Stewart Smith wrote:
On Mon, Oct 12, 2009 at 01:49:40PM -0400, Jay Pipes wrote:
Here is relevant piece of the current proto:
message Field {
...
message FieldOptions {
optional string default_value = 1;
optional string update_value = 2;
optional bool default_null = 3 [default = false];
optional bytes default_bin_value = 4;
optional int32 length = 100; /* TODO: should go away */
}
...
optional FieldOptions options = 4;
Here is a proposed modification which would allow for a vast number of
functions to be used as defaults:
message Field {
...
message FieldDefault {
enum FieldDefaultType {
CONSTANT = 0;
FUNCTION = 1;
/* possible FIELD later on... */
}
required DefaultType type = 1; /* The type of the default value */
required bytes default_value = 2; /* The actual value */
repeated bytes args = 3; /* Array of function arguments */
}
...
optional FieldDefault default = 4;
}
The above would allow a fairly future-proof method of constructing
variable defaults which could include functions with any number of
arguments.
why this (more complex) structure instead of just the norm which is
default_value being an expression? (with the "bug" of currently just
being constant or "NOW()").
Because it's not a hack. The above FieldDefault message definition is
flexible enough to allow for all types of items used as defaults...such
as other fields, SQL expressions, etc. Storing it all in a string means
the FieldDefault message does not describe the default. It isn't
descriptive at all...
The only reason there is the default_bin_value there is that we can/need/should
support wacky things like a default value of a series of null bytes.
This is why the data member default_value is of type bytes, not string.
During mysql_insert(), having such a structure in the Field message
would allow us to easily create an appropriate Item_string or Item_func
depending on the value of default.type.
We should have the ability for the engines to take over responsibility
for some/all default values.
Could you explain the above a little more? I'm not quite sure what you
mean. Is there an example you are thinking of?
Thanks!
Jay
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