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| -rw-r--r-- | doc/src/sgml/ref/create_index.sgml | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml index 43b6499603c..f7f360875c2 100644 --- a/doc/src/sgml/ref/create_index.sgml +++ b/doc/src/sgml/ref/create_index.sgml @@ -381,7 +381,16 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ <replaceable class="parameter">name</ <para> In a concurrent index build, the index is actually entered into the system catalogs in one transaction, then the two table scans occur in a - second and third transaction. + second and third transaction. All active transactions at the time the + second table scan starts, not just ones that already involve the table, + have the potential to block the concurrent index creation until they + finish. When checking for transactions that could still use the original + index, concurrent index creation advances through potentially interfering + older transactions one at a time, obtaining shared locks on their virtual + transaction identifiers to wait for them to complete. + </para> + + <para> If a problem arises while scanning the table, such as a uniqueness violation in a unique index, the <command>CREATE INDEX</> command will fail but leave behind an <quote>invalid</> index. This index |