Module: PgQuery::Deparse::Interval

Defined in:
lib/pg_query/deparse/interval.rb

Constant Summary collapse

MASKS =

From src/include/utils/datetime.h The number is the power of 2 used for the mask.

{
  0  => 'RESERV',
  1  => 'MONTH',
  2  => 'YEAR',
  3  => 'DAY',
  4  => 'JULIAN',
  5  => 'TZ',
  6  => 'DTZ',
  7  => 'DYNTZ',
  8  => 'IGNORE_DTF',
  9  => 'AMPM',
  10 => 'HOUR',
  11 => 'MINUTE',
  12 => 'SECOND',
  13 => 'MILLISECOND',
  14 => 'MICROSECOND',
  15 => 'DOY',
  16 => 'DOW',
  17 => 'UNITS',
  18 => 'ADBC',
  19 => 'AGO',
  20 => 'ABS_BEFORE',
  21 => 'ABS_AFTER',
  22 => 'ISODATE',
  23 => 'ISOTIME',
  24 => 'WEEK',
  25 => 'DECADE',
  26 => 'CENTURY',
  27 => 'MILLENNIUM',
  28 => 'DTZMOD'
}.freeze
KEYS = 
MASKS.invert
SQL_BY_MASK =

Postgres stores the interval ‘day second’ as ‘day hour minute second’ so we need to reconstruct the sql with only the largest and smallest time values. Since the rules for this are hardcoded in the grammar (and the above list is not sorted in any sensible way) it makes sense to hardcode the patterns here, too.

This hash takes the form:

    { (1 << 1) | (1 << 2) => 'year to month' }

Which is:

    { 6 => 'year to month' }

{
  (1 << KEYS['YEAR'])     => %w[year],
  (1 << KEYS['MONTH'])    => %w[month],
  (1 << KEYS['DAY'])      => %w[day],
  (1 << KEYS['HOUR'])     => %w[hour],
  (1 << KEYS['MINUTE'])   => %w[minute],
  (1 << KEYS['SECOND'])   => %w[second],
  (1 << KEYS['YEAR'] |
     1 << KEYS['MONTH'])  => %w[year month],
  (1 << KEYS['DAY'] |
     1 << KEYS['HOUR'])   => %w[day hour],
  (1 << KEYS['DAY'] |
     1 << KEYS['HOUR'] |
     1 << KEYS['MINUTE']) => %w[day minute],
  (1 << KEYS['DAY'] |
     1 << KEYS['HOUR'] |
     1 << KEYS['MINUTE'] |
     1 << KEYS['SECOND']) => %w[day second],
  (1 << KEYS['HOUR'] |
     1 << KEYS['MINUTE']) => %w[hour minute],
  (1 << KEYS['HOUR'] |
     1 << KEYS['MINUTE'] |
     1 << KEYS['SECOND']) => %w[hour second],
  (1 << KEYS['MINUTE'] |
     1 << KEYS['SECOND']) => %w[minute second]
}.freeze

Class Method Summary collapse

Class Method Details

.from_int(int) ⇒ Object

A type called ‘interval hour to minute’ is stored in a compressed way by simplifying ‘hour to minute’ to a simple integer. This integer is computed by looking up the arbitrary number (always a power of two) for ‘hour’ and the one for ‘minute’ and XORing them together.

For example, when parsing “interval hour to minute”:

HOUR_MASK = 10
MINUTE_MASK = 11
mask = (1 << 10) | (1 << 11)
mask = 1024 | 2048
mask =     (010000000000
                xor
            100000000000)
mask =      110000000000
mask = 3072

Postgres will store this type as 'interval,3072'
We deparse it by simply reversing that process.



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# File 'lib/pg_query/deparse/interval.rb', line 24

def self.from_int(int)
  SQL_BY_MASK[int]
end