Tom Lane wrote: > Bruce Momjian <[EMAIL PROTECTED]> writes: > > So, my understanding is that you would create something such as: > > CREATE INDEX iix ON tab (LIKE col) > > and that does LIKE lookups and knows how to do col LIKE 'abc%', but it > > can't be used for >= or ORDER BY, but it can be used for equality tests? > > Hm. Right at the moment, it wouldn't be used for equality tests unless > you spelled equality as "a ~=~ b". I wonder whether that's necessary > though; couldn't we dispense with that operator and use ordinary > equality as the BTEqual member of these opclasses? Are there any > locales that claim that not-physically-identical strings are equal?
Let me see if I understand. Our default indexes will be able to do =, >, <, ORDER BY, and the special index will be able to do LIKE, ORDER BY, and maybe equals. Do I have that correct? Looking at CVS, I see the warning about non-C locales has been removed. Should we instead mention the new LIKE index method? # (Be sure to maintain the correspondence with locale_is_like_safe() in selfuncs.c.) if test x`pg_getlocale COLLATE` != xC && test x`pg_getlocale COLLATE` != xPOSIX; then echo "This locale setting will prevent the use of indexes for pattern matching" echo "operations. If that is a concern, rerun $CMDNAME with the collation order" echo "set to \"C\". For more information see the Administrator's Guide." fi Doing LIKE with single-byte encodings would be easy because it would be only 256 compares to find the min/max char values, but that doesn't work with multi-byte encodings, right? This LIKE/encoding problem is a tricky one because it gives poor performance with little warning to users. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])