The Has command returns true if the given connection contains a row with the given values in the primary key columns, and false otherwise.

Persistent tables are in general thread safe as of Maple 2021; see the Thread Safety section of the PersistentTable overview page for more details and caveats.

For more information on thread safety, see index/threadsafe.

$\mathrm{with}\left(\mathrm{PersistentTable}\right)$

$\left[\mathrm{Close}\,\mathrm{Count}\,\mathrm{Get}\,\mathrm{GetAll}\,\mathrm{GetKeys}\,\mathrm{Has}\,\mathrm{MaybeGet}\,\mathrm{Open}\,\mathrm{RawCommand}\,\mathrm{Set}\right]$

$\mathrm{connection}≔\mathrm{Open}\left('':memory:''\,\mathrm{style}=\left[\mathrm{k1}::\mathrm{anything}\,\mathrm{k2}::\mathrm{integer}\,v::\mathrm{anything}\,\mathrm{primarykey}=2\right]\right)$

$\mathrm{connection}≔\mathrm{<<\; 3-column\; persistent\; table\; at\; :memory:\; >>}$

$\mathrm{connection}\left[x,3\right]≔y^2$

${\mathrm{connection}}_{x,3}≔y^2$

$\mathrm{connection}\left[z,5\right]≔y^3$

${\mathrm{connection}}_{z,5}≔y^3$

$\mathrm{Has}\left(\mathrm{connection}\&comma;x\&comma;3\right)$

$\mathrm{true}$

$\mathrm{Has}\left(\mathrm{connection}\&comma;a\&comma;4\right)$

$\mathrm{false}$

$\mathrm{Close}\left(\mathrm{connection}\right)$

The PersistentTable[Has] command was introduced in Maple 2021.

For more information on Maple 2021 changes, see Updates in Maple 2021.