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ATLAS Offline Software
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ATLAS Offline Software
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a struct that contains meta-information about each column that's needed to interface the column with the columnar data store More...
#include <ColumnInfo.h>
Public Attributes | |
| std::string | name {} |
| the name of the column More... | |
| unsigned | index = 0u |
| the index of the column in the data array More... | |
| const std::type_info * | type = nullptr |
| the type of the individual entries in the column More... | |
| ColumnAccessMode | accessMode = ColumnAccessMode::input |
| the access mode for the column More... | |
| std::string | offsetName {} |
| the name of the offset column used for this column (or empty string for none) More... | |
| std::vector< unsigned > | fixedDimensions {} |
| the fixed dimensions this column has (if any) More... | |
| bool | isOffset = false |
| whether this is an offset column More... | |
| std::string | replacesColumn {} |
| whether this replaces another column More... | |
| bool | isOptional = false |
| whether this column is optional More... | |
| std::vector< std::string > | linkTargetNames {} |
| for link columns: the name(s) of the container(s) we link to More... | |
| std::string | variantLinkKeyColumn {} |
| if this is a variant link column, this is the name of the column with the container keys More... | |
a struct that contains meta-information about each column that's needed to interface the column with the columnar data store
Definition at line 34 of file ColumnInfo.h.
| ColumnAccessMode columnar::ColumnInfo::accessMode = ColumnAccessMode::input |
the access mode for the column
Definition at line 58 of file ColumnInfo.h.
| std::vector<unsigned> columnar::ColumnInfo::fixedDimensions {} |
the fixed dimensions this column has (if any)
For the most part we use dynamic dimensions via offset maps, but sometimes the dimensions are hard-coded, which then uses these dimensions.
Definition at line 82 of file ColumnInfo.h.
| unsigned columnar::ColumnInfo::index = 0u |
the index of the column in the data array
Definition at line 46 of file ColumnInfo.h.
| bool columnar::ColumnInfo::isOffset = false |
whether this is an offset column
In part this is for consistency checks, i.e. other columns can only refer to this as an offset column if this is set. It also means that there needs to be an extra element in the column past the last "regular" one to hold the total number of entries in columns using this.
Definition at line 92 of file ColumnInfo.h.
| bool columnar::ColumnInfo::isOptional = false |
whether this column is optional
Essentially this indicates that the column can be skipped, and the tool will check whether the column is present before trying to use it. This allows to adapt the tool somewhat to different environments.
The downside here is that overall this is still a bit ambiguous, i.e. whoever links up the columns needs to decide whether it is needed. For columns that are not in the input file that's easy, there is no choice but omitting them. However, some columns only exist as a backup option for other columns, and ideally we don't want to load the backup columns when the main columns are missing. So either that needs to be set during configuration, or we need to add more meta-information for that case, or the user needs to do something smart (i.e. manual) in their code.
Definition at line 121 of file ColumnInfo.h.
| std::vector<std::string> columnar::ColumnInfo::linkTargetNames {} |
for link columns: the name(s) of the container(s) we link to
Some of our columns contain links to other objects. For those columns this will contain the names of the containers we link to (i.e. the names of their offset columns).
For simple link columns that can only link to a single other container, this will be a vector of length one and variantLinkKeyColumn will not be set. In that case the link column will simply contain the index of the object in the linked too container.
For variant link columns (i.e. columns with links that can reference objects in more than one container), this will contain the list of all linked to columns that this tool will use. In that case the most significant bits of the index in this column will encode a container key that is matched against variantLinkKeyColumn to identify which container is being referenced by each link.
Note that a variant link column may contain links to columns that are not listed here, but those will not be used by this tool. There are also no requirements on the exact values of the keys, as long as they match variantLinkKeyColumn. And different tools may list the columns in different order. The thought behind that is that it allows multiple tools to read the same link column as long as they have each a unique key column, without having to coordinate the exact list of linked containers used.
Definition at line 154 of file ColumnInfo.h.
| std::string columnar::ColumnInfo::name {} |
the name of the column
This is the primary way by which columns should be identified when interacting with the user, but it should only be used during the configuration. During the actual processing this should rely on the index for identification instead.
Definition at line 42 of file ColumnInfo.h.
| std::string columnar::ColumnInfo::offsetName {} |
the name of the offset column used for this column (or empty string for none)
Most of our columns do not represent a regular-shaped tensor, but has a different number of entries in each row, e.g. the column holding the muon-pt will have a different number of muons per event. To handle this, there needs to be a column that contains the offsets for each row.
There can be multiple irregularly shaped dimensions for a column, in which case this is just the name of the inner-most one. The outer-ones can be found by following the offset name in a chain.
Definition at line 74 of file ColumnInfo.h.
| std::string columnar::ColumnInfo::replacesColumn {} |
whether this replaces another column
For corrections it is quite typical that a column is meant to replace another column. In columnar land we will create genuinely new columns, in xAOD land we will usually overwrite the content of those columns. This member is used to indicate which column gets replaced.
Definition at line 102 of file ColumnInfo.h.
| const std::type_info* columnar::ColumnInfo::type = nullptr |
the type of the individual entries in the column
This should generally be something like float or int, neither be const-qualified nor in a container like std::vector<float>.
Definition at line 54 of file ColumnInfo.h.
| std::string columnar::ColumnInfo::variantLinkKeyColumn {} |
if this is a variant link column, this is the name of the column with the container keys
If set, this is the name of another column that should have exactly one entry per entry in linkTargetNames, giving the container keys for each.
This doesn't have to be set for simple link columns that only point to a single container. In that case the link column will simply contain indices without keys (a.k.a. all keys are zero). That is actually the more common case, which is also simpler to handle in columnar code.
Definition at line 169 of file ColumnInfo.h.
1.8.18