Re: [HACKERS] GiST -- making my index faster makes is slower

[David Blasby]

Humm -- strange results here:

typedef struct
{
        float xmin;
        float ymin;
        float xmax;
        float ymax;
} BOX2DFLOAT4;
This takes about 18,000 ms to do a nested query with 10,000 iterations.

typedef struct
{
        float xmin;
        float ymin;
        float xmax;
        float ymax;
        char  junk[16];
} BOX2DFLOAT4;
This takes about 15,000 ms to do a nested query with 10,000 iterations.

typedef struct
{
        double xmin;
        double ymin;
        double xmax;
        double ymax;
} BOX2DFLOAT4;
This takes about 1500 ms to do a nested query with 10,000 iterations.
Yes - that almost 14 seconds faster!
This doesnt make a lot of sense since the only part of the GiST index 
thats being called that actually looks at the bounding boxes is this:

 retval = (((key->xmax>= query->xmax) &&
          (key->xmin <= query->xmax)) ||
          ((query->xmax>= key->xmax) &&
          (query->xmin<= key->xmax)))
             &&
          (((key->ymax>= query->ymax) &&
          (key->ymin<= query->ymax)) ||
          ((query->ymax>= key->ymax) &&
          (query->ymin<= key->ymax)));
dave

---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
     joining column's datatypes do not match