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perf(sql): offset scanner for leading comments in sql_limit (#1515) - #1612
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…ndLineComments Each leading comment copied the rest of the script (substring + trimLeft), so a dump with a long header of comment lines in front of a large script was quadratic in memory. An index walks whitespace, -- lines and nested /* */ blocks and the string is sliced once. The whitespace set is the one trimLeft uses. A test compares the result with the previous implementation on listed and random scripts. Closes #1515
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Summary
stripLeadingWhitespaceAndLineCommentsdids.substring(nl + 1).trimLeft()/s.substring(blockEnd).trimLeft()for every leading comment, so a 10 MB dump with 50 header lines copied the remaining script 50 times before the query ran._skipLeadingCommentsOffsetwalks an index through whitespace (the exact settrimLeftremoves),--lines (to\n, as before) and nested/* */blocks (reusing_blockCommentEndfrom the same offset), and the function slices once. A script that is all comment / whitespace still gives''.Callers (
injectSqlLimit,postgres_sql.dart,postgres_table_utils.dart) are unchanged.Tests (not run locally; CI will)
test/core/database/sql_limit_strip_test.dartkeeps the old implementation as the reference and compares about 25 listed scripts (CRLF, nested and unterminated blocks, only-comment scripts,--without a newline,\u0085/), 4000 seeded random scripts, and a 500-line header in front of a large body. The existingsql_limit_test.dartis untouched.Closes #1515