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Trailing escape ('ab\') is disallowed in SQL, in standardese:
"If an escape character is specified, then [...] If there is not a
partitioning of the string PVC into substrings such that each substring
has length 1 (one) or 2, no substring of length 1 (one) is the escape
character ECV, and each substring of length 2 is the escape character
ECV followed by either the escape character ECV, an <underscore>
character, or the <percent> character, then an exception condition is
raised: data exception - invalid escape sequence."
I first thought this is checked already higher up in the stack, at least
for const needles, as single trailing backslashes ('ab\') are rejected,
but then I realized that ClickHouse quotes by default. I.e., double
trailing backslashes ('ab\\') are not rejected but when interpreted as
LIKE needle ('ab\') they should.
14 lines
362 B
SQL
14 lines
362 B
SQL
DROP TABLE IF EXISTS tab;
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CREATE TABLE tab (haystack String, pattern String) engine = MergeTree() ORDER BY haystack;
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INSERT INTO tab VALUES ('haystack', 'pattern\\');
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-- const pattern
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SELECT haystack LIKE 'pattern\\' from tab; -- { serverError 25 }
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-- non-const pattern
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SELECT haystack LIKE pattern from tab; -- { serverError 25 }
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DROP TABLE IF EXISTS tab;
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