MDEV-38873 json_extract returns NULL through derived table#4680
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varundeepsaini wants to merge 1 commit intoMariaDB:10.11from
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MDEV-38873 json_extract returns NULL through derived table#4680varundeepsaini wants to merge 1 commit intoMariaDB:10.11from
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Thank you for your contribution.
This is a preliminary review.
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10.11 is the correct target at this point. Please rebase to that.
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Item_func_json_extract::fix_length_and_dec() underestimated max_length. The result is passed through json_nice() with LOOSE formatting which expands separators (e.g. ["a",1] -> ["a", 1]), but max_length was computed from the input size alone. When the result flows through a materialized derived table, the field is created with this too-small max_length and the output gets truncated. Fix: multiply by 2 to account for LOOSE expansion, add array framing overhead for multi-path extractions, and use fix_char_length_ulonglong() for proper character-to-byte conversion and overflow handling. Signed-off-by: Varun Deep Saini <varun.23bcs10048@ms.sst.scaler.com>
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LGTM. Please stand by for the final review.
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Description
json_extract()passes its result throughjson_nice()with LOOSE format, which expands the output by adding spaces after commas and colons (e.g.["a",1]→["a", 1]). Themax_lengthinItem_func_json_extract::fix_length_and_dec()was not accounting for this expansion. When the result passed through a derived table, the field was created with the underestimated length, truncating the JSON string and causing the outerjson_extract()to fail with "Unexpected end of JSON text".Fixed by multiplying
max_lengthby 2 to account for the LOOSE format expansion, matchingJSON_FORMAT(LOOSE)behavior.Release Notes
JSON_EXTRACT()no longer returns NULL with "Unexpected end of JSON text" when its result is used through a derived table.How can this PR be tested?
Basing the PR against the correct MariaDB version
mainbranch.PR quality check