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This allows using text position search functions with nondeterministic collations. These functions are - position, strpos - replace - split_part - string_to_array - string_to_table which all use common internal infrastructure. There was previously no internal implementation of this, so it was met with a not-supported error. This adds the internal implementation and removes the error. Unlike with deterministic collations, the search cannot use any byte-by-byte optimized techniques but has to go substring by substring. We also need to consider that the found match could have a different length than the needle and that there could be substrings of different length matching at a position. In most cases, we need to find the longest such substring (greedy semantics), but this can be configured by each caller. Reviewed-by: Euler Taveira <euler@eulerto.com> Discussion: https://www.postgresql.org/message-id/flat/582b2613-0900-48ca-8b0d-340c06f4d400@eisentraut.org