stiga-huang opened a new pull request, #2378:
URL: https://github.com/apache/hive/pull/2378
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### What changes were proposed in this pull request?
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This PR extends the INSTR() function to support optional position and
occurrence arguments, which is supported in Oracle, Impala, etc.
https://docs.oracle.com/database/121/SQLRF/functions089.htm#SQLRF00651
https://impala.apache.org/docs/build/html/topics/impala_string_functions.html#string_functions__instr
### Why are the changes needed?
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This provides users more functionality in the INSTR() function.
It also helps to reduce the SQL difference between Hive and Impala.
### Does this PR introduce _any_ user-facing change?
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Yes, INSTR() will have two more optional arguments, which needs document as
well.
```
instr(str, substr[, pos[, occurrence]]) - Returns the index of the given
occurrence of substr in str after position pos
pos is a 1-based index. If pos < 0, the starting position is
determined by counting backwards from the end of str and then Hive
searches backward from the resulting position.
occurrence is also a 1-based index. The value must be positive.
If occurrence is greater than the number of matching occurrences,
the function returns 0.
If either of the optional arguments, pos or occurrence, is NULL,
the function also returns NULL.
Example:
> SELECT instr('Facebook', 'boo') FROM src LIMIT 1;
5
> SELECT instr('CORPORATE FLOOR','OR', 3, 2) FROM src LIMIT 1;
14
> SELECT instr('CORPORATE FLOOR','OR', -3, 2) FROM src LIMIT 1;
2
```
### How was this patch tested?
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Tests were added in udf_instr_wrong_args_len2.q,
udf_instr_wrong_occurrence.q, and udf_instr.q.
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