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Philipp Shergalis commented on IGNITE-23120: -------------------------------------------- [~timonin.maksim] Hi! Thanks for reviewing. For loop in *computeInlineSize* serves two puproses: calculate total index size and check if {*}all fields have fixed size{*}. But we break this loop early if calculated size exceeds *propSize* Consider that the *last field* in the index has *not fixed size* and earlier fields ({*}with fixed size{*}) will exceed {*}propSize{*}. Then we hit condition *size > propSize,* break for-loop early and variable *fixedSize* will be true. But it must be false because of the last field if (size > propSize) { size = propSize; break; } > Improve inline index feature > ---------------------------- > > Key: IGNITE-23120 > URL: https://issues.apache.org/jira/browse/IGNITE-23120 > Project: Ignite > Issue Type: Improvement > Reporter: Vladimir Pligin > Assignee: Philipp Shergalis > Priority: Major > Time Spent: 0.5h > Remaining Estimate: 0h > > Ignite allows index rows to be inlined directly into the page. However, it > doesn’t guard properly against too big inline size values. Currently, it uses > {{PageIO.MAX_PAYLOAD_SIZE}} as the maximum allowed value, but this value can > still be too large, because it does not take the page size and encryption > (which adds additional bytes to the page header) into account. This possibly > leads to a bad situation when only one item can fit in one page which can > lead to BTree performance degradation. > The following is expected to be done: > # When inline size for an index is set, a maximum inline size should be > computed: > ## Considering we want to have _at least_ 2 items per page, here’s how the > page layout with max inline size will look like: {{PS = H + L + I + L + I + > L}} . Where PS - Page Size, H - page header size, L - size of the child link, > I - item size. > ## Using the above equation, we get the max possible item size to be equal > to: {{I = (PS - H - 3L) / 2}} . However, for inline indexes, every item has > an additional overhead to the actual inlined value (a.k.a payload), which > depends on MVCC being present. > ## Taking this into account, the maximum payload size will be equal: {{P = > (PS - H - 3L) / 2 - X}} , where P - Payload size, X - overhead per item. > ## In implementation terms, {{PS}} must be computed using the > {{PageMemory#realPageSize}} which takes encryption overhead into > account,{{{}H{}}} is equal to {{{}BPlusIo#ITEMS_OFF{}}}, {{L}} is 8 bytes and > {{X}} depends on the actual {{AbstractH2ExtrasInnerIO}} implementation and > varies between 8 and 28 bytes. > # If the configured inline size exceeds the computed maximum size or > {{PageIO.MAX_PAYLOAD_SIZE}} then an exception must be thrown with a message > that notifies the user of the incorrect inline size value. Note that this > should only happen for _new_ indexes, if a nodes is started on top of an > existing PDS, no exceptions should be thrown and a warning should be printed > instead, to preserve backwards compatibility. > # Fix the “Indexed columns of a row cannot be fully inlined into index” > warning to recommend at most the maximum allowed inline size. -- This message was sent by Atlassian Jira (v8.20.10#820010)