DbColumn = object
  name*: string              ## name of the column
  tableName*: string         ## name of the table the column belongs to (optional)
  typ*: DbType               ## type of the column
  primaryKey*: bool          ## is this a primary key?
  foreignKey*: bool          ## is this a foreign key?
  

DbColumns = seq[DbColumn]

DbEffect = object of IOEffect

DbError = object of IOError

DbType = object
  kind*: DbTypeKind          ## the kind of the described type
  notNull*: bool             ## does the type contain NULL?
  name*: string              ## the name of the type
  size*: Natural             ## the size of the datatype; 0 if of variable size
  maxReprLen*: Natural       ## maximal length required for the representation
  precision*, scale*: Natural ## precision and scale of the number
  min*, max*: BiggestInt     ## the minimum and maximum of allowed values
  validValues*: seq[string]  ## valid values of an enum or a set
  

DbTypeKind = enum
  dbUnknown,                ## unknown datatype
  dbSerial,                 ## datatype used for primary auto-increment keys
  dbNull,                   ## datatype used for the NULL value
  dbBit,                    ## bit datatype
  dbBool,                   ## boolean datatype
  dbBlob,                   ## blob datatype
  dbFixedChar,              ## string of fixed length
  dbVarchar,                ## string datatype
  dbJson,                   ## JSON datatype
  dbXml,                    ## XML datatype
  dbInt,                    ## some integer type
  dbUInt,                   ## some unsigned integer type
  dbDecimal,                ## decimal numbers (fixed-point number)
  dbFloat,                  ## some floating point type
  dbDate,                   ## a year-month-day description
  dbTime,                   ## HH:MM:SS information
  dbDatetime,               ## year-month-day and HH:MM:SS information,
                             ## plus optional time or timezone information
  dbTimestamp, ## Timestamp values are stored as the number of seconds
                ## since the epoch ('1970-01-01 00:00:00' UTC).
  dbTimeInterval,           ## an interval [a,b] of times
  dbEnum,                   ## some enum
  dbSet,                    ## set of enum values
  dbArray,                  ## an array of values
  dbComposite,              ## composite type (record, struct, etc)
  dbUrl,                    ## a URL
  dbUuid,                   ## a UUID
  dbInet,                   ## an IP address
  dbMacAddress,             ## a MAC address
  dbGeometry,               ## some geometric type
  dbPoint,                  ## Point on a plane   (x,y)
  dbLine,                   ## Infinite line ((x1,y1),(x2,y2))
  dbLseg,                   ## Finite line segment   ((x1,y1),(x2,y2))
  dbBox,                    ## Rectangular box   ((x1,y1),(x2,y2))
  dbPath,                   ## Closed or open path (similar to polygon) ((x1,y1),...)
  dbPolygon,                ## Polygon (similar to closed path)   ((x1,y1),...)
  dbCircle,                 ## Circle   <(x,y),r> (center point and radius)
  dbUser1,                  ## user definable datatype 1 (for unknown extensions)
  dbUser2,                  ## user definable datatype 2 (for unknown extensions)
  dbUser3,                  ## user definable datatype 3 (for unknown extensions)
  dbUser4,                  ## user definable datatype 4 (for unknown extensions)
  dbUser5                    ## user definable datatype 5 (for unknown extensions)

ReadDbEffect = object of DbEffect

SqlQuery = distinct string

WriteDbEffect = object of DbEffect

proc dbError(msg: string) {.noreturn, noinline, ...raises: [DbError], tags: [].}

template sql(query: string): SqlQuery