The Get command retrieves the row in the table given by the connection object that has the values in keys as its primary key, and returns the values that are not part of the primary key. If no such row exists, then it generates an error.

Indexing the connection object with keys is equivalent to calling Get.

The MaybeGet command retrieves the row in the table given by the connection object that has the values in keys as its primary key, and returns the values that are not part of the primary key. If no such row exists, then it returns default.

The Set command enters a new row into the connection object, or modifies an existing row, depending on whether a row with the given keys exists.

Assigning to a connection object indexed with keys is equivalent to calling Set.

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.

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

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

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

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

$\mathrm{Set}\left(\mathrm{connection}\&comma;\left[x\&comma;3\right]\&comma;y^2\right)$

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

${\mathrm{connection}}_{z,5}≔y^3$

$\mathrm{Get}\left(\mathrm{connection}\&comma;\left[x\&comma;3\right]\right)$

$y^2$

$\mathrm{connection}\left[z,5\right]$

$y^3$

$\mathrm{MaybeGet}\left(\mathrm{connection}\&comma;\left[z\&comma;5\right]\&comma;1\right)$

$y^3$

$\mathrm{Get}\left(\mathrm{connection}\&comma;\left[a\&comma;4\right]\right)$

Error, (in PersistentTable:-Get) bad index into PersistentTable

$\mathrm{connection}\left[a,4\right]$

Error, bad index into PersistentTable

$\mathrm{MaybeGet}\left(\mathrm{connection}\&comma;\left[a\&comma;4\right]\&comma;1\right)$

$1$

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

The PersistentTable[Get], PersistentTable[MaybeGet] and PersistentTable[Set] commands were introduced in Maple 2021.

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