Subject | Re: [firebird-support] Re: Primary Key of character a problem? |
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Author | Ann Harrison |
Post date | 2003-07-30T22:47:05Z |
Raymond,
sorry to take so long in answering - got tied up in a different problem.
binary 7. If more leading characters duplicate the previous index
entry, then they'll be compressed too. Generally, your key will consist
of a binary 19 and the last byte of the LocalCount, or 19 and the last
two bytes of LocalCount.
Regards,
Ann
Regards,
sorry to take so long in answering - got tied up in a different problem.
>I was thinking (and that is a frightening thing<grin>) that the internal binary trees would be the most efficient if I had a nice even distribution over the values... so in this thinking, I created the PK like this: (remember my PK is a string)PK:=LocalCount+MachineID+MfgID+PlanetID+SolarSysID+GalaxyIDThat's backward from the point of view of prefix compression.
>
>
>If Galaxy, SolarSys, and Planet were first, well I would have to look at all the letters and all would be the same up until I finally arrived at the 7th character and then I would finally be able to start to narrow down the search...Ah, but prefix compression turns those seven characters into a single
>
binary 7. If more leading characters duplicate the previous index
entry, then they'll be compressed too. Generally, your key will consist
of a binary 19 and the last byte of the LocalCount, or 19 and the last
two bytes of LocalCount.
Regards,
Ann
Regards,