Recall the first plan clues to inspect before changing SQL or indexes.
First clue in a slow plan? Find the node with the most time, rows, or loops, then trace what fed it. The expensive node may be downstream of an earlier cardinality mistake. Sequential scan: bad sign or reasonable plan? Sequential scans are often correct for broad reads. Can we add an index right now to fix the incident? A hot table already has many indexes and slow writes. Your line Maybe, but first we need the access pattern and plan evidence. An index speeds a read only if it lets the database skip work; it taxes every write. Do not…
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