DATA labeling

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DATA labeling

At present, polarization labeling for each correlator is stored in the SPECTRAL_WINDOW table, although such information is not properly associated with frequency. Consequently, it is proposed that polarization information be stored in a separate POLARIZATION sub-table, indexed by POLARIZATION_ID. However, rather than add POLARIZATION_ID to MAIN as an additional index, it is proposed that SPECTRAL_WINDOW_ID be replaced by DATA_DESC_ID, which points to a DATA_DESCRIPTION sub-table containing SPECTRAL_WINDOW_ID and POLARIZATION_ID pairs. This structure has the specific advantage that the DATA array shape is completely determined by DATA_DESC_ID, which is an important consideration in tiling and uv-data access. The DATA_DESC sub-table will be small, so that secondary look-ups to determine SPECTRAL_WINDOW_ID from DATA_DESC_ID can take place in memory and will not represent a significant overhead.

Thus, SPECTRAL_WINDOW_ID in MAIN will be replaced by DATA_DESC_ID, as follows:


DATA_DESC_ID        Int        (Data description index)         (Reqd.)

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