From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Yury Zhuravlev <u(dot)zhuravlev(at)postgrespro(dot)ru> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Some questions about the array. |
Date: | 2015-12-23 02:15:03 |
Message-ID: | 4475.1450836903@sss.pgh.pa.us |
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Yury Zhuravlev <u(dot)zhuravlev(at)postgrespro(dot)ru> writes:
> New patch version in attachment.
I've committed this with a number of revisions, mostly but not entirely
cosmetic. Worthy of note:
* I did not like the way you were inserting the replacement subscript
values:
+ arrays = (AnyArrayType *)DatumGetArrayTypeP(array_source);
+ indexexpr = AARR_LBOUND(arrays)[i] + AARR_DIMS(arrays)[i] - 1;
If the source array is toasted, this causes an extra detoast operation
for *each* omitted subscript. That could be pretty high overhead for
a large array. The best way to avoid that is to postpone the actual
substitution of the replacement subscript values into array_get_slice
and array_set_slice; which complicates their APIs a bit more, but those
were pretty long argument lists already.
* Having done that, there was no very good reason for the blanket
prohibition on using omitted subscripts in the slice-set case. We only
really need to fail if we're constructing the array from scratch, when
we don't have any existing subscript limits to substitute.
regards, tom lane
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