Bring back the "|" symbol and eliminate search rakes #5436
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This commit brings back the "|" symbol for pipeline separator while retaining the "|>" as an option. The latter is needed to exit a SQL expression back into a pipe when a SQL expression is immediately followed by a shortcut that begins with an identifier (implied-yield expression or agg function). For any valid query without shortcuts, there is never an ambiguity between the bitwise OR "|" and pipe separator because keywords cannot be used as identifiers. The argument that such ambiguity is present made in the Google SQL pipes paper presumably assumes a one-token lookahead parser, which is not the case here. Toward this end, we changed our grammar to disallow keywords as identifier and added the backtick-string syntax to escape any string as identifier. Furthermore, we arranged for the expression grammar to include "|" for bitwise OR in SQL expression but omit it in any non-SQL pipe operator. This means any valid SQL queries will continue to be valid SuperSQL queries (inclusive of bitwise OR). Moreover, expressions in pipeline operators do not have any pipe-character ambiguity with shortcuts because bitwise-OR is omitted. We can add bitwise functionality as named functions in place of the archaic C-style syntax (which can work in both SQL and pipeline operators). Best practice will be to use these functions over the old bitwise syntax. We also removed search syntax as a shortcut and now require a "?" (or "search" keyword) to signal the keyword search operator. This means typos that happen to compile into unintended searches are no longer accepted by the grammar thereby eliminating the so-called search rake.
Ok as disccused, I'm pushing these changes to remove bitwise-OR from the SQL expression syntax, thus removing the ambiguity with the SQL shortcuts. If/when users want to run SuperSQL queries on legacy SQL with bitwise OR, we can put this grammar back in place but under a flag to enable it only as needed. In the meantime, wew ill introduce bitwise_or(), bitwise_and(), etc named functions in subsequent PR.
nwt
reviewed
Nov 5, 2024
nwt
approved these changes
Nov 5, 2024
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This commit brings back the "|" symbol for pipeline separator while retaining the "|>" as an option. The latter is needed to exit a SQL expression back into a pipe when a SQL expression is immediately followed by a shortcut that begins with an identifier (implied-yield expression or agg function).
For any valid query without shortcuts, there is never an ambiguity between the bitwise OR "|" and pipe separator because keywords cannot be used as identifiers. The argument that such ambiguity is present made in the Google SQL pipes paper presumably assumes a one-token lookahead parser, which is not the case here.
Toward this end, we changed our grammar to disallow keywords as identifier and added the backtick-string syntax to escape any string as identifier.
We also removed search syntax as a shortcut and now require a "?" (or "search" keyword) to signal the keyword search operator. This means typos that happen to compile into unintended searches are no longer accepted by the grammar thereby eliminating the so-called search rake.