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docs: Changing column type doesn't always require an index rebuild.

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Original file line number	Diff line number	Diff line change
`@@ -1366,7 +1366,13 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM`
`1366`	`1366`	`existing column, if the <literal>USING</literal> clause does not change`
`1367`	`1367`	`the column contents and the old type is either binary coercible to the new`
`1368`	`1368`	`type or an unconstrained domain over the new type, a table rewrite is not`
`1369`		`- needed; but any indexes on the affected columns must still be rebuilt.`
	`1369`	`+ needed. However, indexes must always be rebuilt unless the system can`
	`1370`	`+ verify that the new index would be logically equivalent to the existing`
	`1371`	`+ one. For example, if the collation for a column has been changed an index`
	`1372`	`+ rebuild is always required because the new sort order might be different.`
	`1373`	`+ However, in the absence of a collation change, a column can be changed`
	`1374`	`+ from <type>text</type> to <type>varchar</type> (or vice versa) without`
	`1375`	`+ rebuilding the indexes because these data types sort identically.`
`1370`	`1376`	`Table and/or index rebuilds may take a`
`1371`	`1377`	`significant amount of time for a large table; and will temporarily require`
`1372`	`1378`	`as much as double the disk space.`

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