obi import: new option --preread to do a first readthrough of the

dataset if it contains huge dictionaries for a much faster import.

python/obitools3/commands/import.pyx

@@ -11,6 +11,7 @@ from obitools3.dms.column.column cimport Column
 from obitools3.dms.obiseq cimport Nuc_Seq
 from obitools3.dms import DMS
 from obitools3.dms.taxo.taxo cimport Taxonomy
+from obitools3.files.uncompress cimport CompressedFile
 
 
 from obitools3.utils cimport tobytes, \
@@ -65,6 +66,14 @@ def addOptions(parser):
     addTaxdumpInputOption(parser)
     addMinimalOutputOption(parser)
 
+    group = parser.add_argument_group('obi import specific options')
+
+    group.add_argument('--preread',
+                     action="store_true", dest="import:preread",
+                     default=False,
+                     help="Do a first readthrough of the dataset if it contains huge dictionaries (more than 100 keys) for "
+                          "a much faster import.")
+
 
 def run(config):
     
@@ -170,8 +179,6 @@ def run(config):
     if entry_count >= 0:
         pb = ProgressBar(entry_count, config, seconde=5)
         
-    entries = input[1]
-        
     NUC_SEQS_view = False
     if isinstance(output[1], View) :
         view = output[1]
@@ -188,6 +195,60 @@ def run(config):
         
     dcols = {}
         
+    # First read through the entries to prepare columns with dictionaries as they are very time-expensive to rewrite
+    if config['import']['preread']:
+        logger("info", "First readthrough...")
+        entries = input[1]
+        i = 0
+        dict_dict = {}
+        for entry in entries:
+            PyErr_CheckSignals()
+        
+            if entry is None:  # error or exception handled at lower level, not raised because Python generators can't resume after any exception is raised
+                if config['obi']['skiperror']:
+                    i-=1
+                    continue
+                else:
+                    raise Exception("obi import error in first readthrough")
+            
+            if pb is not None:
+                pb(i)
+            elif not i%50000:
+                logger("info", "Read %d entries", i)
+    
+            for tag in entry :
+                if type(entry[tag]) == dict :
+                    if tag in dict_dict:
+                        dict_dict[tag][0].update(entry[tag].keys())
+                    else:
+                        dict_dict[tag] = [set(entry[tag].keys()), get_obitype(entry[tag])]
+            i+=1
+        
+        if pb is not None:
+            pb(i, force=True)
+            print("", file=sys.stderr)
+       
+        for tag in dict_dict:
+            dcols[tag] = (Column.new_column(view, tag, dict_dict[tag][1], \
+                              nb_elements_per_line=len(dict_dict[tag][0]), \
+                              elements_names=list(dict_dict[tag][0])), \
+                          value_obitype)
+    
+        
+        # Reinitialize the input
+        if isinstance(input[0], CompressedFile):
+            input_is_file = True
+        if entry_count >= 0:
+            pb = ProgressBar(entry_count, config, seconde=5)
+        try:
+            input[0].close()
+        except AttributeError:
+            pass
+        input = open_uri(config['obi']['inputURI'], force_file=input_is_file)
+        if input is None:
+            raise Exception("Could not open input URI")
+    
+    entries = input[1]
     i = 0
     for entry in entries :