This is how many blocks you processed in "consistent read" mode. This will include counts of blocks read from the rollback segment in order to roll back a block. This is the mode you read blocks in with a SELECT, for example. Also, when you do a searched UPDATE/DELETE, you read the...
loop inner join (cost=2.86 rows=4) (actual time=0.039,0.039,0.039..0.039,0.039,0.039 rows=0,0,0 loops=1,1,1) -> Nested loop inner join (cost=1.45 rows=1) (actual time=0.037,0.037,0.037..0.037,0.037,0.037 rows=0,0,0 loops=1,1,1) -> Parallel table scan on customer, with par...
This is how many blocks you processed in "consistent read" mode. This will include counts of blocks read from the rollback segment in order to roll back a block. This is the mode you read blocks in with a SELECT, for example. Also, when you do a searched UPDATE/DELETE, you read the...
‘ref’ column tells us which columns or constants are compared to the index picked by the optimizer. In our case this is ‘const’ as we are using a constant in the WHERE clause. This can be another column, for example in the case of a join. You can also see ‘func’ when we ar...
<derivedN>:ID值n的行的派生表结果,派生表可能是从FROM子句中的一个子查询生成的(The row refers to the derived table result for the row with an id value of N. A derived table may result, for example, from a subquery in the FROM clause.)。 <subqueryN>:ID值n的行的物化子查询结果。 4....
The following example returns the query plan for the same query with verbose output: explain verboseselecteventid, eventname,event.venueid, venuenamefromevent, venuewhereevent.venueid = venue.venueid; QUERY PLAN ---{HASHJOIN:startup_cost2.52:total_cost58653620.93:plan_rows8712:plan_width43:best...
Replace invalid characters with dashes, * so that for example "I/O Read Time" becomes "I-O-Read-Time". */static voidExplainXMLTag(const char *tagname, int flags, ExplainState *es){ const char *s; const char *valid = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_."; ...
. As an analogy to the coding world, you can look at the concept of an inner join as very similar to a nested loop. MySQL chooses the table it thinks will be best to start the journey with (the outer "loop") and then touches the next table using the values from the outer "loop"...
EXPLAIN returnsa row of information for each table used in the SELECT statement. It lists thetables in the output in the order that MySQL would read them while processingthe statement. MySQL resolves all joins using a nested-loop join method. Thismeans that MySQL reads a row from the first...
Example: Optimizing Query Performance Using auto_explain in PostgreSQL Prerequisites Log Analytics Workspace: Ensure you have a Log Analytics workspace created. If not, create one in the same region as your PostgreSQL server to minimize latency and costs. ...