Normalize: Match GROUP BY against target list and re-use param refs #124
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
lfittl
force-pushed
the
13-latest-normalize-group-by-targetlist-match
branch
2 times, most recently
from
176bfb2 to
9680717
Compare
This avoids "columns ... must appear in the GROUP BY clause ..." type errors when the normalize result is utilized as a parameterized query with Postgres. We reuse the pg_query fingerprinting logic to determine whether a target list element is identical with a GROUP BY element. Note that query data coming from pg_stat_statements normalizes the target list, but not the GROUP BY list. Additionally, this overly optimizes for reusing param refs, specifically when the target list contains elements that are similar, but not 100% identical, we err on matching them (based on the pg_query fingerprint), instead of requiring full equivalency. e.g. the target list may contain a certain string constant and we would consider any other string constant in the GROUP BY to be equivalent (since they have the same fingerprint).
lfittl
force-pushed
the
13-latest-normalize-group-by-targetlist-match
branch
from
9680717 to
b47233d
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This avoids "columns ... must appear in the GROUP BY clause ..." type
errors when the normalize result is utilized as a parameterized query
with Postgres. We reuse the pg_query fingerprinting logic to determine
whether a target list element is identical with a GROUP BY element.
Note that query data coming from pg_stat_statements normalizes the target
list, but not the GROUP BY list.
Additionally, this overly optimizes for reusing param refs, specifically
when the target list contains elements that are similar, but not 100%
identical, we err on matching them (based on the pg_query fingerprint),
instead of requiring full equivalency. e.g. the target list may contain
a certain string constant and we would consider any other string constant
in the GROUP BY to be equivalent (since they have the same fingerprint).