server.
Row description data does not change while the iteration. All value
retrieval methods refer to only the current row. #ntuples returns 1
while the iteration and 0
after all tuples were yielded.
Example:
conn.send_query( "first SQL query; second SQL query" ) conn.set_single_row_mode conn.get_result.stream_each do |row| # do something with the received row of the first query end conn.get_result.stream_each do |row| # do something with the received row of the second query end conn.get_result # => nil (no more results)
static VALUE pgresult_stream_each(VALUE self) { t_pg_result *this; int nfields; PGconn *pgconn; PGresult *pgresult; RETURN_ENUMERATOR(self, 0, NULL); this = pgresult_get_this_safe(self); pgconn = pg_get_pgconn(this->connection); pgresult = this->pgresult; nfields = PQnfields(pgresult); for(;;){ int tuple_num; int ntuples = PQntuples(pgresult); switch( PQresultStatus(pgresult) ){ case PGRES_TUPLES_OK: if( ntuples == 0 ) return self; rb_raise( rb_eInvalidResultStatus, "PG::Result is not in single row mode"); case PGRES_SINGLE_TUPLE: break; default: pg_result_check( self ); } for(tuple_num = 0; tuple_num < ntuples; tuple_num++) { rb_yield(pgresult_aref(self, INT2NUM(tuple_num))); } if( !this->autoclear ){ PQclear( pgresult ); this->pgresult = NULL; } pgresult = gvl_PQgetResult(pgconn); if( pgresult == NULL ) rb_raise( rb_eNoResultError, "no result received - possibly an intersection with another result retrieval"); if( nfields != PQnfields(pgresult) ) rb_raise( rb_eInvalidChangeOfResultFields, "number of fields must not change in single row mode"); this->pgresult = pgresult; } /* never reached */ return self; }
Yields each row of the result set in single row mode. The row is a list of column values.
This method works equally to stream_each , but yields an Array of values.
static VALUE pgresult_stream_each_row(VALUE self) { t_pg_result *this; int row; int nfields; PGconn *pgconn; PGresult *pgresult; RETURN_ENUMERATOR(self, 0, NULL); this = pgresult_get_this_safe(self); pgconn = pg_get_pgconn(this->connection); pgresult = this->pgresult; nfields = PQnfields(pgresult); for(;;){ int ntuples = PQntuples(pgresult); switch( PQresultStatus(pgresult) ){ case PGRES_TUPLES_OK: if( ntuples == 0 ) return self; rb_raise( rb_eInvalidResultStatus, "PG::Result is not in single row mode"); case PGRES_SINGLE_TUPLE: break; default: pg_result_check( self ); } for ( row = 0; row < ntuples; row++ ) { PG_VARIABLE_LENGTH_ARRAY(VALUE, row_values, nfields, PG_MAX_COLUMNS) int field; /* populate the row */ for ( field = 0; field < nfields; field++ ) { row_values[field] = this->p_typemap->funcs.typecast_result_value(this->p_typemap, self, row, field); } rb_yield( rb_ary_new4( nfields, row_values )); } if( !this->autoclear ){ PQclear( pgresult ); this->pgresult = NULL; } pgresult = gvl_PQgetResult(pgconn); if( pgresult == NULL ) rb_raise( rb_eNoResultError, "no result received - possibly an intersection with another result retrieval"); if( nfields != PQnfields(pgresult) ) rb_raise( rb_eInvalidChangeOfResultFields, "number of fields must not change in single row mode"); this->pgresult = pgresult; } /* never reached */ return self; }
Returns the TypeMap that is currently set for type casts of result values to ruby objects.
static VALUE pgresult_type_map_get(VALUE self) { t_pg_result *this = pgresult_get_this(self); return this->typemap; }
Set the TypeMap that is used for type casts of result values to ruby objects.
All value retrieval methods will respect the type map and will do the type casts from PostgreSQL's wire format to Ruby objects on the fly, according to the rules and decoders defined in the given typemap.
typemap
must be a kind of PG::TypeMap .
static VALUE pgresult_type_map_set(VALUE self, VALUE typemap) { t_pg_result *this = pgresult_get_this(self); t_typemap *p_typemap; if ( !rb_obj_is_kind_of(typemap, rb_cTypeMap) ) { rb_raise( rb_eTypeError, "wrong argument type %s (expected kind of PG::TypeMap)", rb_obj_classname( typemap ) ); } Data_Get_Struct(typemap, t_typemap, p_typemap); this->typemap = p_typemap->funcs.fit_to_result( typemap, self ); this->p_typemap = DATA_PTR( this->typemap ); return typemap; }
Returns all tuples as an array of arrays.
static VALUE pgresult_values(VALUE self) { t_pg_result *this = pgresult_get_this_safe(self); int row; int field; int num_rows = PQntuples(this->pgresult); int num_fields = PQnfields(this->pgresult); VALUE results = rb_ary_new2( num_rows ); for ( row = 0; row < num_rows; row++ ) { PG_VARIABLE_LENGTH_ARRAY(VALUE, row_values, num_fields, PG_MAX_COLUMNS) /* populate the row */ for ( field = 0; field < num_fields; field++ ) { row_values[field] = this->p_typemap->funcs.typecast_result_value(this->p_typemap, self, row, field); } rb_ary_store( results, row, rb_ary_new4( num_fields, row_values ) ); } return results; }