PS-10289 (8.0) Fix digest normalization for unary operators

[yakirgb]

This patch fixes digest normalization for unary operators after comparison operators and CASE keywords.

Queries like "WHERE a = 1" and "WHERE a = -1" now correctly produce the same digest, which is important for proper query grouping in Performance Schema.

Files modified:

• sql/gen_lex_token.cc (marks comparison operators and CASE keywords as start_expr)
• mysql-test/suite/perfschema/t/unary_digest.test
• mysql-test/suite/perfschema/r/unary_digest.result

Simple test:

USE performance_schema;
SELECT
STATEMENT_DIGEST_TEXT('SELECT * FROM t WHERE a = 1') =
STATEMENT_DIGEST_TEXT('SELECT * FROM t WHERE a = -1') AS digests_match;

SELECT
STATEMENT_DIGEST_TEXT('SELECT * FROM t WHERE a < 1') =
STATEMENT_DIGEST_TEXT('SELECT * FROM t WHERE a < -1') AS digests_match;

SELECT
STATEMENT_DIGEST_TEXT('SELECT CASE WHEN a > 0 THEN 1 END FROM t') =
STATEMENT_DIGEST_TEXT('SELECT CASE WHEN a > 0 THEN -1 END FROM t') AS digests_match;

SELECT
STATEMENT_DIGEST_TEXT('SELECT CASE WHEN a > 0 THEN 1 ELSE 2 END FROM t') = STATEMENT_DIGEST_TEXT('SELECT CASE WHEN a > 0 THEN -1 ELSE -2 END FROM t') AS digests_match;

Thank you,
Yakir Gibraltar

[yakirgb]

Hi, @percona-ysorokin WDYT?