db2 执行计划的解读
db2exfmt o Table Operators
db2exfmt TBSCAN - Table Scan
db2exfmt IXSCAN - Index Scan
db2exfmt FETCH - Fetch from Table
db2exfmt
db2exfmt o Joins
db2exfmt MSJOIN - Merge Scan Join
db2exfmt NLJOIN - Nested Loop Join
db2exfmt HSJOIN - Hash Join
db2exfmt
db2exfmt o Aggregation
db2exfmt GRPBY - Group By
db2exfmt SUM - Sum
db2exfmt AVG - Average
db2exfmt MIN - Minimum
db2exfmt MAX - Maximun
db2exfmt etc.
db2exfmt
db2exfmt o Temp / Sort
db2exfmt TEMP - Insert into temp table
db2exfmt SORT - Sort
db2exfmt
db2exfmt o Special Operations
db2exfmt IXAND - Index ANDing
db2exfmt RIDSCA - Index ORing or List Prefetch
db2exfmt IXA - Star Schema Bitmap Indexing
db2exfmt BTQ - Broadcast Table Queue
db2exfmt DTQ - Directed Table Queue
db2exfmt MBTQ - Merge Broadcast Table Queue
db2exfmt MDTQ - Merge Directed Table Queue
db2exfmt LTQ - Local Table Queue, for Intra-partition parallelism
+-------------------------------+-----------------------+-----------------------+
| Join Strategy | Inner Table | Outer Table |
+-------------------------------+-----------------------+-----------------------+
| Collocated Join | Temporary Table | Temporary Table |
+-------------------------------+-----------------------+-----------------------+
| Directed Inner Join | Temporary Table | Hashed Table Queue |
| Directed Outer Join | Hashed Table Queue | Temporary Table |
| Directed Inner and Outer Join | Hashed Table Queue | Hashed Table Queue |
+-------------------------------+-----------------------+-----------------------+
| Broadcast Inner Join | Temporary Table | Broadcast Table Queue |
| Boradcast Outer Join | Broadcast Table Queue | Temporary Table |
+-------------------------------+-----------------------+-----------------------+
附:
| BTQ | Broadcast Table Queue broadcasts data to several partitions. |
| DELETE | Deletes rows from a table. |
| DTQ | Directed Table Queue transfers data to a specific partition. |
| EISCAN | Scans a user-defined index to produce a reduced stream of rows. |
| FETCH | Fetches columns from a table using spe-cific record identifier. |
| FILTER | Represents the application of residual predicates. |
| GRPBY | Groups rows by common values of desig-nated columns or functions. |
| HSJOIN | Represents a hash join, where two or more tables are hashed on join columns. |
| INSERT | Inserts rows into a table. |
| IXAND | ANDs together the row identifiers (RIDs) from two or more index scans. |
| IXSCAN | Scans an index of a table with optional start/stop conditions, producing an ordered stream of rows. |
| LTQ | Local Table Queue. Transfers data between local agents. |
| LMTQ | Local Merge Table Queue. Merges data transferred between local agents. |
| MBTQ | Merging Broadcast Table Queue. |
| MDTQ | Merging Directed Table queue. |
| MSJOIN | Represents a merge join, where both outer and inner tables must be in join-predicate order. |
| NLJOIN | Represents a nested loop join that accesses an inner table once for each row of the outer table. |
| RETURN | Represents the return of data from the query to the user. |
| RIDSCAN | Scans a list of row identifiers (RIDs) obtained from one or more indexes. |
| RPD | For nonrelational wrappers, it shows the simulated SQL operation that the nonrela-tional wrapper will be asked to perform. |
| SHIP | Retrieves data from a remote database source. Used in federated systems. |
| SORT | Sorts rows in the order of specified col-umns, and optionally eliminates duplicate entries. |
| TBSCAN | Retrieves rows by reading all required data directly from the data pages. |
| TEMP | Stores data in a temporary table to be read back out (possibly multiple times). |
| TQUEUE | Transfers table data between agents. |
| UNION | Concatenates streams of rows from multi-ple tables. |
| UNIQUE | Eliminates rows with duplicate values, for specified columns. |
| UPDATE | Updates rows in a table. |
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/694276/viewspace-184341/ ，如需转载，请注明出处，否则将追究法律责任。
