Mysql when was table analyzed

Any existing histogram statistics remain unaffected. If the table has not changed since the last key distribution analysis, the table is not analyzed again. MySQL uses the stored key distribution to decide the order in which tables should be joined for joins on something other than a constant.

In addition, key distributions can be used when deciding which indexes to use for a specific table within a query. See Section For more information about key distribution analysis in InnoDB , see Section MySQL uses index cardinality estimates in join optimization.

See Section B. For information about histogram statistics, see Section 8. The value of N must be an integer in the range from 1 to If this clause is omitted, the number of buckets is Stored histogram management statements affect only the named columns. Consider these statements:. The first statement updates the histograms for columns c1 , c2 , and c3 , replacing any existing histograms for those columns.

The second statement updates the histograms for c1 and c3 , leaving the c2 histogram unaffected. The third statement removes the histogram for c2 , leaving those for c1 and c3 unaffected.

Histogram generation applies to columns of all data types except geometry types spatial data and JSON. Histograms cannot be generated for columns that are covered by single-column unique indexes. Histogram management statements attempt to perform as much of the requested operation as possible, and report diagnostic messages for the remainder. Instead, it renames histograms for the renamed table to be associated with the new table name. Histograms for noncharacter columns remain unaffected.

The global and session values may be set at runtime. See Section 5. Sampling is evenly distributed over the entire table. You are correct. What InnoDB does instead is the following:.

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Boolean Boolean 1 1 gold badge 5 5 silver badges 10 10 bronze badges. Add a comment. Active Oldest Votes. This is not the same for InnoDB. When should run Analyze table statement in mysql Ask Question. Asked 1 year, 5 months ago. Active 8 months ago. Viewed 1k times. It seems that MySQL doesn't store when the last time "stat" was updated? Improve this question. Add a comment. Active Oldest Votes. Improve this answer. Bill Karwin Bill Karwin 8, 1 1 gold badge 25 25 silver badges 35 35 bronze badges.

Because it time consuming on large tables and every new entry would can change tge dynamic. InnoDB does a small number of probes; it is not "time consuming on large tables". MyISAM, on the other hand, looks at the entire table. Sign up or log in Sign up using Google.