Bug 116502 – Optimized querySelector(All) when selector contains #id

• Status: RESOLVED
• Resolution: FIXED
• Component: DOM

[Ryosuke Niwa]

Consider implementing the same optimization as https://chromium.googlesource.com/chromium/blink/+/1cd83d3588973a02ab15d94b1b05a28620853624.

There existed an optimization that did an element lookup for an id if the
leftmost part of the selector was an id selector. Without this change, these
queries would do an id lookup:

querySelector("#id"), querySelector("#id.class")

while these wouldn't:

querySelector(".class#id"), querySelector("[name=x]#id")

This change modifies the element lookup to include the latter two.

More importantly, it also extends the optimization for id selectors to limit
traversal of the dom-tree to the sub-tree rooted at the element with an id
matching the rightmost id selector in the whole selector. For id selectors
appearing left of adjacent combinators, the traversal needs to be rooted at
the parent of the element with the given id.

Examples:

querySelector("#id span") - traversal from the id element.
querySelector("#id + div span") - traversal from the parent of the id element.

This fix should make this:

querySelector("#id span")

as fast as:

getElementById("id").querySelector("span")

[Benjamin Poulain]

Created attachment 225028 [details]
Patch

[Andreas Kling]

Comment on attachment 225028 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=225028&action=review

r=me

> Source/WebCore/ChangeLog:13
> +        cache, and start matching the childre from there.

Typo, children.

> Source/WebCore/dom/SelectorQuery.cpp:246
> +            if (LIKELY(!rootNode.treeScope().containsMultipleElementsWithId(idToMatch))) {
> +                if (ContainerNode* searchRoot = rootNode.treeScope().getElementById(idToMatch)) {

It would be more efficient to do these two checks in opposite order.

> Source/WebCore/dom/SelectorQuery.cpp:417
> +        CompiledSingleWithRootFilterCase:

Indentation is off here.

> Source/WebCore/dom/SelectorQuery.h:49
> -    void initialize(const CSSSelectorList&);
> +    SelectorDataList(const CSSSelectorList&);

explicit

[Benjamin Poulain]

Created attachment 225557 [details]
Patch

[Benjamin Poulain]

Created attachment 225558 [details]
Patch

[Benjamin Poulain]

Committed r164924: <http://trac.webkit.org/changeset/164924>